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Sample records for laser induced glaucoma

  1. Pattern-evoked potentials and optic nerve fiber loss in monocular laser-induced glaucoma

    SciTech Connect

    Johnson, M.A.; Drum, B.A.; Quigley, H.A.; Sanchez, R.M.; Dunkelberger, G.R.

    1989-05-01

    ERG and VEP responses to counterphase checkerboard stimuli were obtained from cynomolgus monkeys with monocular glaucoma induced by laser photocoagulation of the trabecular meshwork. The glaucomatous eyes showed reductions of PERG amplitude that were directly related to the histologically defined nerve damage. VEP amplitudes were also reduced in the glaucomatous eyes, but were more variable and less affected by damage than the PERG responses. An acute increase in eye pressure to 40 mm Hg in eyes without damage had no detectable effect on PERG amplitudes.

  2. Scanning laser polarimetry in glaucoma

    PubMed Central

    Dada, Tanuj; Sharma, Reetika; Angmo, Dewang; Sinha, Gautam; Bhartiya, Shibal; Mishra, Sanjay K; Panda, Anita; Sihota, Ramanjit

    2014-01-01

    Glaucoma is an acquired progressive optic neuropathy which is characterized by changes in the optic nerve head and retinal nerve fiber layer (RNFL). White-on-white perimetry is the gold standard for the diagnosis of glaucoma. However, it can detect defects in the visual field only after the loss of as many as 40% of the ganglion cells. Hence, the measurement of RNFL thickness has come up. Optical coherence tomography and scanning laser polarimetry (SLP) are the techniques that utilize the evaluation of RNFL for the evaluation of glaucoma. SLP provides RNFL thickness measurements based upon the birefringence of the retinal ganglion cell axons. We have reviewed the published literature on the use of SLP in glaucoma. This review elucidates the technological principles, recent developments and the role of SLP in the diagnosis and monitoring of glaucomatous optic neuropathy, in the light of scientific evidence so far. PMID:25494244

  3. Ultrastructural and pharmacologic studies on laser-induced glaucoma in primates and rabbits

    SciTech Connect

    March, W.F.; Gherezghiher, T.; Koss, M.; Nordquist, R.

    1984-01-01

    Sustained high intraocular pressure resulting in optic nerve cupping and loss of ganglion cells was produced in five rhesus monkeys and eight pigmented rabbits by applying argon laser energy to the trabecular meshwork. In addition, the rabbits manifested buphthalmus. Flow of carbon particles subsequently injected into the anterior chamber was obstructed at the trabecular meshwork by a wound-healing response that closed the intratrabecular spaces. Besides this sustained high intraocular pressure as a result of late scarring, an acute hypertensive response was seen in all rabbits which may correspond to the acute hypertension seen after laser trabeculoplasty in humans. The acute hypertensive response could be only partially blocked by prostaglandin inhibitors and the authors believe that prostaglandins are not primarily responsible for this effect. Medications known to lower intraocular pressure were systematically tested in both glaucoma models.

  4. Lasers in the treatment of glaucoma

    NASA Astrophysics Data System (ADS)

    Kecik, Tadeusz

    1995-03-01

    The task of the laser methods of glaucoma treatment used up to the present day is to reduce the intraocular pressure. They are the modification of the surgical procedures. The radiation of the laser is the tool that enables us to perform the procedure in a more precise and safe manner. Most of the procedures are ambulatory, thus, making the expenses for the treatment lower. The results of the treatment are satisfactory, and in many cases, enable the patient to avoid surgical procedures. In practice, for the anti-glaucoma procedures the argon laser, YAG Nd+3, of free generation, and Q-switch, Holm laser, are being used. The perspectives to use other lasers also exist.

  5. Copper vapor laser prospects in glaucoma treatment

    NASA Astrophysics Data System (ADS)

    Nesterov, Arcady P.; Novoderezhkin, Vladimir I.; Egorov, Alexey E.; Shaban, Naim; Ponomarev, Igor V.

    1996-05-01

    New advances of copper vapor laser (CVL-laser) have been studied. Two wavelength radiation of the laser (511 nm and 578 nm) gives deeper permeability into organic tissues. Besides, the short pulse prevents the warm relaxation of small vessels. The technical data of CVL-laser: operating regime -- pulse, pulse duration -- 20 ns, pulse frequency 15000 pulse/sec. The shutter works in intervals from 0.05 to 2.0 sec. The power varies in accordance with wavelength: 511 nm (green) -- 1.5 W, 578 nm (yellow) -- 1, 2 W. The diameter of coagulate may be different: 100, 150, 400, 1000 mkm. We chose CVL-laser 'Femta,' created by P. N. Lebedev Physical Institute of RAS, for ophthalmological use. Thirty eight eyes of 37 patients with different types and stages of glaucoma were studied and treated with CVL-laser. The operations of photomydriasis, gonioplasty and trabeculoplasty have been performed. CVL- laser demonstrated efficient application in treatment of interior eye segment of glaucoma patients. The advantages and disadvantages of the CVL-laser application in glaucoma surgery were discussed.

  6. Animal models of glucocorticoid-induced glaucoma.

    PubMed

    Overby, Darryl R; Clark, Abbot F

    2015-12-01

    Glucocorticoid (GC) therapy is widely used to treat a variety of inflammatory diseases and conditions. While unmatched in their anti-inflammatory and immunosuppressive activities, GC therapy is often associated with the significant ocular side effect of GC-induced ocular hypertension (OHT) and iatrogenic open-angle glaucoma. Investigators have generated GC-induced OHT and glaucoma in at least 8 different species besides man. These models mimic many features of this condition in man and provide morphologic and molecular insights into the pathogenesis of GC-OHT. In addition, there are many clinical, morphological, and molecular similarities between GC-induced glaucoma and primary open-angle glaucoma (POAG), making animals models of GC-induced OHT and glaucoma attractive models in which to study specific aspects of POAG.

  7. Glaucoma

    MedlinePlus

    ... version of this page please turn Javascript on. Glaucoma What is Glaucoma? Glaucoma is a group of diseases that can ... is much greater for people over 60. How Glaucoma Develops There are several different types of glaucoma. ...

  8. Light-induced avian glaucoma as an animal model for human primary glaucoma.

    PubMed

    Lauber, J K

    1987-01-01

    Glaucoma can be induced in domestic chicks at the will of the investigator, by the simple device of rearing the chicks under continuous light. This light-induced avian glaucoma (LIAG) is presented as an animal model system for human open-angle glaucoma. A number of morphological and physiological findings in LIAG are reviewed, and the LIAG system is compared with several other glaucoma model systems, in dogs, rabbits and monkeys. Intraocular pressure in LIAG has been demonstrated to be responsive to several anti-glaucoma drugs, and the system could be used for further drug testing. Thus it is suggested that LIAG may be especially useful in studies seeking to understand human glaucoma, and how to forestall it, or treat it. As well, a prolonged "pre-glaucoma" period is available to the investigator working with LIAG, during which a pathological course is already underway in the eye, but intraocular pressure has not yet gone up. PMID:3332676

  9. Experimental Contact Lens to Prevent Glaucoma-Induced Blindness

    MedlinePlus

    ... Articles | Inside Life Science Home Page An Experimental Contact Lens to Prevent Glaucoma-Induced Blindness By Sharon Reynolds Posted January 23, 2014 An experimental contact lens design releases a glaucoma medicine at a ...

  10. Current and Future of Laser Therapy in the Management of Glaucoma

    PubMed Central

    Ekici, Feyzahan; Waisbourd, Michael; Katz, L. Jay

    2016-01-01

    There has been tremendous progress in the past decades in the utilization of lasers for treating patients with glaucoma. This article reviews the use of lasers in different areas of glaucoma, including the shift from argon laser trabeculoplasty (ALT) to selective laser trabeculoplasty (SLT), laser trabeculoplasty as an initial treatment for glaucoma, new laser trabeculoplasty procedures under investigation, and other recent laser treatment modalities such as endoscopic cyclophotocoagulation and laser-assisted deep sclerectomy. PMID:27014388

  11. Confocal scanning laser ophthalmoscopy in glaucoma diagnosis and management.

    PubMed

    Alexandrescu, C; Dascalu, A M; Panca, A; Sescioreanu, A; Mitulescu, C; Ciuluvica, R; Voinea, L; Celea, C

    2010-01-01

    The early diagnosis and detection of progression are two key-elements in the actual management of glaucoma. The current opinion in clinical practice is to quantify the structural damage for a better follow-up of the patient and the standardization of the results. The present review is a concise survey of literature covering the period of 1990-2010, documenting the evidence-based role of confocal scanning laser ophthalmoscopy in glaucoma diagnosis and management.

  12. Experimentally Induced Mammalian Models of Glaucoma

    PubMed Central

    Yoshitomi, Takeshi; Zorumski, Charles F.; Izumi, Yukitoshi

    2015-01-01

    A wide variety of animal models have been used to study glaucoma. Although these models provide valuable information about the disease, there is still no ideal model for studying glaucoma due to its complex pathogenesis. Animal models for glaucoma are pivotal for clarifying glaucoma etiology and for developing novel therapeutic strategies to halt disease progression. In this review paper, we summarize some of the major findings obtained in various glaucoma models and examine the strengths and limitations of these models. PMID:26064891

  13. Transscleral laser cyclocoagulation in treatment of noncompensated glaucoma

    NASA Astrophysics Data System (ADS)

    Bakutkin, Valery V.; Karimov, Ravil N.; Tcherviakova, Olga V.

    2001-05-01

    The object of the present study is to estimate the impact of transscleral laser cyclocoagulation as a treatment for patients with non-compensated glaucoma and low visual functions. The effectiveness of the given treatment is estimated by the use of multiple statistical methods, including correlation, multiple regression and discriminant analysis. The results meaningfully confirm the effectiveness of laser surgery in non-compensated open-angle (stage III) glaucoma treatment, whilst the developed mathematical model of correlation between intra-eye liquid production and key operation parameters can be successfully used to control the process of liquid production.

  14. Laser Activated Flow Regulator for Glaucoma Drainage Devices

    PubMed Central

    Olson, Jeffrey L.; Velez-Montoya, Raul; Bhandari, Ramanath

    2014-01-01

    Purpose To assess the capabilities of a new glaucoma drainage device regulator in controlling fluid flow as well as to demonstrate that this effect may be titratable by noninvasive means. Methods A rigid eye model with two main ports was used. On the first port, we placed a saline solution column. On the second, we placed a glaucoma shunt. We then measured the flow and flow rate through the system. After placing the regulator device on the tip of the tube, we measured again with the intact membrane and with the membrane open 50% and 100%. For the ex vivo testing we used a similar setting, using a cadaveric porcine eye, we measured again the flow and flow rate. However, this time we opened the membrane gradually using laser shots. A one-way analysis of variance and a Fisher's Least Significant Difference test were used for statistical significance. We also calculated the correlation between the numbers of laser shots applied and the main outcomes. Results The flow through the system with the glaucoma drainage device regulator (membrane intact and 50% open) was statistically lower than with the membrane open 100% and without device (P < 0.05). The flow was successfully controlled by the number of laser shots applied, and showed a positive correlation (+ 0.9). The flow rate was almost doubled every 10 shots and statistically lower than without device at all time (P < 0.05). Conclusions The glaucoma drainage device regulator can be controlled noninvasively with laser, and allows titratable control of aqueous flow. Translational Relevance Initial results and evidence from this experiment will justify the initiation of in vivo animal trials with the glaucoma drainage device regulator; which brings us closer to possible human trials and the chance to significantly improve the existing technology to treat glaucoma surgically. PMID:25374772

  15. [Diagnosis of open-angle glaucoma after myopic excimer laser corneal refractive surgery].

    PubMed

    Wu, Ling-ling

    2013-11-01

    Patients with high myopia are at high risk of glaucoma and are difficult to be discovered at early stage in the case of existing glaucoma. Myopic excimer laser corneal refractive surgery changes the structure of the eye, which makes early glaucoma diagnosis more difficult. Furthermore, refractive surgery may aggravate existing condition of glaucoma. To prevent the exacerbation of glaucoma, it is great important to perform the preoperative glaucoma risk assessment. In this paper, we presented the key diagnostic points of glaucoma assessment before and after excimer laser refractive surgery and discussed the postoperative intraocular pressure measurements and its impact on the diagnosis and treatment of glaucoma including characterization of open angle glaucoma and long-term follow up in patients with high myopia.

  16. Glaucoma

    MedlinePlus

    ... YouTube Videos > NEI YouTube Videos: Glaucoma NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia ... of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Glaucoma NEI on Twitter NEI on YouTube NEI ...

  17. Glaucoma.

    PubMed

    Mantravadi, Anand V; Vadhar, Neil

    2015-09-01

    Glaucoma is a multifactorial degenerative optic neuropathy that can progress at variable rates and afflict all age groups. It is the second leading cause of blindness worldwide. The disease is commonly divided into 2 major subtypes, open angle and angle closure. Diagnosis of glaucoma is made by a combination of identifying characteristic changes of the optic nerve, functional testing such as visual fields, and structural imaging of the optic nerve. Management is aimed at reducing intraocular pressure (IOP). Patients with known risk factors should be referred to an ophthalmologist for complete evaluation.

  18. Head-down posture induces PERG alterations in early glaucoma

    PubMed Central

    Ventura, Lori M.; Golubev, Iuri; Lee, William; Nose, Izuru; Parel, Jean-Marie; Feuer, William J.; Porciatti, Vittorio

    2011-01-01

    Purpose To probe susceptibility of retinal ganglion cells (RGC) to physiological stressors associated with moderate head-down body tilt in patients with suspicion of glaucoma or early manifest glaucoma. Methods One hundred nine subjects with best corrected visual acuity ≥20/20 and no disease other than glaucoma (glaucoma suspects, GS= 79, early manifest glaucoma, EMG=14, normal controls, NC= 16) and comparable age range were tested. Non-contact IOP, pattern electroretinogram (PERG), and brachial blood pressure/heart rate measurements were performed in three consecutive (~8 minutes apart) conditions: seated (baseline), −10 deg whole body head-down (HDT), and seated again (recovery). PERG amplitude and latency, IOP, and systolic/diastolic blood pressures, heart rate, calculated mean central retinal artery pressure, ocular perfusion pressure, and systolic/diastolic perfusion pressures were evaluated. Results During HDT, IOP significantly (P<0.001) increased in all groups approximately to the same extent (~20%). PERG amplitude did not change in NC but decreased significantly (P<0.001) in patients (GS, −25%, EMG −23%). PERG phase become delayed in NC (− 1.6%, P=0.04) but more so in patients (GS, −2.7%, P<0.001; EMG, −6.0%, P<0.001). The proportion of patients with PERG alterations significantly (P<0.05) exceeding those occurring in age- and baseline-adjusted NC were, GS: amplitude 20%, phase 15%; EMG: amplitude 14%, phase 50%. All measures recovered baseline values after HDT. Conclusions Moderate HDT induces temporary worsening of RGC function in a subpopulation of GS and EMG patients. This non-invasive protocol may help disclose abnormal susceptibility of RGCs in a subset of the patients at risk of glaucoma. PMID:22138883

  19. Selective Laser Trabeculoplasty as Primary Treatment for Open-Angle Glaucoma.

    PubMed

    Kadasi, Laith M; Wagdi, Safa; Miller, Kimberly V

    2016-06-01

    Open-angle glaucoma is a silent, chronic disorder which results in progressive and permanent vision loss. Designing the optimal treatment regimen can be particularly challenging in the management of high-risk patients with frequent loss to follow-up or a longstanding history of medication noncompliance. In this article we aim to review fundamental techniques in glaucoma diagnosis and treatment with emphasis on the strengths and weaknesses of selective laser trabeculoplasty, a technique in modern therapy which may mold the future of primary treatment in open angle glaucoma management. [Full article available at http://rimed.org/rimedicaljournal-2016-06.asp, free with no login].

  20. Interface Fluid Syndrome Induced by Uncontrolled Intraocular Pressure Without Triggering Factors After LASIK in a Glaucoma Patient: A Case Report.

    PubMed

    Shoji, Nobuyuki; Ishida, Akira; Haruki, Takahiro; Matsumura, Kazuhiro; Kasahara, Masayuki; Shimizu, Kimiya

    2015-09-01

    This study sought to describe a glaucoma patient with interface fluid syndrome (IFS) induced by uncontrolled intraocular pressure (IOP) without triggering factors after laser in situ keratomileusis (LASIK). Case report and review of the literature. A 23-year-old man with open-angle glaucoma underwent bilateral LASIK for myopia in 2009. Two years later, the patient reported sudden vision loss. The IOP in the right eye was not measurable using Goldmann applanation tonometry (GAT), but was determined to be 33.7 mm Hg using a noncontact tonometer. IFS was diagnosed based on the presence of space-occupying interface fluid on anterior segment optical coherence tomography images. After a trabeculectomy was performed, the IOP decreased to 10 mm Hg, and GAT measurement became possible. However, the corneal fold remained visible in the flap interface. Six months later, the IOP in the left eye increased, and a trabeculectomy was performed during the early stages of this increase in IOP. Following this procedure, the IOP decreased, and visual acuity remained stable. In glaucoma cases that involve a prior increase in IOP, IOP can continue to increase during the disease course even if temporary control of IOP has been achieved. If LASIK is performed in such cases, the treatment of glaucoma becomes insufficient because of underestimation of the typical IOP. In fact, the measurement of IOP can become difficult because of high-IOP levels. Therefore, LASIK should not be performed on patients with glaucoma who are at high risk of elevated IOP.

  1. Scanning laser polarimetry of the peripapillar retinal nerve fiber layer in glaucoma cases

    NASA Astrophysics Data System (ADS)

    Janiec, Slawomir; Rzendkowski, Marek; Gierek-Ciaciura, Stanislawa; Szymkowiak, Monika; Momot-Kawalska, Barbara

    1998-10-01

    Scanning laser polarimetry is the method of evaluating the thickness of the retinal nerve fiber layer. Different pathologies damage retinal fibers, but in glaucoma the damage is present very often before other symptoms reveal. As the earliest possible diagnosis of glaucoma is essential for treatment results, scanning laser polarimetry offers a very useful diagnostic tool for ophthalmology. This paper describes the principles of the method and discusses the results obtained in 50 glaucomatous eyes in conjunction with 2- and 3-D topographical parameters of the optic disc.

  2. Bilateral, Simultaneous, Acute Angle Closure Glaucoma in Pseudophakia Induced by Chlorthalidone

    PubMed Central

    Durai, Indra; Mohan Dhavalikar, Mrunali; Anand, Chandran Prem; Ganesh, Venkatraman; Krishnadas, Ramaswami

    2016-01-01

    Purpose. To report two persons with acute, bilateral, and simultaneous angle closure glaucoma in pseudophakia secondary to uveal effusions induced by administration of chlorthalidone. Methods. Case reports. Results. Bilateral shallow anterior chambers and high intraocular pressure with decline in visual acuity were reported in two patients within days of intake of chlorthalidone for systemic hypertension. Gonioscopy confirmed appositional angle closure while choroidal detachment and ciliochoroidal detachment were revealed on ultrasonographic studies. Discontinuing chlorthalidone and institution of aqueous suppressants to reduce IOP and cycloplegics reversed angle closure and glaucoma. Conclusions. Reports of angle closure glaucoma in pseudophakic eyes induced by idiosyncratic reaction to chlorthalidone confirms that osmotic changes in the crystalline lens has no role in the pathogenesis of drug induced glaucoma and reaffirms that glaucoma is secondary to ciliochoroidal detachment and ciliary body rotation and edema. PMID:27274878

  3. Femtosecond laser for glaucoma treatment: the comparison between simulation and experimentation results on ocular tissue removal

    NASA Astrophysics Data System (ADS)

    Hou, Dong Xia; Ngoi, Bryan K. A.; Hoh, Sek Tien; Koh, Lee Huat K.; Deng, Yuan Zi

    2005-04-01

    In ophthalmology, the use of femtosecond lasers is receiving more attention than ever due to its extremely high intensity and ultra short pulse duration. It opens the highly beneficial possibilities for minimized side effects during surgery process, and one of the specific areas is laser surgery in glaucoma treatment. However, the sophisticated femtosecond laser-ocular tissue interaction mechanism hampers the clinical application of femtosecond laser to treat glaucoma. The potential contribution in this work lies in the fact, that this is the first time a modified moving breakdown theory is applied, which is appropriate for femtosecond time scale, to analyze femtosecond laser-ocular tissue interaction mechanism. Based on this theory, energy deposition and corresponding thermal increase are studied by both simulation and experimentation. A simulation model was developed using Matlab software, and the simulation result was validated through in-vitro laser-tissue interaction experiment using pig iris. By comparing the theoretical and experimental results, it is shown that femtosecond laser can obtain determined ocular tissue removal, and the thermal damage is evidently reduced. This result provides a promising potential for femtosecond laser in glaucoma treatment.

  4. Correlation between frequency doubling technology perimetry and scanning laser polarimetry in glaucoma suspects and glaucomatous eyes.

    PubMed

    Kim, Su Hyun; Hong, Hunei; Koo, Hee Jo; Yang, Sung-jae; Tchah, Hungwon; Kook, Michael S

    2004-12-01

    The aim of this study was to determine the relationship between the frequency doubling technology (FDT) screening algorithm and parapapillary retinal nerve fiber layer (RNFL) thickness in the eyes of glaucoma suspects and patients with open angle glaucoma. FDT C20-1 screening program and a scanning laser polarimetry (SLP) system (GDx-NFA) was used to assess 53 glaucomatous eyes, 53 glaucoma suspects and 36 normal control eyes. In glaucomatous eyes, there were correlations between the FDT the screening algorithm and RNFL retardation values in several polarimetric indices, most significantly "inferior thickness" (r = -0.321, P = 0.029). In the eyes of glaucoma suspects, however, we observed no correlation between the FDT results and RNFL retardation values (r = 0.080, P > 0.05, "inferior thickness"). In glaucomatous eyes, the abnormal scores obtained with FDT screening program correlated negatively with RNFL retardation values, as measured by SLP. Despite poor correlation between the FDT abnormal score and RNFL retardation value in glaucoma suspects, detection of abnormality using the FDT screening protocol may aid in the assessment of early glaucomatous structural damage. PMID:15635821

  5. Glaucoma-induced degeneration of retinal ganglion cells prevented by hypoxic preconditioning: a model of glaucoma tolerance.

    PubMed

    Zhu, Yanli; Zhang, Lihong; Schmidt, Jimena F; Gidday, Jeffrey M

    2012-01-01

    Like all cells, neurons adapt to stress by transient alterations in phenotype, an epigenetic response that forms the basis for preconditioning against acute ischemic injury in the central nervous system. We recently showed that a modified repetitive hypoxic preconditioning (RHP) regimen significantly extends the window of ischemic tolerance to acute retinal ischemic injury from days to months. The present study was undertaken to determine if this uniquely protracted neuroprotective phenotype would also confer resistance to glaucomatous neurodegeneration. Retinal ganglion cell death at somatic and axonal levels was assessed after both 3 and 10 wks of sustained intraocular hypertension in an adult mouse model of inducible, open-angle glaucoma, with or without RHP before intraocular pressure elevation. Loss of brn3-positive ganglion cell soma after 3 wks of experimental glaucoma, along with increases in several apoptotic endpoints, were all significantly and robustly attenuated in mice subjected to RHP. Soma protection by RHP was also confirmed after 10 wks of intraocular hypertension by brn3 and SMI32 immunostaining. In addition, quantification of axon density in the postlaminar optic nerve documented robust preservation in RHP-treated mice, and neurofilament immunostaining also revealed preconditioning-induced improvements in axon integrity/survival in both retina and optic nerve after 10 wks of experimental glaucoma. This uniquely protracted period of phenotypic change, established in retinal ganglion cells by the activation of latent antiapoptotic, prosurvival mechanisms at both somatic and axonal levels, reflects a novel form of inducible neuronal plasticity that may provide innovative therapeutic targets for preventing and treating glaucoma and other neurodegenerative diseases. PMID:22396016

  6. A nanopore membrane regulator device for laser modulated flow after glaucoma surgery.

    PubMed

    Olson, Jeffrey L; Bhandari, Ramanath; Groman-Lupa, Sergio; Velez-Montoya, Raul

    2015-10-01

    Glaucoma, the second most common cause of blindness in the world, is a multifactorial disease with several risk factors, of which intraocular pressure (IOP) is a primary contributing factor. Filtration surgery is one of the most effective means to significantly lower IOP compared to medical or laser treatments, and it is typically reserved for advanced disease. However, there are high rates of postoperative complications associated with the procedure, often from over- or under-filtration. To address these problems, the glaucoma drainage device regulator (GDDR) implant was developed to allow post-operative control of aqueous flow and IOP. The device, a tube with a nanopore membrane, is placed beneath the scleral flap. Postoperatively, the membrane surface can be ruptured with a laser to augment flow through the system. This feature allows adjustable control of aqueous flow and diminishes the risk of hypotony in the early postoperative period. PMID:26272497

  7. A nanopore membrane regulator device for laser modulated flow after glaucoma surgery.

    PubMed

    Olson, Jeffrey L; Bhandari, Ramanath; Groman-Lupa, Sergio; Velez-Montoya, Raul

    2015-10-01

    Glaucoma, the second most common cause of blindness in the world, is a multifactorial disease with several risk factors, of which intraocular pressure (IOP) is a primary contributing factor. Filtration surgery is one of the most effective means to significantly lower IOP compared to medical or laser treatments, and it is typically reserved for advanced disease. However, there are high rates of postoperative complications associated with the procedure, often from over- or under-filtration. To address these problems, the glaucoma drainage device regulator (GDDR) implant was developed to allow post-operative control of aqueous flow and IOP. The device, a tube with a nanopore membrane, is placed beneath the scleral flap. Postoperatively, the membrane surface can be ruptured with a laser to augment flow through the system. This feature allows adjustable control of aqueous flow and diminishes the risk of hypotony in the early postoperative period.

  8. Ab interno laser sclerostomy in aphakic patients with glaucoma and chronic inflammation.

    PubMed

    Wilson, R P; Javitt, J C

    1990-08-15

    Five patients with aphakia, glaucoma, and chronic inflammation were treated with ab interno sclerostomy by using the continuous wave Nd:YAG laser focused through a sapphire probe. After a follow-up period of 24 to 28 months, three of five patients had good intraocular pressure control. The sclerostomy failed in one patient when it was occluded by vitreous. The second failure was attributed to closure of the sclerostomy because of chronic intraocular inflammation.

  9. Retinal ganglion cell protection with geranylgeranylacetone, a heat shock protein inducer, in a rat glaucoma model.

    PubMed Central

    Caprioli, Joseph; Ishii, Yoko; Kwong, Jacky M K

    2003-01-01

    PURPOSE: To study the effects of geranylgeranylacetone (GCA) on the expression of inducible (HSP72) and constitutive (HSC70) heat shock proteins (HSPs) on retinal ganglion cells (RGCs) in a rat model of glaucoma. METHODS: Adult Wistar rats were given intraperitoneal injections of GGA, 200 mg/kg daily. Western blot analysis and immunohistochemical staining for HSP72 and HSC70 were performed after 1, 3, and 7 days of GGA administration. After 7 days of GGA pretreatment, intraocular pressure (IOP) was elevated unilaterally by repeated trabecular argon laser photocoagulation 5 days after intracameral injection of india ink. After the first laser photocoagulation, CGA was given twice a week. RGC survival was evaluated after 5 weeks of IOP elevation. Immunohistochemistry and TdT-mediated biotin-dUTP nick end labeling (TUNEL) were performed after 1 week of IOP elevation. Quercetin, an inhibitor of HSP expression, was also administered to a separate group. RESULTS: There was increased expression of HSP72 in RGCs at 3 and 7 days after GGA administration, but HSC70 was unchanged. After 5 weeks of IOP elevation, there was 27% +/- 6% loss of RGCs. The administration of GGA significantly reduced the loss of RGCs, lessened optic nerve damage, decreased the number of TUNEL-positive cells in the RGC layer, and increased HSP72. Quercetin administration abolished these protective effects. CONCLUSIONS: These results demonstrate that systemic administration of GGA protects RGCs from glaucomatous damage in a rat model and suggest a novel pathway for netroprotection for patients with glaucoma. PMID:14971562

  10. Laser sclerectomy and 5-FU controlled-drug-release biodegradable implant for glaucoma therapy

    NASA Astrophysics Data System (ADS)

    Villain, Franck L.; Parel, Jean-Marie A.; Kiss, Katalin; Parrish, Richard K.; Kuhne, Francois; Takesue, Yoshiko; Hostyn, Patrick

    1993-06-01

    Laser sclerectomy, a simple filtering procedure performed to alleviate high intraocular pressure in glaucoma patients, was taught to offer longer lasting effect and therefore improve the patient's outcome when compared with the standard trabeculectomy procedure. Recent clinical trials have shown that this was not the case and pharmacologic wound healing modulation is also required with this new procedure. Five-Fluorouracil (5-FU) is useful as an adjunct treatment for glaucoma filtering surgery. However, efficacy depends upon maintaining sustained drug levels, currently achieved by repeated daily injection of the drug for several weeks. To overcome this limitation, we designed a biodegradable implant for the sustained release of 5-FU. After laser sclerectomy, the implant is inserted through the same 1 mm wide conjunctival snip incision and positioned below the open channel. Implantation takes less than a minute. The implant releases the drug for over 15 days and totally biodegrades in less than 100 days. The combined laser surgery and implantation procedure show great potentials for the treatment of glaucoma.

  11. Glaucoma-inducing Procedure in an In Vivo Rat Model and Whole-mount Retina Preparation.

    PubMed

    Gossman, Cynthia A; Linn, David M; Linn, Cindy

    2016-01-01

    Glaucoma is a disease of the central nervous system affecting retinal ganglion cells (RGCs). RGC axons making up the optic nerve carry visual input to the brain for visual perception. Damage to RGCs and their axons leads to vision loss and/or blindness. Although the specific cause of glaucoma is unknown, the primary risk factor for the disease is an elevated intraocular pressure. Glaucoma-inducing procedures in animal models are a valuable tool to researchers studying the mechanism of RGC death. Such information can lead to the development of effective neuroprotective treatments that could aid in the prevention of vision loss. The protocol in this paper describes a method of inducing glaucoma - like conditions in an in vivo rat model where 50 µl of 2 M hypertonic saline is injected into the episcleral venous plexus. Blanching of the vessels indicates successful injection. This procedure causes loss of RGCs to simulate glaucoma. One month following injection, animals are sacrificed and eyes are removed. Next, the cornea, lens, and vitreous are removed to make an eyecup. The retina is then peeled from the back of the eye and pinned onto sylgard dishes using cactus needles. At this point, neurons in the retina can be stained for analysis. Results from this lab show that approximately 25% of RGCs are lost within one month of the procedure when compared to internal controls. This procedure allows for quantitative analysis of retinal ganglion cell death in an in vivo rat glaucoma model. PMID:27023167

  12. Glaucoma-inducing Procedure in an In Vivo Rat Model and Whole-mount Retina Preparation.

    PubMed

    Gossman, Cynthia A; Linn, David M; Linn, Cindy

    2016-01-01

    Glaucoma is a disease of the central nervous system affecting retinal ganglion cells (RGCs). RGC axons making up the optic nerve carry visual input to the brain for visual perception. Damage to RGCs and their axons leads to vision loss and/or blindness. Although the specific cause of glaucoma is unknown, the primary risk factor for the disease is an elevated intraocular pressure. Glaucoma-inducing procedures in animal models are a valuable tool to researchers studying the mechanism of RGC death. Such information can lead to the development of effective neuroprotective treatments that could aid in the prevention of vision loss. The protocol in this paper describes a method of inducing glaucoma - like conditions in an in vivo rat model where 50 µl of 2 M hypertonic saline is injected into the episcleral venous plexus. Blanching of the vessels indicates successful injection. This procedure causes loss of RGCs to simulate glaucoma. One month following injection, animals are sacrificed and eyes are removed. Next, the cornea, lens, and vitreous are removed to make an eyecup. The retina is then peeled from the back of the eye and pinned onto sylgard dishes using cactus needles. At this point, neurons in the retina can be stained for analysis. Results from this lab show that approximately 25% of RGCs are lost within one month of the procedure when compared to internal controls. This procedure allows for quantitative analysis of retinal ganglion cell death in an in vivo rat glaucoma model.

  13. Question on clinical efficiency and principles of diode laser radiation activity at a primary open-angle glaucoma

    NASA Astrophysics Data System (ADS)

    Bolshunov, A. V.; Litvinova, G. G.; Ilyina, O. S.; Easakiva, A. L.; Fyodorov, A. A.; Poleva, R. P.

    1999-07-01

    The efficiency of a diode laser with a wavelength 0,81 microns in treatment of an open-angle glaucoma is investigated. The diode LTP is a pathogenesis oriented method of treatment of an open angle glaucoma: it gives in improvement of outflow of an intraocular fluid, stabilization and improvement of visual functions for patients with initial and developed stages of disease at term of observation up to 12 months.

  14. Controlled five-year follow-up study of laser trabeculoplasty as primary therapy for open-angle glaucoma

    SciTech Connect

    Tuulonen, A.; Niva, A.K.; Alanko, H.I.

    1987-10-15

    We followed up 32 eyes of 32 patients with early glaucoma (22 with capsular glaucoma and ten with simple glaucoma) who received laser trabeculoplasty as a primary therapy. These eyes were compared with a matched control group of 32 eyes treated with medication initially. The success rate (intraocular pressure below 22 mm Hg with laser alone or medication alone) at five years was 50% (16 of 32 eyes) in the laser-treated group and 22% (seven of 32 eyes) in the control group (P less than .02). The control group required more modifications of their therapy to control intraocular pressure. The neuroretinal rim area in the control eyes decreased 2.5 times as much as in the laser group (P = .017). Changes in the Friedmann visual fields did not differ significantly between the two groups.

  15. Trans-scleral diode laser cyclophotocoagulation for refractory glaucoma after high-risk penetrating keratoplasty.

    PubMed

    Rodríguez-García, Alejandro; González-González, Luis Alonso; Carlos Alvarez-Guzmán, J

    2016-06-01

    To analyze the intraocular pressure reduction, number of anti-glaucoma medications needed, and post-operative complications of trans-scleral diode laser cyclophotocoagulation (DCPC) in patients with high-risk penetrating keratoplasty (PKP) and secondary refractory glaucoma. Prospective interventional, longitudinal, non-comparative series of cases, including 16 eyes of 15 patient's post-PKP on maximal anti-glaucoma medical therapy with intraocular pressures above 22 mmHg. All patients received 18 shots, 360° peri-limbal (avoiding the long posterior ciliary nerves and arteries at 3 and 9 o'clock positions) of trans-scleral DCPC (2000 mW, time: 2.0 s/shot). There was a 55.5 % reduction (total of 14.0 mmHg) of the mean pre-operative IOP (31.5 mmHg) after the first diode laser application (p = 0.0020). Re-treatment was required in 31.2 % of eyes over a mean period of 10.7 months. In these five eyes, the mean pre-operative IOP was 40.4 mmHg, which decreased to 15.0 mmHg post-therapy, and a mean IOP reduction of 25.4 mmHg (p = 0.0218). There was a 51.0 % reduction in the mean number of medications used after the first, and a 57.1 % reduction after a second laser application. The incidence of failure (IOP ≥ 22 mmHg or need of additional medical therapy) from initial intervention to loss of follow-up was 1.3 % per person-month. DCPC effectively reduces the intraocular pressure and the number of anti-glaucoma medications with few complications in patients after high-risk PKP and secondary glaucoma. Only, one-third of the eyes needed a second intervention to control the intraocular pressure. Post-DCPC complications were limited to phthisis bulbi and endothelial dysfunction, one eye each. Please check and confirm the author names and initials are correct. Also, kindly confirm the details in the metadata are correct.

  16. MicroPulse Laser Trabeculoplasty for the Treatment of Open-Angle Glaucoma.

    PubMed

    Lee, Jacky W Y; Yau, Gordon S K; Yick, Doris W F; Yuen, Can Y F

    2015-12-01

    The aim of the study was to investigate the safety and efficacy of using MLT in the treatment of open-angle glaucoma (OAG).This prospective cohort included subjects ≥18 years of age with OAG, defined as the open angle on gonioscopy with glaucomatous optic neuropathy evident from optical coherence tomography. Subjects with IOP < 21 mm Hg were classified as normal tension glaucoma and those with IOP ≥21 mm Hg were classified as primary open-angle glaucoma. Those with angle closure, secondary glaucoma, prior laser trabeculoplasty, use of systemic IOP-lowering medications, corneal pathologies, follow-up <6 months, recent intraocular surgery, or only 1 functional eye were excluded. A single session of unilateral MLT treatment was delivered using a 577 nm diode laser to 360° of the trabecular meshwork to reduce IOP or medication load. Medications were titrated up or down at 1 month after laser to achieve a 25% IOP reduction from presentation or an IOP <18 mm Hg, whichever was lower. The following were compared using the Repeated Measures ANOVA with Bonferroni's Multiple Comparison Test: IOP (on presentation, pre-MLT, day 1, 1 week, 1 month, 3 months, and 6 months after MLT) and the number of medications (pre-MLT, 3 months, and 6 months after MLT). After 6 months, responders with initial success to MLT (IOP reduction ≥20% at 1 month) received treatment in the fellow eye.In 48 subjects with OAG, the mean number of MLT shots applied was 120.5 ± 2.0 shots using a mean energy of 1000 mW per shot. Only 7.5% had a mild, self-limiting anterior uveitis postlaser with no change in the Snellen visual acuity at 6 months (P's > 0.5). The IOP and number of medications were significantly reduced at all time intervals following MLT compared to the pre-MLT level (P's < 0.0001). At 6 months, the IOP was reduced by 19.5% in addition to a 21.4% reduction in medication compared to pretreatment levels. The MLT success rate was 72.9%. During the first 6 months

  17. Transscleral photodisruption for the treatment of glaucoma

    NASA Astrophysics Data System (ADS)

    Sacks, Zachary S.; Loesel, Frieder H.; Durfee, Charles G., III; Kurtz, Ron M.; Juhasz, Tibor; Mourou, Gerard A.

    1999-03-01

    To evaluate transscleral glaucoma surgery techniques using ultrashort pulsed lasers, we attempted to produce photodisruption on the inner surface of the sclera without damaging the overlying tissue. We identified two methods, using pulses centered at 1700 nm and a transparency inducing drug, to produce the spatial and temporal confinement of the pulse necessary to produce photodisruption in the highly scattering sclera. When fully developed these concepts may help address the longstanding limitations of current glaucoma surgical techniques.

  18. Selective laser trabeculoplasty in treating post-trabeculectomy advanced primary open-angle glaucoma

    PubMed Central

    ZHANG, HONGYANG; YANG, YANGFAN; XU, JIANGANG; YU, MINBIN

    2016-01-01

    The aim of this study was to investigate the safety and efficacy of selective laser trabeculoplasty (SLT) treatment of patients with primary open-angle glaucoma (POAG) who could not obtain target intraocular pressure (IOP) through post-trabeculectomy medication. Sixteen patients with POAG (18 eyes), who could not obtain target IOP following medication and surgery, were treated with 360° SLT. The IOP, anterior chamber inflammation, and daytime and long-term IOP fluctuations before and 2 h, 1 day, 7 days, 1 month, 3 months, 6 months and 9 months after SLT were documented. SLT treatment success was defined as >20% IOP reduction compared with the baseline IOP at 6 and 9 months after the laser treatment date. Prior to SLT, the patients were administered different types (average, 2.8±0.8) of anti-glaucoma drugs and had an average IOP of 21.3±3.4 mmHg. Following SLT, the average IOP decreased to 16.2±3.0 mmHg and the success rate was 77.7%. The pre-SLT daytime IOP fluctuation was 4.1±1.4 mmHg, which decreased to 2.6±1.1 mmHg following the laser treatment (P<0.05). In conclusion, this study demonstrated that SLT could reduce the IOP in post-trabeculectomy patients with POAG, and reduce the daytime IOP fluctuations. PMID:26998042

  19. A review of drug-induced acute angle closure glaucoma for non-ophthalmologists

    PubMed Central

    Ah-kee, Elliott Yann; Egong, Eric; Shafi, Ahad; Lim, Lik Thai; Yim, James Li

    2015-01-01

    Acute angle closure glaucoma is an ophthalmic emergency and can lead to blindness if left untreated. Several types of drugs have the potential to precipitate acute angle closure glaucoma. These include adrenergic, cholinergic and anticholinergic, antidepressants, anticoagulants and sulfa-based agents. This article provides a basic overview of the risk factors and pathophysiologic mechanisms involved in angle closure glaucoma and focuses on drug-induced angle closure glaucoma for the non-ophthalmologist. A PubMed search limited to the English language was conducted to find relevant literature for the purpose of this article. Most attacks occur in subjects unaware that they are at risk due to innately narrow iridocorneal angles. Clinicians should always review medications in patients presenting with symptoms of acute angle closure glaucoma. The aim of this article is to bring this ophthalmic condition to the attention of clinicians, particularly those outside the field of ophthalmology who commonly prescribe these medications or see these patients prior to referring to ophthalmologists. PMID:26535174

  20. A review of drug-induced acute angle closure glaucoma for non-ophthalmologists.

    PubMed

    Ah-Kee, Elliott Yann; Egong, Eric; Shafi, Ahad; Lim, Lik Thai; Yim, James Li

    2015-01-01

    Acute angle closure glaucoma is an ophthalmic emergency and can lead to blindness if left untreated. Several types of drugs have the potential to precipitate acute angle closure glaucoma. These include adrenergic, cholinergic and anticholinergic, antidepressants, anticoagulants and sulfa-based agents. This article provides a basic overview of the risk factors and pathophysiologic mechanisms involved in angle closure glaucoma and focuses on drug-induced angle closure glaucoma for the non-ophthalmologist. A PubMed search limited to the English language was conducted to find relevant literature for the purpose of this article. Most attacks occur in subjects unaware that they are at risk due to innately narrow iridocorneal angles. Clinicians should always review medications in patients presenting with symptoms of acute angle closure glaucoma. The aim of this article is to bring this ophthalmic condition to the attention of clinicians, particularly those outside the field of ophthalmology who commonly prescribe these medications or see these patients prior to referring to ophthalmologists.

  1. Guiding glaucoma laser surgery using Fourier-domain optical coherence tomography at 1.3 μm

    NASA Astrophysics Data System (ADS)

    Bayleyegn, Masreshaw D.; Makhlouf, Houssine; Crotti, Caroline; Plamann, Karsten; Dubois, Arnaud

    2012-06-01

    Glaucoma is a disease of the optic nerve that is usually associated with an increased internal pressure of the eye and can lead to a decreased vision and eventually blindness. It is the second leading cause of blindness worldwide with more than 80 million people affected and approximately 6 million blind. The standard clinical treatment for glaucoma, after unsuccessful administration of eyedrops and other treatments, is performing incisional surgery. However, due to post-surgical complications like scarring and wound healing, this conventional method has a global success rate of only about 60%. In comparison, as femtosecond laser surgery may be performed in volume and is a priori less invasive and less susceptible of causing scarring, glaucoma laser surgery could be a novel technique to supplement the conventional glaucoma surgery. We have been working on the development of a new tool for glaucoma treatment that uses an optimized femtosecond laser source centered at 1.65 μm wavelength for making the surgery and an imaging system based on optical coherence tomography (OCT) for guiding the laser surgery. In this proceeding, we present the results obtained so far on the development and utilization of Fourier-domain OCT imaging system working at 1.3 μm center wavelength for guiding the laser incision. Cross-sectional OCT image of pathological human cornea showing the Schlemm's canal, where the surgery is intended to be done, is presented. By coupling OCT imaging system with the laser incision system, we also demonstrate real-time imaging of femtosecond laser incision of cornea.

  2. Correlation between Lamina Cribrosa Tilt Angles, Myopia and Glaucoma Using OCT with a Wide Bandwidth Femtosecond Mode-Locked Laser

    PubMed Central

    Shoji, Takuhei; Kuroda, Hiroto; Suzuki, Masayuki; Baba, Motoyoshi; Hangai, Masanori; Araie, Makoto; Yoneya, Shin

    2014-01-01

    Purpose To measure horizontal and vertical lamina cribrosa (LC) tilt angles and investigate associated factors using prototype optical coherence tomography (OCT) with a broad wavelength laser light source. Design Cross sectional study. Methods Twenty-eight no glaucoma eyes (from 15 subjects) and 25 glaucoma eyes (from 14 patients) were enrolled. A total of 300 optic nerve head B-scans were obtained in 10 µm steps and the inner edge of Bruch's membrane opening (BMO) was identified as the reference plane. The vertical and horizontal angles between BMO line and approximate the best-fitting line for the surface of the LC were measured and potential associated factors were estimated with univariate and multivariate logistic regression analyses. Results The median (interquartile range) horizontal and vertical tilt angles were 7.10 (2.43–11.45) degrees and 4.15 (2.60–6.85) degrees in eyes without glaucoma and 8.50 (4.40–14.10) degrees and 9.30 (6.90–14.15) degrees in glaucoma eyes, respectively. The refractive errors had a statistically significant association with horizontal LC tilt angles (coefficients, −1.53 per diopter) and glaucoma had a significant correlation with vertical tilt angles (coefficients, 6.56) using multiple logistic regression analysis (p<0.001). Conclusions OCT allowed evaluation of the internal tilting of the LC compared with the BMO. The horizontal internal LC tilt angle was correlated with refractive errors, corresponding to myopic physiological changes, and vertical internal LC tilt was correlated with glaucoma, corresponding to glaucomatous pathological changes. These parameters have important implications for investigation of the correlation between myopia, glaucoma and LC morphological features. PMID:25551632

  3. A Magnetic Microbead Occlusion Model to Induce Ocular Hypertension-Dependent Glaucoma in Mice

    PubMed Central

    Cueva Vargas, Jorge L.; Di Polo, Adriana

    2016-01-01

    The use of rodent models of glaucoma has been essential to understand the molecular mechanisms that underlie the pathophysiology of this multifactorial neurodegenerative disease. With the advent of numerous transgenic mouse lines, there is increasing interest in inducible murine models of ocular hypertension. Here, we present an occlusion model of glaucoma based on the injection of magnetic microbeads into the anterior chamber of the eye using a modified microneedle with a facetted bevel. The magnetic microbeads are attracted to the iridocorneal angle using a handheld magnet to block the drainage of aqueous humour from the anterior chamber. This disruption in aqueous dynamics results in a steady elevation of intraocular pressure, which subsequently leads to the loss of retinal ganglion cells, as observed in human glaucoma patients. The microbead occlusion model presented in this manuscript is simple compared to other inducible models of glaucoma and also highly effective and reproducible. Importantly, the modifications presented here minimize common issues that often arise in occlusion models. First, the use of a bevelled glass microneedle prevents backflow of microbeads and ensures that minimal damage occurs to the cornea during the injection, thus reducing injury-related effects. Second, the use of magnetic microbeads ensures the ability to attract most beads to the iridocorneal angle, effectively reducing the number of beads floating in the anterior chamber avoiding contact with other structures (e.g., iris, lens). Lastly, the use of a handheld magnet allows flexibility when handling the small mouse eye to efficiently direct the magnetic microbeads and ensure that there is little reflux of the microbeads from the eye when the microneedle is withdrawn. In summary, the microbead occlusion mouse model presented here is a powerful investigative tool to study neurodegenerative changes that occur during the onset and progression of glaucoma. PMID:27077732

  4. 193 nm excimer laser sclerostomy in pseudophakic patients with advanced open angle glaucoma.

    PubMed Central

    Allan, B D; van Saarloos, P P; Cooper, R L; Constable, I J

    1994-01-01

    A modified open mask system incorporating an en face air jet to dry the target area during ablation and a conjunctival plication mechanism, which allows ab externo delivery of the 193 nm excimer laser without prior conjunctival dissection, has been developed to form small bore sclerostomies accurately and atraumatically. Full thickness sclerostomies, and sclerostomies guarded by a smaller internal ostium can be created. A pilot therapeutic trial was conducted in pseudophakic patients with advanced open angle glaucoma. Six full thickness sclerostomies (200 microns and 400 microns diameter) and three guarded sclerostomies were created in nine patients by 193 nm excimer laser ablation (fluence per pulse 400 mJ/cm2, pulse rate 16 Hz, air jet pressure intraocular pressure +25 mm Hg). After 6 months' follow up, intraocular pressure was controlled (< or = 16 mm Hg) in eight of the nine patients (6/9 without medication). Early postoperative complications included hyphaema (trace--2.5 mm) (6/9), temporary fibrinous sclerostomy occlusion (4/9), profound early hypotony (all patients without fibrinous occlusion), and suprachoroidal haemorrhage in one case. Conjunctival laser wounds were self sealing. Small bore laser sclerostomy procedures are functionally equivalent to conventional full thickness procedures, producing early postoperative hypotony, with an increased risk of suprachoroidal haemorrhage in association with this. Further research is required to improve control over internal guarding in excimer laser sclerostomy before clinical trials of this technique can safely proceed. Images PMID:8148335

  5. Incidence, severity and factors related to drug-induced keratoepitheliopathy with glaucoma medications

    PubMed Central

    Fukuchi, Takeo; Wakai, Kimiko; Suda, Kieko; Nakatsue, Tomoko; Sawada, Hideko; Hara, Hiroaki; Ueda, Jun; Tanaka, Takayuki; Yamada, Akiko; Abe, Haruki

    2010-01-01

    Purpose To evaluate the incidence, severity, and factors related to drug-induced keratoepitheliopathy in eyes using antiglaucoma eye drops. Patients and methods In a cross-sectional study, 749 eyes from 427 patients who had used one or more antiglaucoma eye drops were examined at Niigata University Medical and Dental Hospital or related facilities. The incidence and severity of superficial punctate keratitis (SPK), patient gender and age, type of glaucoma, and type of eye drops were recorded. SPK was graded according to the AD (A, area; D, density) classification. The severity score (SS) was calculated from A × D. Results SPK was observed in 382 (51.0%) of 749 eyes that had received any type of antiglaucoma eye drops. While 254 eyes (33.9%) were classified as A1D1 (SS 1), 34 eyes (4.6%) had severe SPK with SS 4 or more. The number of eye drops and the total dosing frequency per day were significantly greater in SPK-positive eyes than in eyes without SPK. The number of eye drops was proportional to the frequency and severity of SPK. Among eyes that were treated with three or more eye drops, SPK was more severe and more frequent in older patients (≥71 years). In addition, a considerable difference was detected for each type of glaucoma. Conclusion Drug-induced keratoepitheliopathy is often observed in eyes that have received recent antiglaucoma eye drops. The number of eye drops, the total dose frequency per day, patient age, and type of glaucoma may affect this condition. We have to consider not only the effects on intraocular pressure but also the incidence and severity of drug-induced keratoepitheliopathy as a frequent side effect of glaucoma medications. PMID:20463785

  6. Experimental glaucoma induced by ocular injection of magnetic microspheres.

    PubMed

    Bunker, Shannon; Holeniewska, Joanna; Vijay, Sauparnika; Dahlmann-Noor, Annegret; Khaw, Peng; Ng, Yin-Shan; Shima, David; Foxton, Richard

    2015-01-01

    Progress in understanding the pathophysiology, and providing novel treatments for glaucoma is dependent on good animal models of the disease. We present here a protocol for elevating intraocular pressure (IOP) in the rat, by injecting magnetic microspheres into the anterior chamber of the eye. The use of magnetic particles allows the user to manipulate the beads into the iridocorneal angle, thus providing a very effective blockade of fluid outflow from the trabecular meshwork. This leads to long-lasting IOP rises, and eventually neuronal death in the ganglion cell layer (GCL) as well as optic nerve pathology, as seen in patients with the disease. This method is simple to perform, as it does not require machinery, specialist surgical skills, or many hours of practice to perfect. Furthermore, the pressure elevations are very robust, and reinjection of the magnetic microspheres is not usually required unlike in some other models using plastic beads. Additionally, we believe this method is suitable for adaptation for the mouse eye.

  7. Corneal transplantation and glaucoma.

    PubMed

    Haddadin, Ramez I; Chodosh, James

    2014-01-01

    Glaucoma is the leading cause of irreversible vision loss post-keratoplasty and an important cause of graft failure. With newer techniques, such as lamellar, endothelial, and laser-assisted keratoplasty as well as keratoprosthesis gaining popularity, clinicians will need to consider the incidence, risks, evaluation, and management of glaucoma for each type of keratoplasty when determining which type of transplant may be most appropriate. A comprehensive literature search of glaucoma in the setting of corneal transplantation was performed and serves as the basis for this review. Preexisting glaucoma and aphakia are notable risk factors. Patients that are candidates for deep anterior lamellar keratoplasty may benefit from reduced rates of post-keratoplasty glaucoma. Although glaucoma also complicates eyes with Descemet stripping endothelial keratoplasty, the severity is less and the intraocular pressure is more easily controlled when compared to penetrating keratoplasty. Endothelial keratoplasty creates unique perioperative issues mostly related to management of anterior chamber air bubbles.

  8. Selective laser trabeculoplasty (SLT) vs other treatment modalities for glaucoma: systematic review

    PubMed Central

    McAlinden, C

    2014-01-01

    Purpose Systemic review to compare selective laser trabeculoplasty (SLT) to other glaucoma treatment options in terms of their intraocular pressure (IOP)-lowering effect. Methods Searches of the following databases were performed: PubMed, Cochrane Central Register of Controlled Trials, Ovid, EMBASE, metaRegister of Controlled Trials, and ClinicalTrials.gov. Only randomised controlled trials (RCTs) published in peer-reviewed journals comparing SLT to other glaucoma treatment options were considered. The main outcome measure was the change in IOP from baseline. Results An initial search of PubMed identified 23 RCTs with 17 meeting the inclusion criteria. Nine RCTs compared 180° SLT to 180° argon laser trabeculoplasty (ALT) and one trial compared 360° SLT to 360° ALT, all reporting no difference in terms of IOP reduction from baseline. One RCT reported better outcomes with SLT at 1 year but this effect regressed at 2 years. Three trials compared 360° SLT to medical therapy and found no difference between the two treatment options. One trial found greater IOP reduction with latanoprost vs 90° and 180° SLT, and greater IOP reduction with 180° and 360° SLT versus 90° SLT, however no differences were found between 360° SLT versus latanoprost or 360° vs 180° SLT. Two trials compared 180° SLT to 360° SLT finding no difference in IOP reduction. Two trials compared 180° SLT to 90° SLT, one finding no significant difference and one finding greater IOP reduction with 180° SLT over 90° SLT. One trial compared excimer laser trabeculotomy (ELT) to 180° SLT, finding no differences in IOP reduction up to 3 months follow-up but greater IOP reduction with ELT at time intervals between 9 and 24 months. There were no RCTs identified that compared SLT to surgery. Conclusion In terms of the IOP lowering effect, there is no difference between SLT and ALT. Three trials indicate no difference between 360° SLT and medical therapy, with one of the trials indicating greater

  9. Selective laser trabeculoplasty for primary open angle glaucoma: six-year follow up

    NASA Astrophysics Data System (ADS)

    Koev, Krassimir

    2005-04-01

    In order to establish the long-term efficacy of selective laser trabeculoplasty for primary open-angle glaucoma [POAG], trabecular meshwork of 34 eyes (21 patients) with POAG was treated with Q-switched frequency doubled Nd-YAG laser with wavelength of 532 nm Coherent Selecta 7000 (SLT). The eyes were divided in two groups: group 1-18 eyes with pigmentation degree in the frontal chamber angle of 1 and 2; group 2-16 eyes with pigmentation degree of 3 and 4. An average of 104 spots on 360 degrees was applied stepwise to the trabecular meshwork of every eye. The treatment and follow up period lasted 6 years. The mean prepoerative intraocular pressure [IOP] in group 1 was 25,5+/-1,5 mmHg, and in group 2-26+/-1 mmHg. During the last visit 6 years after SLT, the mean IOP in group 1 was 18,7+/-1.4 mmHg. Statistically significant decrease of IOP [p<0.001] was observed after SLT by an average of 6,8 mmHg [26.7%]. During the last visit 6 years after SLT in group 2, the mean IOP was 18.8+/-1.2 mmHg. Statistically significant IOP decrase method for POAG treatment and that IOP decrase in treated eyes is preserved for several years.

  10. Laser induced nuclear reactions

    SciTech Connect

    Ledingham, Ken; McCanny, Tom; Graham, Paul; Fang Xiao; Singhal, Ravi; Magill, Joe; Creswell, Alan; Sanderson, David; Allott, Ric; Neely, David; Norreys, Peter; Santala, Marko; Zepf, Matthew; Watts, Ian; Clark, Eugene; Krushelnick, Karl; Tatarakis, Michael; Dangor, Bucker; Machecek, Antonin; Wark, Justin

    1998-12-16

    Dramatic improvements in laser technology since 1984 have revolutionised high power laser technology. Application of chirped-pulse amplification techniques has resulted in laser intensities in excess of 10{sup 19} W/cm{sup 2}. In the mid to late eighties, C. K. Rhodes and K. Boyer discussed the possibility of shining laser light of this intensity onto solid surfaces and to cause nuclear transitions. In particular, irradiation of a uranium target could induce electro- and photofission in the focal region of the laser. In this paper it is shown that {mu}Ci of {sup 62}Cu can be generated via the ({gamma},n) reaction by a laser with an intensity of about 10{sup 19} Wcm{sup -2}.

  11. Peripapillary Retinal Nerve Fiber Layer Assessment of Spectral Domain Optical Coherence Tomography and Scanning Laser Polarimetry to Diagnose Preperimetric Glaucoma

    PubMed Central

    Rao, Harsha L.; Yadav, Ravi K.; Addepalli, Uday K.; Chaudhary, Shashikant; Senthil, Sirisha; Choudhari, Nikhil S.; Garudadri, Chandra S.

    2014-01-01

    Purpose To compare the abilities of peripapillary retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting preperimetric glaucoma. Methods In a cross-sectional study, 35 preperimetric glaucoma eyes (32 subjects) and 94 control eyes (74 subjects) underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate preperimetric glaucoma eyes from control eyes was compared using area under receiver operating characteristic curves (AUC), sensitivities at fixed specificities and likelihood ratios (LR). Results AUC of the global average RNFL thickness of SDOCT (0.786) was significantly greater (p<0.001) than that of GDx ECC (0.627). Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of the inferior, superior and temporal quadrant RNFL thickness parameters of SDOCT were also significantly (p<0.05) greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0. Conclusions Abilities of the RNFL parameters of SDOCT and GDx ECC to diagnose preperimetric glaucoma were only moderate. Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma. PMID:25279801

  12. [Glaucoma and retinal surgery].

    PubMed

    Müller, M; Geerling, G; Zierhut, M; Klink, T

    2010-05-01

    In the therapeutic approach to complex glaucomas different initial situations were considered: pre-existing glaucoma, induction of glaucoma after vitreoretinal surgery and antiglaucomatous procedures. In pre-existing glaucoma and after filtering surgery maintenance of the filtering bleb requires a vitreoretinal approach for conjunctiva preservation with techniques such as pneumatic retinopexy or small gauge vitrectomy. After vitreoretinal surgery an increase in intraocular pressure (IOP) is common. Secondary glaucoma may occur after scleral buckling and after vitrectomy with or without gas or silicone oil tamponade as well as after application of steroids. Angle closure glaucoma after scleral buckling develops because of congestion and anterior rotation of the ciliary body. Vitreous tamponades with expansive or saturated gases may cause angle-closure glaucoma with or without pupillary blockage and may critically shorten ocular perfusion. Postoperative checks, immediate action and a ban on boarding aircraft over the period of intraocular gas tamponade prevent permanent damage to the eye. The majority of secondary glaucomas can effectively be controlled by topical medication and adequate postoperative posture of the patient. Besides the temporary use of systemic antiglaucomatous medication or laser therapy, very rarely in cases of massive swelling or overfill, a direct intervention, such as partial gas or silicone oil removal is required. A prophylactic inferior peripheral iridectomy prevents pupillary blockage in aphakic eyes with intraocular tamponade. In cases of heavy silicone oil use, the peripheral iridectomy is placed in the superior position. Nd:YAG laser application will regulate IOP in cases of occlusion. Secondary glaucoma due to silicone oil emulsification overload is treated by trabecular meshwork aspiration and lavage. In refractory glaucoma repetitive cyclophotocoagulation and drainage implants represent an approved method for long-term IOP regulation

  13. Laser-induced bioluminescence

    SciTech Connect

    Hickman, G.D.; Lynch, R.V. III

    1981-01-01

    A project has been initiated to determine the feasibility of developing a complete airborne remote sensing system for rapidly mapping high concentration patches of bioluminescent organisms in the world's oceans. Conceptually, this system would be composed of a laser illuminator to induce bioluminescence and a low light level image intensifier for detection of light. Initial laboratory measurements consisted of using a 2-J flash lamp pulsed optical dye laser to excite bioluminescence in the marine dinoflagellate Pyrocustis lunula at ambient temperature using Rhodamine 6G as the lasing dye (585 nm) and a laser pulse width of 1 microsec. After a latency period of 15-20 msec, the bioluminescence maximum occurred in the blue (480 nm is the wavelength maximum for most dinoflagellate bioluminescence) with the peaking occurring approximately 65 msec after the laser pulse. Planned experiments will investigate the effect of different excitation wavelengths and energies at various temperatures and salinities of the cultures.

  14. Conjunctival modifications induced by medical and surgical therapies in patients with glaucoma.

    PubMed

    Mastropasqua, Leonardo; Agnifili, Luca; Mastropasqua, Rodolfo; Fasanella, Vincenzo

    2013-02-01

    Lowering intra-ocular pressure, either medically or surgically, is the proven strategy to control glaucoma, though profound changes to the ocular surface and conjunctiva are caused. Toxicity and allergy initiated by medical therapy induce modifications, which progressively worsen with the length of treatment and number of drugs. Conjunctival changes lead to symptoms of ocular surface disease, reduced quality of life, reduced therapeutic compliance and increased risk of surgical failure. Surgery modifies conjunctiva by inducing bleb formation in fistulizing techniques, and by activating secondary aqueous humour outflow pathways, such as trans-scleral routes, in both filtration and bleb-less approaches. The use of unpreserved medications, limitation of intra-operative conjunctival damage and development of bleb-less surgery are advisable.

  15. Nanotechnology Applications for Glaucoma.

    PubMed

    Cetinel, Sibel; Montemagno, Carlo

    2016-01-01

    Glaucoma is the second leading cause of blindness worldwide, and the antiglaucoma treatments currently available suffer from various complications. Nanotechnology-based treatments show a great deal of promise in overcoming these complications and form the basis for next-generation glaucoma treatment strategies, with the help of applications such as controlled release, targeted delivery, increased bioavailability, diffusion limitations, and biocompatibility. Significant progress has been made in nanomedicine in the efficiency of antiglaucoma medications, nanofabrication systems such as microelectromechanical systems that remove the limitations of nanodevices, and tissue regeneration vesicles for developing glaucoma treatments not based on intraocular pressure. With the use of these advanced technologies, the prevention of glaucoma-induced blindness will be possible in the near future. Herein, we reviewed the recent advances in nanotechnology-based treatment strategies for glaucoma.

  16. Nanotechnology Applications for Glaucoma.

    PubMed

    Cetinel, Sibel; Montemagno, Carlo

    2016-01-01

    Glaucoma is the second leading cause of blindness worldwide, and the antiglaucoma treatments currently available suffer from various complications. Nanotechnology-based treatments show a great deal of promise in overcoming these complications and form the basis for next-generation glaucoma treatment strategies, with the help of applications such as controlled release, targeted delivery, increased bioavailability, diffusion limitations, and biocompatibility. Significant progress has been made in nanomedicine in the efficiency of antiglaucoma medications, nanofabrication systems such as microelectromechanical systems that remove the limitations of nanodevices, and tissue regeneration vesicles for developing glaucoma treatments not based on intraocular pressure. With the use of these advanced technologies, the prevention of glaucoma-induced blindness will be possible in the near future. Herein, we reviewed the recent advances in nanotechnology-based treatment strategies for glaucoma. PMID:26693592

  17. One Year of Glaucoma Research in Review: 2012 to 2013

    PubMed Central

    Kim, Charles; Demetriades, Anna M.; Radcliffe, Nathan M.

    2014-01-01

    Purpose The objective of this study was to provide the practicing clinical ophthalmologist with an update of pertinent glaucoma literature published from 2012 to 2013. Design Literature review. Methods The authors conducted a 1-year (July 1, 2012, to September 30, 2013) English-language glaucoma literature search on PubMed using the following terms: glaucoma, automated perimetry, optic nerve imaging, optical coherence tomography, glaucoma structure and function, intraocular pressure, central corneal thickness, glaucoma medical therapy, neuroprotection, glaucoma laser treatment, secondary glaucoma, glaucoma surgery, and miscellaneous topics in glaucoma. Results Of 2659 articles on glaucoma published during our time frame, this review selected original and review articles that reflect novel aspects and updates in the field of glaucoma, while excluding letters to the editor, unpublished works, and abstracts. Preference was given to human research. Conclusions This review focuses on literature that is applicable to ophthalmologists in practice and also highlights studies that may enhance the diagnosis and management of glaucoma. PMID:25177529

  18. Glaucoma (image)

    MedlinePlus

    Glaucoma is a condition of increased fluid pressure inside the eye. The increased pressure causes compression of ... nerve which can eventually lead to nerve damage. Glaucoma can cause partial vision loss, with blindness as ...

  19. Selective laser trabeculoplasty compared with medical treatment for the initial management of open angle glaucoma or ocular hypertension.

    PubMed

    Pérez, Efraín; Rada, Gabriel; Maul, Eugenio

    2015-12-16

    Selective laser trabeculoplasty is a relatively new therapeutic alternative for the management of open angle glaucoma and ocular hypertension. On the other hand, medical treatment has robust data supporting its efficacy and has progressed in last decades with the introduction of prostaglandin analogues. To compare these two therapies, we searched Epistemonikos database, which is maintained by screening 30 databases, and identified four systematic reviews including four randomized and one non-randomized clinical trial. We combined the evidence using meta-analysis and generated a summary of findings table following the GRADE approach. We concluded that selective laser trabeculoplasty leads to a smaller absolute intraocular pressure reduction than medical treatment. However, it is not clear if there are differences in treatment success rate or need of additional antiglaucomatous interventions, because the quality of the evidence is low.

  20. Selective laser trabeculoplasty compared with medical treatment for the initial management of open angle glaucoma or ocular hypertension.

    PubMed

    Pérez, Efraín; Rada, Gabriel; Maul, Eugenio

    2015-01-01

    Selective laser trabeculoplasty is a relatively new therapeutic alternative for the management of open angle glaucoma and ocular hypertension. On the other hand, medical treatment has robust data supporting its efficacy and has progressed in last decades with the introduction of prostaglandin analogues. To compare these two therapies, we searched Epistemonikos database, which is maintained by screening 30 databases, and identified four systematic reviews including four randomized and one non-randomized clinical trial. We combined the evidence using meta-analysis and generated a summary of findings table following the GRADE approach. We concluded that selective laser trabeculoplasty leads to a smaller absolute intraocular pressure reduction than medical treatment. However, it is not clear if there are differences in treatment success rate or need of additional antiglaucomatous interventions, because the quality of the evidence is low. PMID:26730963

  1. [Angle-closure chronic glaucoma].

    PubMed

    Lachkar, Y

    2003-10-01

    The incidence of chronic angle closure glaucoma is considerably greater than the incidence of the acute type. This type of glaucoma may mimic primary open angle glaucoma with visual field deterioration, optic nerve alteration and intraocular pressure elevation with a quiet painless eye. Its diagnosis is based on indentation gonioscopy showing peripheral anterior synechiae. The mechanisms of angle closure are the pupillary block, the plateau iris configuration and the creeping form. The treatment of chronic angle closure glaucoma is based on laser peripheral iridotomy. PMID:14646832

  2. Salvia miltiorrhiza extracts protect against retinal injury in a rat glaucoma model.

    PubMed

    Zhu, Qi; Su, Guanfang; Nie, Lili; Wang, Chenguang; He, Yuxi; Liu, Xin

    2014-06-01

    Glaucoma is a serious progressive degenerative disorder of the eye that leads to the continuous loss of retinal ganglion cells. Traditional Chinese medicine provides an important source for new drug screening and identification. The present study used Salvia miltiorrhiza (Danshen) extracts to examine the potential neuroprotective effects for the eye in a rat model of experimental glaucoma. The results of the study indicated that Salvia miltiorrhiza extracts were unable to prevent intraocular pressure increase in the laser-induced glaucoma model, but the treatment did reduce cell loss during glaucoma progression. Therefore, the results provide the basis for the development of a novel therapeutic agent that exhibits neuroprotective effects against glaucoma. In the future, further studies are required to purify the extracts and determine the effective bioactive components of Salvia miltiorrhiza.

  3. [Glaucoma and corneal transplantation].

    PubMed

    Geerling, G; Müller, M; Zierhut, M; Klink, T

    2010-05-01

    Glaucoma and corneal disorders are often associated and are of diagnostic, therapeutic and prognostic relevance for each other. Glaucoma is already present in approximately 15% of eyes prior to keratoplasty, whereas in addition approximately 15% of cases are diagnosed following corneal transplantation. Corneal opacities, surface irregularities and pachymetric deviations from the norm can have a negative impact on tonometry, perimetry and morphological glaucoma diagnosis. Digital and intracameral tonometry as well as flash VEP to determine the visual potential can be helpful in this setting. Increased intraocular pressure (IOP), long-term application of antiglaucomatous medication or the use of antimetabolites in glaucoma surgery can all induce keratopathy. Therefore, intraocular pressure should be regulated prior to corneal transplantation. Risk factors for the evolution of glaucoma following corneal transplantation are the specific indication and surgical technique (e. g. combined corneal and cataract/vitreoretinal surgery), as well as postoperative steroid application and chamber angle synechiae. Unpreserved glaucoma medication without pro-inflammatory effects should be preferred following keratoplasty. In the long term surgery to control IOP is required in approximately 25% of eyes. The wider use of lamellar techniques for corneal transplantation is likely to reduce the incidence of secondary glaucoma.

  4. Laser Induced Thermal Keratoplasty

    NASA Astrophysics Data System (ADS)

    Householder, John; Horwitz, Larry S.; Lowe, Kenneth W.; Murrillo, Adolfo

    1989-09-01

    A technique of corneal surgery that is thermally induced and relatively nonenvasive has been studied by the authors, and the preliminary results of the thermal keratoplasty performed on live rabbits are reported here. A carbon dioxide laser was used with simple optical and pointing systems to thermally induce several arbitrary patterns of corneal reformation. Endothelial photographs were taken before the procedure and then again ten days after. They indicated no damage in the Descemet's membrane nor was there damage observed to the endothelium. As much, as 14 "diopters" of change occurred in the corneal keratometry with both positive and negative directions signs. The magnitude and direction of the change were recorded as functions of the pattern of the therapy produced and the laser energy deposited in the stroma. Any corneal reformation was tracked as a function of time subsequent to the procedure. A-minor decay was observed within the first three days of the procedure and the majority of the reformations have maintained at the time of this writing. Since radiation at this wavelength is highly attenuated and absorbed in cornea, no change was observed beyond mid-stroma and the lens and retina appeared uneffective. The authors believe that this technology will be a significant contributor to corneal refractive procedures in the near future. Unlike any refractive surgery currently practiced, this technology may lead to a procedure that: 1) is reversible, 2) is re.eatable, 3) stren thens rather then weakens the cornea, 4) is a..arentl more stable, 5) is more flexible in the types of corneal curvature changes it can produce, 6) results in very clean mires, 7) is painless, and 8) results in total corneal clarity.

  5. Management and Visual Outcome in Patients of Lens-induced Glaucomas at a Tertiary Eye Care Hospital in South India

    PubMed Central

    Vaibhav, K

    2016-01-01

    ABSTRACT Aims: To outline the different characteristics of glaucomas and to determine the risk factors and their consequences on postoperative visual acuity, intraocular pressure (IOP), and inflammation, including corneal changes and optic disk changes. Settings and designs: Longitudinal prospective study done over a period of 1.5 years in a medical college hospital. Materials and methods: Fifty patients of lens-induced glaucoma (LIG) were included. At presentation, visual acuity, IOP, and inflammation, including corneal changes, were recorded. After medical line of treatment, postoperatively patients were followed up regularly at 2 and 7 weeks interval and the same parameters were evaluated including optic disk changes. Statistical analysis used: Paired t-test, chi-square test wherever applicable with p-value < 0.05 as significant. Results: The mean age of presentation was 60.68 years with female to male ratio of 1.7:1. The best corrected visual acuity(BCVA) of 6/18 or more was found in 54% cases, whereas visual acuity of less than 6/60 was seen in 26% of cases. Visual acuity of 6/12 or better was achieved in 72% (p < 0.01) of cases with symptoms less than 2 weeks and in 59.10% of cases with IOP of less than 35 mm Hg at presentation. The mean IOP in cases with duration of symptoms of 2 to 4 weeks was 40.33 ± 9.36 mm Hg. Optic disk of the affected eye suffered damage in 42% of cases and in 80% of cases with symptoms for more than 2 weeks. Conclusion: Early diagnosis and treatment is beneficial in LIG cases. How to cite this article: Sharanabasamma M, Vaibhav K. Management and Visual Outcome in Patients of Lens-induced Glaucomas at a Tertiary Eye Care Hospital in South India. J Curr Glaucoma Pract 2016;10(2):68-75. PMID:27536050

  6. Therapeutic Effects of Sodium Hyaluronate on Ocular Surface Damage Induced by Benzalkonium Chloride Preserved Anti-glaucoma Medications

    PubMed Central

    Liu, Xing; Yu, Fen-Fen; Zhong, Yi-Min; Guo, Xin-Xing; Mao, Zhen

    2015-01-01

    Background: Long-term use of benzalkonium chloride (BAC)-preserved drugs is often associated with ocular surface toxicity. Ocular surface symptoms had a substantial impact on the glaucoma patients’ quality of life and compliance. This study aimed to investigate the effects of sodium hyaluronate (SH) on ocular surface toxicity induced by BAC-preserved anti-glaucoma medications treatment. Methods: Fifty-eight patients (101 eyes), who received topical BAC-preserved anti-glaucoma medications treatment and met the severe dry eye criteria, were included in the analysis. All patients were maintained the original topical anti-glaucoma treatment. In the SH-treated group (56 eyes), unpreserved 0.3% SH eye drops were administered with 3 times daily for 90 days. In the control group (55 eyes), phosphate-buffered saline were administered with 3 times daily for 90 days. Ocular Surface Disease Index (OSDI) questionnaire, break-up time (BUT) test, corneal fluorescein staining, corneal and conjunctival rose Bengal staining, Schirmer test, and conjunctiva impression cytology were performed sequentially on days 0 and 91. Results: Compared with the control group, SH-treated group showed decrease in OSDI scores (Kruskal-Wallis test: H = 38.668, P < 0.001), fluorescein and rose Bengal scores (Wilcoxon signed-ranks test: z = −3.843, P < 0.001, and z = −3.508, P < 0.001, respectively), increase in tear film BUT (t-test: t = −10.994, P < 0.001) and aqueous tear production (t-test: t = −10.328, P < 0.001) on day 91. The goblet cell density was increased (t-test: t = −9.981, P < 0.001), and the morphology of the conjunctival epithelium were also improved after SH treatment. Conclusions: SH significantly improved both symptoms and signs of ocular surface damage in patients with BAC-preserved anti-glaucoma medications treatment. SH could be proposed as a new attempt to reduce ocular surface toxicity, and alleviate symptoms of ocular surface damage in BAC-preserved anti-glaucoma

  7. Magnetically induced pulser laser excitation

    SciTech Connect

    Taylor, R.S.; Leopold, K.E.

    1985-02-15

    A novel excitation scheme has been developed for excimer discharge lasers. The technique uses pulse transformer technology to induce a fast, high voltage pulse directly onto a ground potential laser electrode resulting in the breakdown of the laser gas mix. Saturation of the pulse transformer core inductance then permits efficient energy transfer from the main energy storage circuit into the discharge. When this excitation technique was used in a XeCl laser an output energy density of 2.5 J/l and an overall electrical to optical efficiency of 2% were obtained. The technique appears promising for the development of high energy, high average power excimer lasers.

  8. [The refractory glaucomas].

    PubMed

    Valtot, F

    2003-10-01

    Refractory types of glaucoma continue to present a therapeutic challenge to ophthalmologists. Approaches toward the management of these difficult glaucomas are addressed in this paper. The first part devotes special attention to understand the cause(s) of the failure of previous filtering surgery(ies). The next part emphasizes filtration surgery with intraoperative application of antimetabolites: 5-fluorouracil or mitomycin C and the surgical and pharmacological management of failing filtration. In case of failure of multiple filtering surgery with application of antimetabolites, surgeons have to consider cyclodestructive procedures (transscleral diode laser or endoscopic cyclophotocoagulation) to reduce aqueous production, or fistulizing procedures with tube implants or other drainage devices (valves). PMID:14646834

  9. Long-term Follow-up of a Case of Gold Shunt Surgery for Refractory Silicone Oil–induced Glaucoma

    PubMed Central

    Le, Ryan; Berger, Alan R.

    2016-01-01

    Purpose: To report the first case of gold shunt surgery for treatment of silicone oil–induced refractory glaucoma in a tertiary care academic center, with 5-year follow-up. Design: The study design is a case report. Participants: The participant was a patient who underwent gold shunt surgery. Methods: Institutional Research Ethics Board approval for the study was obtained. A diabetic patient was referred for refractory glaucoma with a history of proliferative diabetic retinal detachment, and surgery with silicone oil. She was uncontrolled on maximal medical therapy and following informed consent, gold shunt surgery was performed. Ocular outcomes and number of medications were reviewed over a 5-year period. Results: Following uncomplicated surgery, intraocular pressure was reduced from 41 to 14 mm Hg, and the number of medications was reduced from 4 to 1. Glaucomatous optic neuropathy remained stable. Conclusions: Gold shunt surgery in this challenging case of silicone oil refractory glaucoma provided long-term intraocular pressure control and reduced need for medication over a 5-year period. PMID:27253968

  10. Intraocular Pressure-Lowering Potential of Subthreshold Selective Laser Trabeculoplasty in Patients with Primary Open-Angle Glaucoma

    PubMed Central

    Yang, Yang Fan; Xu, Jian Gang

    2016-01-01

    Purpose. To compare the efficacy of subthreshold and conventional selective laser trabeculoplasty (SLT) in lowering intraocular pressure (IOP) in the patients with primary open-angle glaucoma (POAG). Methods. Fifty-two eyes from fifty-two POAG patients were randomized into two groups, one group treated with subthreshold SLT using two-thirds of the conventional energy and the other one treated with the conventional energy. IOP was measured with the Goldmann tonometer and the anterior chamber inflammation was determined using laser flare meter. Results. The initial energy dosage used in subthreshold SLT group was significantly lower than the amount of the energy used in conventional SLT group (0.4 ± 0.1 mJ versus 0.6 ± 0.1 mJ, P = 0.030). The total energy dosage was also significantly lower in subthreshold SLT group compared to the other group (37.6 ± 3.3 mJ versus 51.8 ± 5.7 mJ, P = 0.036). However, the level of inflammation in aqueous humor, amount of reduction in IOP, and the success rate in controlling IOP was the same in both groups. Conclusion. The efficacy of subthreshold SLT group in reducing IOP in POAG patients is comparable to the efficacy of conventional SLT group. PMID:27529032

  11. Intraocular Pressure-Lowering Potential of Subthreshold Selective Laser Trabeculoplasty in Patients with Primary Open-Angle Glaucoma.

    PubMed

    Zhang, Hong Yang; Qin, Yong Jie; Yang, Yang Fan; Xu, Jian Gang; Yu, Min Bin

    2016-01-01

    Purpose. To compare the efficacy of subthreshold and conventional selective laser trabeculoplasty (SLT) in lowering intraocular pressure (IOP) in the patients with primary open-angle glaucoma (POAG). Methods. Fifty-two eyes from fifty-two POAG patients were randomized into two groups, one group treated with subthreshold SLT using two-thirds of the conventional energy and the other one treated with the conventional energy. IOP was measured with the Goldmann tonometer and the anterior chamber inflammation was determined using laser flare meter. Results. The initial energy dosage used in subthreshold SLT group was significantly lower than the amount of the energy used in conventional SLT group (0.4 ± 0.1 mJ versus 0.6 ± 0.1 mJ, P = 0.030). The total energy dosage was also significantly lower in subthreshold SLT group compared to the other group (37.6 ± 3.3 mJ versus 51.8 ± 5.7 mJ, P = 0.036). However, the level of inflammation in aqueous humor, amount of reduction in IOP, and the success rate in controlling IOP was the same in both groups. Conclusion. The efficacy of subthreshold SLT group in reducing IOP in POAG patients is comparable to the efficacy of conventional SLT group. PMID:27529032

  12. Managing advanced unilateral pseudoexfoliative glaucoma.

    PubMed

    Marques, André

    2014-01-01

    The only proven therapy for glaucoma is intraocular pressure (IOP) reduction, which can be accomplished by different means. Each should be properly discussed with patients in order to best preserve visual function and quality of life. We report a case of unilateral pseudoexfoliative glaucoma, treated for years with triple topical IOP-lowering drugs. The patient presented with advanced optic neuropathy and important ocular side effects secondary to the treatment. Having discussed his options and prognosis, laser trabeculoplasty was performed while maintaining the remaining therapy considering the advanced stage of glaucoma. His IOP was effectively reduced and no progression was noted after 1-year follow-up. Although medical therapy is the mainstream in glaucoma management, its side effects should not be ignored, especially in unilateral cases. Surgery might have been a better solution, but we chose to perform laser trabeculoplasty, an effective and safer alternative, considering the unlikely but serious risk of the "wipe-out phenomenon" in this case. PMID:24850557

  13. Managing advanced unilateral pseudoexfoliative glaucoma.

    PubMed

    Marques, André

    2014-01-01

    The only proven therapy for glaucoma is intraocular pressure (IOP) reduction, which can be accomplished by different means. Each should be properly discussed with patients in order to best preserve visual function and quality of life. We report a case of unilateral pseudoexfoliative glaucoma, treated for years with triple topical IOP-lowering drugs. The patient presented with advanced optic neuropathy and important ocular side effects secondary to the treatment. Having discussed his options and prognosis, laser trabeculoplasty was performed while maintaining the remaining therapy considering the advanced stage of glaucoma. His IOP was effectively reduced and no progression was noted after 1-year follow-up. Although medical therapy is the mainstream in glaucoma management, its side effects should not be ignored, especially in unilateral cases. Surgery might have been a better solution, but we chose to perform laser trabeculoplasty, an effective and safer alternative, considering the unlikely but serious risk of the "wipe-out phenomenon" in this case.

  14. Glaucoma Research Foundation

    MedlinePlus

    ... born with glaucoma. Read her story » Learn About Glaucoma Glaucoma is a complicated disease in which damage ... Booklet Vision Loss Progression healthy advanced Tips for Glaucoma Care We've worked with patients, researchers, and ...

  15. Feline Glaucoma.

    PubMed

    McLellan, Gillian J; Teixeira, Leandro B C

    2015-11-01

    Feline glaucoma is often insidious in onset and slowly progressive with very subtle clinical signs. As a consequence, it is likely that the disease in cats is underdiagnosed. As cats typically present late in the course of disease, prognosis for long-term maintenance of vision is poor. Patient and owner compliance with frequent application of topical medications can be a limiting factor, and represents a serious clinical challenge. This review outlines the clinical features, classification, and pathophysiology of the feline glaucomas and provides current evidence on which to base the selection of appropriate treatment strategies for cats with glaucoma.

  16. Laser Induced Blue Luminescence Phenomenon

    NASA Astrophysics Data System (ADS)

    Zhu, Haiyong; Duan, Yanmin; Zhang, Ge; Zhang, Yaoju; Yang, Fugui

    2011-09-01

    Laser induced strange blue luminescence in several Raman crystals has been investigated. The blue luminescence at about 473 nm has the characteristic of no orientation and only produced in the crystal where the fundament laser oscillated. The experimental results show that the blue luminescence must result from the fundamental laser around 1.0 µm rather than Stokes-shifting. The spectrum detected is similar for different crystals. This blue luminescence is obviously strange and inconsistent with traditional luminescence theories, which maybe a brand-new luminescence theory.

  17. Induced pluripotent stem cells restore function in a human cell loss model of open-angle glaucoma.

    PubMed

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-03-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option.

  18. Induced pluripotent stem cells restore function in a human cell loss model of open-angle glaucoma.

    PubMed

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-03-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option. PMID:25377070

  19. Acute glaucoma following vitrectomy and silicone oil injection.

    PubMed Central

    Zborowski-Gutman, L; Treister, G; Naveh, N; Chen, V; Blumenthal, M

    1987-01-01

    Three cases are described of acute glaucoma following vitrectomy and silicone oil injection in proliferative vitreous retinopathy. The first case developed silicone-induced pupillary block in a phakic eye. Cases 2 and 3 developed elevated pressure in aphakic eyes with deep anterior chambers. Cases 1 and 3 were treated by laser iridectomy. Case 2 was treated by removal of silicone. The pathogenesis and treatment of these problems are discussed. PMID:3426996

  20. Inducible scAAV2.GRE.MMP1 lowers IOP long-term in a large animal model for steroid-induced glaucoma gene therapy

    PubMed Central

    Borrás, Teresa; Buie, LaKisha K.; Spiga, Maria Grazia

    2016-01-01

    Current treatment of glaucoma relies on administration of daily drops or eye surgery. A gene therapy approach to treat steroid-induced glaucoma would bring a resolution to millions of people worldwide that depend on glucocorticoid therapy for a myriad of inflammatory disorders. Previously, we had characterized a short-term Adh.GRE.MMP1 gene vector for the production of steroid-induced MMP1 in the trabecular meshwork and tested reduction of elevated intraocular pressure (IOP) in a sheep model. Here we conducted a trial transferring the same transgene cassette to a clinically safe vector (scAAV2), and extended the therapeutic outcome to longer periods of times. No evidence of ocular and/or systemic toxicity was observed. Viral genome distributions showed potential re-inducible vector DNAs in the trabecular meshwork (0.4 vg/cell) and negligible copies in six major internal organs (0.00002-0.005 vg/cell). Histological sections confirmed successful transduction of scAAV2.GFP to the trabecular meshwork. Optimization of the sheep steroid–induced hypertensive model revealed that topical ophthalmic drug difluprednate 0.05% (durezol) induced the highest IOP elevation in the shortest time. This is the first efficacy/toxicity study of a feasible gene therapy treatment of steroid-induced hypertension using clinically accepted scAAV vectors in a large animal model. PMID:26855269

  1. Can Visual Field Progression be Predicted by Confocal Scanning Laser Ophthalmoscopic Imaging of the Optic Nerve Head in Glaucoma? (An American Ophthalmological Society Thesis)

    PubMed Central

    Danias, John; Serle, Janet

    2015-01-01

    Purpose: To determine whether confocal scanning laser ophthalmoscopic imaging (Heidelberg retinal tomography [HRT]) can predict visual field change in glaucoma. Methods: The study included 561 patients with glaucoma or ocular hypertension whose clinical course was followed at the Mount Sinai Faculty practice. Humphrey visual fields (HVFs) and HRT images were collected on one randomly selected eye per patient. Glaucoma progression was determined by the presence of two sequential statistically significant negative slopes in mean deviation (MD) or visual field index (VFI) at any point during the study period. Trend-based analysis on HRT parameters was used to determine progressive changes and whether these occurred before or after HVF change. Sensitivity and specificity of HRT to predict HVF change were calculated. HVF rate of change was correlated to the rate of change detected by HRT imaging. Results: Approximately 17% of patients progressed by either MD or VFI criteria. MD and VFI correlated highly and identified overlapping sets of patients as progressing. HRT global parameters had poor sensitivity (∼42%) and moderate specificity (∼67%) to predict HVF progression. Regional stereometric parameters were more sensitive (69%–78%) but significantly less specific (24%–27%). Sensitivity of global stereometric parameters in detecting HVF change was not significantly affected by the level of visual field damage (P=.3, Fisher exact test). HVF rate of change did not correlate with rate of change of HRT parameters. Conclusions: Trend-based analysis of HRT parameters has poor sensitivity and specificity in predicting HVF change. This may be related specifically to HRT imaging or may reflect the fact that in some patients with glaucoma, functional changes precede structural alterations. PMID:26549913

  2. Transpupillary Argon Laser Cyclophotocoagulation in a Refractory Traumatic Glaucoma Patient with Aphakia and Aniridia

    PubMed Central

    Uzunel, Umut Duygu; Yüce, Berna; Küsbeci, Tuncay; Ateş, Halil

    2016-01-01

    We present a case of transpupillary argon laser cyclophotocoagulation (TALC) in a patient with traumatic aniridia and aphakia secondary to blunt trauma who had previous bilateral trabeculectomy. Four months after the trauma the patient’s intraocular pressure (IOP) rose to 35 mmHg despite topical antiglaucomatous medication. Inferior 180 degrees cyclophotocoagulation was performed with transpupillary argon laser in the first session and his IOP fell to values of 12-17 mmHg. Twelve weeks after TALC, his IOP rose to 22 mmHg and we had to apply TALC to the residual ciliary processes. Seven months later his IOP was 13 mmHg with topical dorzolamide/timolol and latanoprost administration. TALC may be an effective treatment alternative for lowering IOP in patients with visible ciliary processes who do not respond to conventional medical or laser treatment. PMID:27800256

  3. Nonpenetrating glaucoma surgery using the CO2 laser: experimental studies in human cadaver eyes

    NASA Astrophysics Data System (ADS)

    Assia, Ehud I.; Barequet, Irina S.; Rosner, Mordechai; Belkin, Michael

    2001-06-01

    Non-penetrating trabeculectomy (NPT) is a potential replacement to conventional trabeculectomy, as it eliminates the necessity of penetrating the eye which is the cause of most of the complications entailed by the latter operation. NPT however, requires considerable surgical skill, is time consuming and entails complications of its own. We have shown that it can be easily performed by using the CO2 laser to ablate the sclera and corneoscleral tissues to the required depth. The use of the CO2 laser eliminates the danger of inadvertent perforation, a common complication of NPT as the tissue ablation ceases when the end-point of the operation, the aqueous humor percolation, is reached. Our experiments, performed on animal and human cadaver eyes showed that CO2 laser NPT rapid is easily mastered and performed rapid and eliminates almost completely the risk of complications.

  4. Glaucoma risk index: automated glaucoma detection from color fundus images.

    PubMed

    Bock, Rüdiger; Meier, Jörg; Nyúl, László G; Hornegger, Joachim; Michelson, Georg

    2010-06-01

    Glaucoma as a neurodegeneration of the optic nerve is one of the most common causes of blindness. Because revitalization of the degenerated nerve fibers of the optic nerve is impossible early detection of the disease is essential. This can be supported by a robust and automated mass-screening. We propose a novel automated glaucoma detection system that operates on inexpensive to acquire and widely used digital color fundus images. After a glaucoma specific preprocessing, different generic feature types are compressed by an appearance-based dimension reduction technique. Subsequently, a probabilistic two-stage classification scheme combines these features types to extract the novel Glaucoma Risk Index (GRI) that shows a reasonable glaucoma detection performance. On a sample set of 575 fundus images a classification accuracy of 80% has been achieved in a 5-fold cross-validation setup. The GRI gains a competitive area under ROC (AUC) of 88% compared to the established topography-based glaucoma probability score of scanning laser tomography with AUC of 87%. The proposed color fundus image-based GRI achieves a competitive and reliable detection performance on a low-priced modality by the statistical analysis of entire images of the optic nerve head.

  5. Get Tested for Glaucoma!

    MedlinePlus

    ... of this page please turn Javascript on. Feature: Glaucoma Get Tested for Glaucoma! Past Issues / Fall 2009 Table of Contents Taylor ... aoa.org/ When were you finally diagnosed with glaucoma? Not until 1969, after a game of basketball. ...

  6. [Glaucoma medications, preservatives and the ocular surface.

    PubMed

    Aptel, F; Labbé, A; Baudouin, C; Bron, A; Lachkar, Y; Sellem, E; Renard, J-P; Nordmann, J-P; Rouland, J-F; Denis, P

    2014-10-14

    Several clinical and experimental studies have demonstrated that ocular surface disease is common in glaucoma patients receiving chronic glaucoma drops, and that the preservatives in these drops play a major role in the occurrence of ocular surface disease. These ocular surface changes may induce both symptoms reported by the patients and anterior segment clinical signs, and should be systematically assessed by history and exam in all glaucoma patients. In these patients with ocular surface disease, reducing the amount of preservatives administered to the eye should be strived for, rather than adding additional eye drops to alleviate or mask the side effects of the glaucoma drops. PMID:25440185

  7. Modeling of scanning laser polarimetry images of the human retina for progression detection of glaucoma.

    PubMed

    Vermeer, Koen A; Vos, Frans M; Lo, Barrick; Zhou, Qienyuan; Lemij, Hans G; Vossepoel, Albert M; van Vliet, Lucas J

    2006-05-01

    The development of methods to detect slowly progressing diseases is often hampered by the time-consuming acquisition of a sufficiently large data set. In this paper, a method is presented to model the change in images acquired by scanning laser polarimetry, for the detection of glaucomatous progression. The model is based on image series of 23 healthy eyes and incorporates colored noise, incomplete cornea compensation and masking by the retinal blood vessels. Additionally, two methods for detecting progression, taking either one or two follow-up visits into account, are discussed and tested on these simulated images. Both methods are based on Student's t-tests, morphological operations and anisotropic filtering. The images simulated by the model are visually pleasing, show corresponding statistical properties to the real images and are used to optimize the detection methods. The results show that detecting progression based on two follow-up visits greatly improves the sensitivity without adversely affecting the specificity.

  8. Pressure-Induced Alterations in PEDF and PEDF-R Expression: Implications for Neuroprotective Signaling in Glaucoma

    PubMed Central

    Lee, Sean J; Duncan, D’Anne S; Echevarria, Franklin D; McLaughlin, William M; Hatcher, Jeremy B; Sappington, Rebecca M

    2015-01-01

    Introduction Alterations in neuron-glia signaling are implicated in glaucoma, a neurodegenerative disease characterized by retinal ganglion cell (RGC) death. Pigment epithelium derived factor (PEDF) is a secreted protein with potential neuroprotective qualities in retinal disease, including chronic ocular hypertension. Here we sought to determine whether moderate, short-term elevations in IOP alter PEDF signaling and whether pressure-induced PEDF signaling directly impacts RGC apoptosis. Methods In retina from naïve mice and mice with unilateral, microbead-induced glaucoma, we examined expression and cell type-specific localization of PEDF and its receptor (PEDF-R), using quantitative PCR and immunohistochemistry. Using primary cultures of purified RGCs and Müller cells, we examined cell type-specific expression of PEDF in response to 48 hours of elevated hydrostatic pressure, using multiplex ELISA and immunocytochemistry. We also measured pressure-induced apoptosis of RGCs in the presence or absence of atglistatin, a potent and selective inhibitor of PEDF-R, and recombinant PEDF, using TUNEL assays. Results PEDF and PEDF-R are constitutively expressed in naïve retina, primarily in the ganglion cell and nerve fiber layers. Elevated IOP increases PEDF and PEDF-R expression, particularly associated with RGCs and Müller cells. Elevated pressure in vitro increased PEDF secretion by 6-fold in RGCs and trended towards an increase in expression by Müller cells, as compared to ambient pressure. This was accompanied by changes in the subcellular localization of PEDF-R in both cell types. Inhibition of PEDF signaling with atglistatin increased pressure-induced apoptosis in RGCs and treatment with recombinant PEDF inhibited pressure-induced apoptosis, both in a dose-dependent manner. Conclusion Our findings suggest that moderate, short-term elevations in IOP promote PEDF signaling via up-regulation of both PEDF and PEDF-R. Based on in vivo and in vitro studies, this PEDF

  9. Acquired color vision loss and a possible mechanism of ganglion cell death in glaucoma.

    PubMed Central

    Nork, T M

    2000-01-01

    PURPOSE: First, to study the cellular mechanisms of acquired color vision loss in retinal detachment and diabetic retinopathy. Second, to learn why, in glaucoma, the type of color vision deficit that is observed is more characteristic of a retinal injury than it is of an optic neuropathy. Third, to test a hypothesis of photoreceptor-induced, ganglion cell death in glaucoma. METHODS: Various histologic techniques were employed to distinguish the L/M-cones (long/medium wavelength-sensitive cones, or red/green sensitive cones) from the S-cones (short wavelength-sensitive cones, or blue sensitive cones) in humans and monkeys with retinal detachment, humans with diabetic retinopathy, and both humans and monkeys with glaucoma. To test if the photoreceptors were contributing to ganglion cell death, laser photocoagulation was used in a experimental model of glaucoma to focally eliminate the photoreceptors. As a control, optic nerve transection was done following retinal laser photocoagulation in one animal. RESULTS: Selective and widespread loss of the S-cones was found in retinal detachment as well as diabetic retinopathy. By contrast, in human as well as experimental glaucoma, marked swelling of the L/M-cones was the predominant histopathologic feature. Retinal laser photocoagulation followed by experimental glaucoma resulted in selective protection of ganglion cells overlying the laser spots. This was not seen with retinal laser photocoagulation by optic nerve transection. CONCLUSIONS: In retinal detachment and diabetic retinopathy, acquired tritan-like color vision loss could be caused, or contributed to, by selective loss of the S-cones. Both L- and M-cones are affected in glaucoma, which is also consistent with a tritan-like deficit. Although not a therapeutic option, protection of ganglion cells by retinal laser in experimental glaucoma is consistent with an hypothesis of anterograde, photoreceptor-induced, ganglion cell death. Images FIGURE 1 FIGURE 2 FIGURE 3

  10. Laser-induced chromatic adaptation

    SciTech Connect

    Schmeisser, E.T.

    1988-08-01

    Detecting a target in a visually noisy back-ground depends on the ability of the observer to discriminate the target from the surrounding terrain. Visible laser irradiation at less than damage levels may act as a masking source by reducing the observer's ability to resolve differences in the visual scene. The experiment reported here specifically investigates the comparability of shuttered CW and Q-switched visible lasers to alter/degrade color discrimination. Visual evoked potentials (VEP's) were used to examine the short time course effects in monkeys of luminance-matched flashes from a 694 nm ruby Q-switched laser and 100 ms shuttered krypton CW laser (676, 568, and 531 nm lines). The test stimulus was a shifting pattern of alternating luminance-matched 510 and 550 nm green bars. With flashes equated to 4.8 log T-s, similar flash effect curves were seen, demonstrating 1.5-s changes in response magnitude. This level of flash did not extinguish the response to the stimulus. The flash effects curve was ''W''-shaped, with an intermediate signal peak occurring at approximately 500 ms after the flash and whose level exceeded the baseline magnitude. The hypothesized mechanism for this result is an induced luminance imbalance caused by a transient shift in the peak color responsiveness of the visual system, which recovers with two different time constants. It is concluded that red and green colored laser flashes shift the color balance transiently in the visual system (yellow flashes to a lesser extent); thus, targets may change both hue and brightness after an observer receives colored flashes.

  11. Glaucoma risks in advanced corneal surgery.

    PubMed

    Maurino, Vincenzo; Aiello, Francesco

    2015-01-01

    Penetrating corneal transplant (PKP) surgery has been performed for centuries as the procedure of choice to restore vision in cases of advanced corneal disease. However, the last two decades have seen the introduction of lamellar corneal surgery (deep anterior lamellar keratoplasty, DALK; Descemet stripping-automated endothelial keratoplasty, DSAEK; and Descemet membrane endothelial keratoplasty, DMEK) which has shown several advantages over PKP and has rapidly gained popularity, given its benefits. Glaucoma after corneal graft surgery is an important cause of visual loss and graft failure. The main risk factors for developing glaucoma after any type of corneal graft are steroid-related intraocular hypertension and pre-existing glaucoma. The incidence of glaucoma after corneal graft surgery varies according to the specific risk factors and the type of corneal graft performed. One major advantage of modern layer selective lamellar keratoplasty is the reduced risk of glaucoma compared with PKP. This reduced glaucoma risk after corneal lamellar graft surgery is mainly due to the less destructive surgical nature of the lamellar procedures and also the reduced use of postoperative steroid treatment. Glaucoma can complicate not only corneal transplantation but has also been observed following other anterior segment procedures from laser refractive surgery to keratoprosthesis. The aim of this chapter is to describe the incidence, etiology, and management of glaucoma after corneal transplant and some common corneal surgical procedures.

  12. Resveratrol prevents the expression of glaucoma markers induced by chronic oxidative stress in trabecular meshwork cells

    PubMed Central

    Luna, Coralia; Li, Guorong; Liton, Paloma B; Qiu, Jianming; Epstein, David L.; Challa, Pratap; Gonzalez, Pedro

    2009-01-01

    Elevated intraocular pressure (IOP) constitutes the best characterized risk for primary open-angle glaucoma (POAG). Elevated IOP is believed to result from an increase in aqueous humor outflow resistance at the level of the trabecular meshwork (TM)/ Schlemm's canal (SC). Malfunction of the TM in POAG is associated with the expression of markers for inflammation, cellular senescence, oxidative damage, and decreased cellularity. Current POAG treatments rely on lowering IOP, but there is no therapeutic approach available to delay the loss of function of the TM in POAG patients. We evaluated the effects of chronic administration of the dietary supplement resveratrol on the expression of markers for inflammation, oxidative damage, and cellular senescence in primary TM cells subjected to chronic oxidative stress (40% O2). Resveratrol treatment effectively prevented increased production of intracellular reactive oxygen species (iROS) and inflammatory markers (IL1α, IL6, IL8, and ELAM-1), and reduced expression of the senescence markers sa-β-gal, lipofuscin, and accumulation of carbonylated proteins. Furthermore, resveratrol exerted antiapoptotic effects that were not associated with a decrease in cell proliferation. These results suggest that resveratrol could potentially have a role in preventing the TM tissue abnormalities observed in POAG. PMID:19027816

  13. Uveitis and glaucoma: new insights in the pathogenesis and treatment.

    PubMed

    Sng, Chelvin C A; Ang, Marcus; Barton, Keith

    2015-01-01

    Glaucoma is a potentially blinding complication of uveitis, where intraocular inflammation, secondary corticosteroid response, and varying types and degrees of angle abnormalities contribute to its pathogenesis. Management of uveitic glaucoma remains challenging. Treatment is targeted at reducing the inflammation and lowering the intraocular pressure. Recent studies have highlighted the role of viruses, such as cytomegalovirus, herpes simplex virus, and more recently Ebola virus, in the pathogenesis of uveitic glaucoma. Antiviral therapy may be beneficial in eyes with detectable viral DNA. The success of glaucoma surgery is decreased in eyes with uveitic glaucoma, and surgical interventions are associated with a higher incidence of postoperative complications. Novel glaucoma surgical and laser treatments may improve the predictability of surgery for uveitic glaucoma, but these require further evaluation.

  14. Laser induced biological heating analyzed

    NASA Astrophysics Data System (ADS)

    Liu, Phue

    1985-08-01

    A quantitative analysis of the vaporization of tumors by pulsed CO2 lasers, incision by CW CO2 lasers, tissue coagulation by argon lasers, thermal killing of cancerous cells by He-Ne lasers, and the application of heat by CO2 lasers is presented. Although the calculations are based on a simplified skin model, it may prove useful in clinical treatments.

  15. Management of exfoliative glaucoma: challenges and solutions

    PubMed Central

    Holló, Gábor; Katsanos, Andreas; Konstas, Anastasios GP

    2015-01-01

    Exfoliative glaucoma is the most common type of secondary open-angle glaucoma worldwide. It is characterized by high intraocular pressure (IOP) and worse 24-hour IOP characteristics. In order to minimize progression, treatment of exfoliative glaucoma has to provide a low long-term mean IOP and good 24-hour IOP control. To achieve these goals, fixed-dose combination eye drops, argon and selective laser trabeculoplasty, and various forms of surgery (trabeculectomy, deep sclerectomy, viscocanalostomy, ab interno trabeculotomy, trabecular aspiration, and cataract surgery) all need to be considered during the long-term management of the disease. Since exfoliative glaucoma is a disease of the elderly, and is frequently associated with systemic vascular disease, interdisciplinary consultations are of great clinical importance. These management aspects and the current medical, laser, and surgical results are covered in this review, with a special focus on the needs of the general ophthalmologist. PMID:26045655

  16. Management of exfoliative glaucoma: challenges and solutions.

    PubMed

    Holló, Gábor; Katsanos, Andreas; Konstas, Anastasios Gp

    2015-01-01

    Exfoliative glaucoma is the most common type of secondary open-angle glaucoma worldwide. It is characterized by high intraocular pressure (IOP) and worse 24-hour IOP characteristics. In order to minimize progression, treatment of exfoliative glaucoma has to provide a low long-term mean IOP and good 24-hour IOP control. To achieve these goals, fixed-dose combination eye drops, argon and selective laser trabeculoplasty, and various forms of surgery (trabeculectomy, deep sclerectomy, viscocanalostomy, ab interno trabeculotomy, trabecular aspiration, and cataract surgery) all need to be considered during the long-term management of the disease. Since exfoliative glaucoma is a disease of the elderly, and is frequently associated with systemic vascular disease, interdisciplinary consultations are of great clinical importance. These management aspects and the current medical, laser, and surgical results are covered in this review, with a special focus on the needs of the general ophthalmologist.

  17. Secondary glaucoma in CAPN5-associated neovascular inflammatory vitreoretinopathy

    PubMed Central

    Cham, Abdourahman; Bansal, Mayank; Banda, Himanshu K; Kwon, Young; Tlucek, Paul S; Bassuk, Alexander G; Tsang, Stephen H; Sobol, Warren M; Folk, James C; Yeh, Steven; Mahajan, Vinit B

    2016-01-01

    Objective The objective of this study was to review the treatment outcomes of patients with secondary glaucoma in cases of autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV), a hereditary autoimmune uveitis due to mutations in CAPN5. Patients and methods A retrospective, observational case series was assembled from ADNIV patients with secondary glaucoma. The main outcome measures were intraocular pressure (IOP), visual acuity, use of antiglaucoma medications, ocular surgeries, and adverse outcomes. Perimetry and optic disk optical coherence tomography (OCT) were also analyzed. Results Nine eyes of five ADNIV patients with secondary glaucoma were reviewed. Each received a fluocinolone acetonide (FA) implant for the management of posterior uveitis. Following implantation, no eyes developed neovascular glaucoma. Five eyes (in patients 1, 2, and 5) required Ahmed glaucoma valve surgery for the management of steroid-responsive glaucoma. Patient 2 also developed angle closure with iris bombe and underwent laser peripheral iridotomy. Patient 4 had both hypotony and elevated IOP that required periodic antiglaucoma medication in the FA-implanted eye. Patient 3 did not develop steroid-response glaucoma in either eye. Optic disk examinations were obscured by fibrosis and better assessed with OCT. Conclusion ADNIV patients show combined mechanism secondary glaucoma best assessed by OCT of the optic disk. The FA implants have reduced uveitic and neovascular glaucoma. Nevertheless, IOP management remains complex due to steroid-response glaucoma, angle closure glaucoma, and hypotony. PMID:27390515

  18. Ultrasound for noninvasive control of laser-induced tissue heating and coagulation

    NASA Astrophysics Data System (ADS)

    Kleffner, Bernhard; Kriegerowski, Martin; Oltrup, Theo; Bende, Thomas; Jean, Benedikt J.

    1996-05-01

    The application of lasers to achieve localized thermal tissue damage is a common technique in minimally invasive surgery. Currently, there is no control during these treatments. In glaucoma therapy the laser energy applied and the beam direction are estimated prior to treatment, according to clinical experience and anatomic norm values. This lack of on-line control may limit success and lead to side effects. Precision and efficiency of treatment could be improved markedly by analysis of spatially resolved, temperature-dependent data obtained by Ultrasound Reflectometry. Thermally induced changes, as well as their localization were detected qualitatively in B-scan. Quantification was achieved by integration of high frequency RF-signals with the following resolution: spatial 50 micrometers , temporal 200 microsecond(s) , temperature 0.5 degree(s). The presented method is suitable for a non-invasive on-line therapy control.

  19. [The place of SLT in managing glaucoma].

    PubMed

    Nordmann, J-P

    2008-07-01

    Selective laser trabeculoplasty (SLT) is effective in reducing intraocular pressure (IOP) in glaucomatous patients and patients with ocular hypertension. Equivalent to argon laser trabeculoplasty in terms of IOP reduction, SLT has the advantage of preserving surrounding structures. Easy and rapid to perform, SLT may be an interesting therapeutic approach in the management of glaucoma. PMID:18957918

  20. Screening for Glaucoma

    MedlinePlus

    ... enough evidence to determine the potential benefits and harms of glaucoma screening for adults who do not ... Glaucoma is a group of diseases that can harm the eye’s optic nerve. The optic nerve carries ...

  1. Glaucoma in Asian Populations

    MedlinePlus

    ... Us Donate In This Section Glaucoma In Asian Populations email Send this article to a friend by ... an even more serious problem as the world population and longevity increases. The other major glaucoma type ...

  2. Interaction of Laser Induced Micro-shockwaves

    NASA Astrophysics Data System (ADS)

    Leela, Ch.; Bagchi, Suman; Tewari, Surya P.; Kiran, P. Prem

    Laser induced Shock Waves (LISWs) characterized by several optical methods provide Equation of State (EOS) for a variety of materials used in high-energy density physics experiments at Mbar pressures [1, 2]. Other applications include laser spark ignition for fuel-air mixtures, internal combustion engines, pulse detonation engines, laser shock peening [3], surface cleaning [4] and biological applications (SW lithotripsy) [5] to name a few.

  3. Glaucoma eye drops adverse skin reactions.

    PubMed

    Cantisani, Carmen; Ambrifi, Marina; Frascani, Federica; Fazia, Gilda; Paolino, Giovanni; Lisi, Roberto; Calvieri, Stefano

    2014-01-01

    The term "Glaucoma" is used to describe a number of diseases of the eye characterized by a particular form of optic nerve damage that is often associated with high intraocular pressure (IOP). The open-angle glaucoma is the most common form that is also referred to as chronic glaucoma. This is described as an optic neuropathy with multifactorial nature in which there is a loss of characteristics of the optic nerve fibers. Therapeutic options for the treatment of this disease are different, you can take advantage of eye drops, laser therapy and conventional surgery or more combined treatments. Medicated eye drops are the most common way to treat glaucoma. Although eye drops are widely used, adverse reactions are not frequently observed and described. In particular, the adverse skin reactions are not frequently described in the literature, but often seen in dermatologic clinic, we reported their skin reactions and possible alternative treatments described in literature and their patent applications. PMID:25487259

  4. Laser-induced shockwave lithotripsy of gallstones.

    PubMed

    Ell, C; Wondrazek, F; Frank, F; Hochberger, J; Lux, G; Demling, L

    1986-05-01

    With the aid of a Q-switched Nd:YAG laser with energy transmission via a flexible glass fiber, it proves possible under laboratory conditions, to destroy gallstones reliably and reproducibly. Lithotripsy is effected mechanically via a laser-induced local shockwave.

  5. Laser Induced Chemical Liquid Phase Deposition (LCLD)

    SciTech Connect

    Nanai, Laszlo; Balint, Agneta M.

    2012-08-17

    Laser induced chemical deposition (LCLD) of metals onto different substrates attracts growing attention during the last decade. Deposition of metals onto the surface of dielectrics and semiconductors with help of laser beam allows the creation of conducting metal of very complex architecture even in 3D. In the processes examined the deposition occurs from solutions containing metal ions and reducing agents. The deposition happens in the region of surface irradiated by laser beam (micro reactors). Physics -chemical reactions driven by laser beam will be discussed for different metal-substrate systems. The electrical, optical, mechanical properties of created interfaces will be demonstrated also including some practical-industrial applications.

  6. Laser-induced caesium-137 decay

    NASA Astrophysics Data System (ADS)

    Barmina, E. V.; Simakin, A. V.; Shafeev, G. A.

    2014-08-01

    Experimental data are presented on the laser-induced beta decay of caesium-137. We demonstrate that the exposure of a gold target to a copper vapour laser beam (wavelengths of 510.6 and 578.2 nm, pulse duration of 15 ns) for 2 h in an aqueous solution of a caesium-137 salt reduces the caesium-137 activity by 70%, as assessed from the gamma activity of the daughter nucleus 137mBa, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal.

  7. Laser-induced caesium-137 decay

    SciTech Connect

    Barmina, E V; Simakin, A V; Shafeev, G A

    2014-08-31

    Experimental data are presented on the laser-induced beta decay of caesium-137. We demonstrate that the exposure of a gold target to a copper vapour laser beam (wavelengths of 510.6 and 578.2 nm, pulse duration of 15 ns) for 2 h in an aqueous solution of a caesium-137 salt reduces the caesium-137 activity by 70%, as assessed from the gamma activity of the daughter nucleus {sup 137m}Ba, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal. (letters)

  8. Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma.

    PubMed

    Song, Wei-tao; Zhang, Xue-yong; Xia, Xiao-bo

    2015-05-01

    Glaucoma is one of the leading eye diseases resulting in blindness due to the death of retinal ganglion cells. This study aimed to develop novel protocol to promote the differentiation of retinal Müller cells into ganglion cells in vivo in a rat model of glaucoma. The stem cells dedifferentiated from rat retinal Müller cells were randomized to receive transfection with empty lentivirus PGC-FU-GFP or lentivirus PGC-FU-Atoh7-GFP, or no transfection. The stem cells were induced further to differentiate. Ocular hypertension was induced using laser photocoagulation. The eyes were injected with Atoh7 expression vector lentivirus PGC-FU-Atoh7-GFP. Eyeball frozen sections, immunohistochemistry, RT-PCR, Western bolt, and apoptosis assay were performed. We found that the proportion of ganglion cells differentiated from Atoh7-tranfected stem cells was significantly higher than that of the other two groups. The mean intraocular pressure of glaucomatous eyes was elevated significantly compared with those of contralateral eyes. Some retinal Müller cells in the inner nuclear layer entered the mitotic cell cycle in rat chronic ocular hypertension glaucoma model. Atoh7 contributes to the differentiation of retinal Müller cells into retinal ganglion cells in rat model of glaucoma. In conclusion, Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma, thus opening up a new avenue for gene therapy and optic nerve regeneration in glaucoma.

  9. Genetic bases for glaucoma.

    PubMed

    Fuse, Nobuo

    2010-05-01

    Glaucoma is the leading cause of visual impairment and blindness throughout the world. Primary open angle glaucoma (POAG; MIM 137760) is the main type of glaucoma in most populations, and more than 20 genetic loci for POAG have been reported. Only three causative genes have been identified in these loci, viz. myocilin (MYOC), optineurin (OPTN), and WD repeat domain 36 (WDR36). However, mutations in these genes account for only a small percentage of the patients with POAG. Some of these glaucoma cases have a Mendelian inheritance pattern, and a considerable fraction of the cases result from a large number of variants in several genes each contributing small effects. Glaucoma is considered to be a common disease such as diabetes mellitus, coronary disease, Crohn disease, and several( )common cancers. The main technological approaches used to identify the genes associated with glaucoma are the candidate gene approach, linkage analysis, case-control association study, and genome-wide association study. Association studies have found about 27 genes related to POAG, but the glaucoma-causing effects of these genes need to be investigated in more detail. The current trend is to use case-control association studies or genome-wide association studies to map the genes associated with glaucoma. Such studies are expected to greatly advance our understanding of the genetic basis of glaucoma, and to provide information on the effectiveness of glaucoma therapy. This review gives an overview on the genetic aspects of glaucoma.

  10. Glaucoma Surgery in Pregnancy: A Case Series and Literature Review

    PubMed Central

    Razeghinejad, Mohammad Reza; Masoumpour, Masoumeh; Eghbal, Mohammad Hossein; Myers, Jonathan S.; Moster, Marlene R.

    2016-01-01

    Glaucoma management in pregnant patients is a real challenge, especially when the glaucoma is not controlled with medications. We report the results of 6 incisional glaucoma surgeries for the management of medically uncontrolled glaucoma patients during pregnancy. This retrospective, case series was conducted on the 6 eyes of 3pregnant patients with uncontrolled glaucoma using maximum tolerable medications. Details of the glaucoma surgical management of these patients as well as their postoperative care and pregnancy and clinical outcomes on longitudinal follow-up are discussed. All 3 patients had juvenile open-angle glaucoma and were on various anti-glaucoma medications, including oral acetazolamide. The first case described underwent trabeculectomy without antimetabolites in both eyes because of uncontrolled intraocular pressure with topical medications. The surgery was done with topical lidocaine jelly and subconjunctival lidocaine during the second and third trimesters. The second patient had an Ahmed valve implantation in both eyes during the second and third trimesters because of uncontrolled IOP with topical medications and no response to selective laser trabeculoplasty. Surgery was done with topical tetracaine and subconjunctival and sub-Tenon’s lidocaine. The third case had a Baerveldt valve implantation under general anesthesia in the second trimester. In selected pregnant glaucoma patients with medically uncontrolled intraocular pressure threatening vision, incisional surgery may lead to good outcomes for the patient with no risk for the fetus. PMID:27582594

  11. Glaucoma Surgery in Pregnancy: A Case Series and Literature Review.

    PubMed

    Razeghinejad, Mohammad Reza; Masoumpour, Masoumeh; Eghbal, Mohammad Hossein; Myers, Jonathan S; Moster, Marlene R

    2016-09-01

    Glaucoma management in pregnant patients is a real challenge, especially when the glaucoma is not controlled with medications. We report the results of 6 incisional glaucoma surgeries for the management of medically uncontrolled glaucoma patients during pregnancy. This retrospective, case series was conducted on the 6 eyes of 3pregnant patients with uncontrolled glaucoma using maximum tolerable medications. Details of the glaucoma surgical management of these patients as well as their postoperative care and pregnancy and clinical outcomes on longitudinal follow-up are discussed. All 3 patients had juvenile open-angle glaucoma and were on various anti-glaucoma medications, including oral acetazolamide. The first case described underwent trabeculectomy without antimetabolites in both eyes because of uncontrolled intraocular pressure with topical medications. The surgery was done with topical lidocaine jelly and subconjunctival lidocaine during the second and third trimesters. The second patient had an Ahmed valve implantation in both eyes during the second and third trimesters because of uncontrolled IOP with topical medications and no response to selective laser trabeculoplasty. Surgery was done with topical tetracaine and subconjunctival and sub-Tenon's lidocaine. The third case had a Baerveldt valve implantation under general anesthesia in the second trimester. In selected pregnant glaucoma patients with medically uncontrolled intraocular pressure threatening vision, incisional surgery may lead to good outcomes for the patient with no risk for the fetus. PMID:27582594

  12. Does Marijuana Help Treat Glaucoma?

    MedlinePlus

    ... Ophthalmologist Patient Stories Español Eye Health / Tips & Prevention Marijuana Sections Does Marijuana Help Treat Glaucoma? Why Eye ... Don't Recommend Marijuana for Glaucoma Infographic Does Marijuana Help Treat Glaucoma? Written by: David Turbert , contributing ...

  13. Zeeman effect induced by intense laser light.

    PubMed

    Stambulchik, E; Maron, Y

    2014-08-22

    We analyze spectral line shapes of hydrogenlike species subjected to fields of electromagnetic waves. It is shown that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman effect induced by a visible or infrared light can be experimentally observed using present-day powerful lasers. In addition, the effect may be used for diagnostics of focused beam intensities achieved at existing and newly built laser facilities. PMID:25192094

  14. Heat pump processes induced by laser radiation

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.

    1980-01-01

    A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

  15. Zeeman effect induced by intense laser light.

    PubMed

    Stambulchik, E; Maron, Y

    2014-08-22

    We analyze spectral line shapes of hydrogenlike species subjected to fields of electromagnetic waves. It is shown that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman effect induced by a visible or infrared light can be experimentally observed using present-day powerful lasers. In addition, the effect may be used for diagnostics of focused beam intensities achieved at existing and newly built laser facilities.

  16. Induced Current Characteristics Due to Laser Induced Plasma and Its Application to Laser Processing Monitoring

    SciTech Connect

    Madjid, Syahrun Nur; Idris, Nasrullah; Kurniawan, Koo Hendrik

    2011-03-30

    In laser processing, suitable conditions for laser and gas play important role in ensuring a high quality of processing. To determine suitable conditions, we employed the electromagnetic phenomena associated with laser plasma generation. An electrode circuit was utilised to detect induced current due to the fast electrons propelled from the material during laser material processing. The characteristics of induced current were examined by changing parameters such as supplied voltage, laser pulse energy, number of laser shots, and type of ambient gas. These characteristics were compared with the optical emission characteristics. It was shown that the induced current technique proposed in this study is much more sensitive than the optical method in monitoring laser processing, that is to determine the precise focusing condition, and to accurately determine the moment of completion of laser beam penetration. In this study it was also shown that the induced current technique induced by CW CO{sub 2} laser can be applied in industrial material processing for monitoring the penetration completion in a stainless steel plate drilling process.

  17. Electromagnetically induced transparency with noisy lasers

    SciTech Connect

    Xiao Yanhong; Wang Tun; Baryakhtar, Maria; Jiang Liang; Lukin, Mikhail D.; Van Camp, Mackenzie; Crescimanno, Michael; Hohensee, Michael; Walsworth, Ronald L.; Phillips, David F.; Yelin, Susanne F.

    2009-10-15

    We demonstrate and characterize two coherent phenomena that can mitigate the effects of laser phase noise for electromagnetically induced transparency (EIT): a laser-power-broadening-resistant resonance in the transmitted intensity cross correlation between EIT optical fields, and a resonant suppression of the conversion of laser phase noise to intensity noise when one-photon noise dominates over two-photon-detuning noise. Our experimental observations are in good agreement with both an intuitive physical picture and numerical calculations. The results have wide-ranging applications to spectroscopy, atomic clocks, and magnetometers.

  18. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-01

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized.

  19. Ultraviolet radiation induced discharge laser

    DOEpatents

    Gilson, Verle A.; Schriever, Richard L.; Shearer, James W.

    1978-01-01

    An ultraviolet radiation source associated with a suitable cathode-anode electrode structure, disposed in a gas-filled cavity of a high pressure pulsed laser, such as a transverse electric atmosphere (TEA) laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and the cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby providing volume ionization of the gas. The ultraviolet radiation is produced by a light source or by a spark discharge.

  20. Laser Induced Breakdown Spectroscopy of Metals

    NASA Astrophysics Data System (ADS)

    Palmer, Andria; Lawhead, Carlos; Ujj, Laszlo

    2015-03-01

    Laser Induced Breakdown Spectroscopy (LIBS) is a very practical spectroscopy to determine the chemical composition of materials. Recent technical developments resulted in equipment used on the MARS Rover by NASA. It is capable of measuring the emission spectra of laser induced plasma created by energetic laser pulses focused on the sample (rocks, metals, etc.). We have develop a Laser Induced Breakdown Spectroscopy setup and investigated the necessary experimental and methodological challenges needed to make such material identification measurements. 355 and 532 nm laser pulses with 5 ns temporal duration was used to generate micro-plasma from which compositions can be determined based on known elemental and molecular emission intensities and wavelengths. The performance of LIBS depends on several parameters including laser wavelength, pulse energy, pulse duration, time interval of observation, geometrical configuration of collecting optics, and the properties of ambient medium. Spectra recorded from alloys (e.g. US penny coin) and pure metals will be presented. Special thanks for the financial support of the Office of Undergraduate Research of UWF.

  1. 24-h Efficacy of Glaucoma Treatment Options.

    PubMed

    Konstas, Anastasios G P; Quaranta, Luciano; Bozkurt, Banu; Katsanos, Andreas; Garcia-Feijoo, Julian; Rossetti, Luca; Shaarawy, Tarek; Pfeiffer, Norbert; Miglior, Stefano

    2016-04-01

    Current management of glaucoma entails the medical, laser, or surgical reduction of intraocular pressure (IOP) to a predetermined level of target IOP, which is commensurate with either stability or delayed progression of visual loss. In the published literature, the hypothesis is often made that IOP control implies a single IOP measurement over time. Although the follow-up of glaucoma patients with single IOP measurements is quick and convenient, such measurements often do not adequately reflect the untreated IOP characteristics, or indeed the quality of treated IOP control during the 24-h cycle. Since glaucoma is a 24-h disease and the damaging effect of elevated IOP is continuous, it is logical that we should aim to understand the efficacy of all treatment options throughout the 24-h period. This article first reviews the concept and value of diurnal and 24-h IOP monitoring. It then critically evaluates selected available evidence on the 24-h efficacy of medical, laser and surgical therapy options. During the past decade several controlled trials have significantly enhanced our understanding on the 24-h efficacy of all glaucoma therapy options. Nevertheless, more long-term evidence is needed to better evaluate the 24-h efficacy of glaucoma therapy and the precise impact of IOP characteristics on glaucomatous progression and visual prognosis.

  2. Benzalkonium Chloride and Glaucoma

    PubMed Central

    Kaufman, Paul L.; Kiland, Julie A.

    2014-01-01

    Abstract Glaucoma patients routinely take multiple medications, with multiple daily doses, for years or even decades. Benzalkonium chloride (BAK) is the most common preservative in glaucoma medications. BAK has been detected in the trabecular meshwork (TM), corneal endothelium, lens, and retina after topical drop installation and may accumulate in those tissues. There is evidence that BAK causes corneal and conjunctival toxicity, including cell loss, disruption of tight junctions, apoptosis and preapoptosis, cytoskeleton changes, and immunoinflammatory reactions. These same effects have been reported in cultured human TM cells exposed to concentrations of BAK found in common glaucoma drugs and in the TM of primary open-angle glaucoma donor eyes. It is possible that a relationship exists between chronic exposure to BAK and glaucoma. The hypothesis that BAK causes/worsens glaucoma is being tested experimentally in an animal model that closely reflects human physiology. PMID:24205938

  3. Mestastable State Population in Laser Induced Plasmas

    NASA Technical Reports Server (NTRS)

    Kwong, V. H. S.; Kyriakides, C.; Ward, W. K.

    2006-01-01

    Laser induced plasma has been used as a source of neutrals and ions in the study of astrophysical plasmas. The purity of state of this source is essential in the determination of collision parameters such as the charge transfer rate coefficients between ions and neutrals. We will show that the temperature of the laser induced plasma is a rapidly decreasing function of time. The temperature is initially high but cools off rapidly through collisions with the expanding plasma electrons as the plasma recombines and streams into the vacuum. This rapid expansion of the plasma, similar to a supersonic jet, drastically lowers the internal energy of the neutrals and ions.

  4. Laser-induced desorption from sapphire surfaces

    SciTech Connect

    Hamza, A.V.; Schildbach, M.A.

    1992-03-01

    Laser-induced desorption of energetic ({approximately}7eV) aluminum ions was observed from clean and water-covered sapphire (1102) surfaces using time-of-flight mass spectrometry with laser wavelengths of 1064, 355, and 266 nm. In sharp contrast, O{sup +} (H{sup +} and OH{sup +}) ions were observed in electron-induced desorption measurements with 300 eV electrons from the bare (water- covered) (1102) surface. Sapphire surfaces were characterized with low energy electron diffraction, reflection electron energy loss spectroscopy, and Auger electron spectroscopy. 8 refs.

  5. Psychological Aspects of Glaucoma.

    PubMed

    Jeong, Ah Reum; Kim, Chan Yun; Kang, Min Hee; Kim, Na Rae

    2016-03-01

    Glaucoma is a group of optic neuropathies that is more prevalent among the elderly population and commonly associates with comorbidities, including mental disorders in that population. This article reviews the relationship between glaucoma and mental disorders. In it, we discuss the coexistence of glaucoma and mental illnesses, including Alzheimer's disease, depression, and personality disorder. We also focus on the proper treatment approaches for glaucoma patients with mental comorbidity and poor treatment adherence. We summarize some cautiously recommended psychotherapeutic medications, while also discussing the psychologically adverse effects of antiglaucoma medications.

  6. Laser induced phosphorescence uranium analysis

    DOEpatents

    Bushaw, B.A.

    1983-06-10

    A method is described for measuring the uranium content of aqueous solutions wherein a uranyl phosphate complex is irradiated with a 5 nanosecond pulse of 425 nanometer laser light and resultant 520 nanometer emissions are observed for a period of 50 to 400 microseconds after the pulse. Plotting the natural logarithm of emission intensity as a function of time yields an intercept value which is proportional to uranium concentration.

  7. Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.; Jenkins, Luther N.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

  8. Application Of Laser Coagulation In Retinal Detachment And Open - Angle Glaucoma, On The Basis Of Own Experiments

    NASA Astrophysics Data System (ADS)

    Palacz, Olgierd; Karczewicz, Danuta; Owczarska, Wieslawa; Sylwestrzak, Zofia

    1987-10-01

    The first part of the paper presents the results of laser ¬Â¢hotocoaculation treatment involving: 141 patients with retinal detachment , 20 with holes in the macula, and 33 with holes at the eye fundus periphery. At estimating the results, the apposition of retina and the observation time have been taken into account. The second part contains the results of observation of 21 patients, in whom, in 26 eyes laser trabeculoplasty was performed. Normalization of intraocular pressure has been obtained in 76.9% of cases. The outflow coefficient after trabeculoplasty has increased in 57.6% of cases.

  9. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  10. Metabolomics of the aqueous humor in the rat glaucoma model induced by a series of intracamerular sodium hyaluronate injection.

    PubMed

    Mayordomo-Febrer, A; López-Murcia, M; Morales-Tatay, J M; Monleón-Salvado, D; Pinazo-Durán, M D

    2015-02-01

    Glaucoma models are helpful to study disease characteristics and to design new therapeutic options. Metabolomic profiling approach have been used to elucidating the molecular characteristics of the aqueous humor. Juvenile male Wistar rats experimental (n = 15) and controls (n = 6) were used for these studies. Experimental rats received weekly intracamerular injection of 25 µl of sodium hyaluronate in the left eye and sterile saline solution in the right eye, consecutively for ten weeks. Rats were subjected to anterior/posterior eye segment examinations, intraocular pressure (IOP), and flash electroretinograms (ERG). The aqueous humor was collected at endpoints and analyzed by Nuclear Magnetic Resonance. Elevated IOP and significant reduction of a, b waves and amplitude of oscillatory potential was observed in the left eyes compared to control eyes. The aqueous humor metabolomic profile from control and the experimental eyes were compared. Concentrations of metabolites (amino acids, lipids and carbohydrates) significantly changed after the sodium hyaluronate injections series, compared to the sham-operated eyes. Metabolic changes in the hypertensive eyes correlated with the impaired retinal function. Observed metabolomic changes in aqueous humor in hypertensive state may play a significant role in glaucoma pathogenesis.

  11. Laser-induced lipolysis on adipose cells

    NASA Astrophysics Data System (ADS)

    Solarte, Efrain; Gutierrez, O.; Neira, Rodrigo; Arroyave, J.; Isaza, Carolina; Ramirez, Hugo; Rebolledo, Aldo F.; Criollo, Willian; Ortiz, C.

    2004-10-01

    Recently, a new liposuction technique, using a low-level laser (LLL) device and Ultrawet solution prior to the procedure, demonstrated the movement of fat from the inside to the outside of the adipocyte (Neira et al., 2002). To determine the mechanisms involved, we have performed Scanning and Transmission Electron Microscopy studies; Light transmittance measurements on adipocyte dilutions; and a study of laser light propagation in adipose tissue. This studies show: 1. Cellular membrane alterations. 2. LLL is capable to reach the deep adipose tissue layer, and 3. The tumescence solution enhances the light propagation by clearing the tissue. MRI studies demonstrated the appearance of fat on laser treated abdominal tissue. Besides, adipocytes were cultivated and irradiated to observe the effects on isolated cells. These last studies show: 1. 635 nm-laser alone is capable of mobilizing cholesterol from the cell membrane; this action is enhanced by the presence of adrenaline and lidocaine. 2. Intracellular fat is released from adipocytes by co joint action of adrenaline, aminophyline and 635 nm-laser. Results are consistent with a laser induced cellular process, which causes fat release from the adipocytes into the intercellular space, besides the modification of the cellular membranes.

  12. [Vascular factors in glaucoma].

    PubMed

    Mottet, B; Aptel, F; Geiser, M; Romanet, J P; Chiquet, C

    2015-12-01

    The exact pathophysiology of glaucoma is not fully understood. Understanding of the vascular pathophysiology of glaucoma requires: knowing the techniques for measuring ocular blood flow and characterizing the topography of vascular disease and the mechanisms involved in this neuropathy. A decreased mean ocular perfusion pressure and a loss of vascular autoregulation are implicated in glaucomatous disease. Early decrease in ocular blood flow has been identified in primary open-angle glaucoma and normal pressure glaucoma, contributing to the progression of optic neuropathy. The vascular damage associated with glaucoma is present in various vascular territories within the eye (from the ophthalmic artery to the retina) and is characterized by a decrease in basal blood flow associated with a dysfunction of vasoregulation.

  13. Corneal thickness in glaucoma.

    PubMed

    De Cevallos, E; Dohlman, C H; Reinhart, W J

    1976-02-01

    The central corneal stromal thickness of patients with open angle glaucoma, secondary glaucoma (the majority aphakic), or a history of unilateral acute angle closure glaucoma were measured and compared with the stromal thickness of a group of normal patients. In open angle glaucoma, there was a small but significant increase in the average stromal thickness. This thickness increase was, in all likelihood, due to an abnormal function of the endothelium in this disease since the level of the intraocular pressure did not seem to be a factor. There was no correlation between stromal thickness and duration of the glaucoma or type of anti-glaucomatous medication. Most cases of secondary glaucome, controlled medically or not, had markedly increased corneal thickness, again, most likely, due to endothelial damage rather than to level of intraocular pressure. After an angle closure attack, permanent damage to the cornea was found to be rare. PMID:1247273

  14. [Vascular factors in glaucoma].

    PubMed

    Mottet, B; Aptel, F; Geiser, M; Romanet, J P; Chiquet, C

    2015-12-01

    The exact pathophysiology of glaucoma is not fully understood. Understanding of the vascular pathophysiology of glaucoma requires: knowing the techniques for measuring ocular blood flow and characterizing the topography of vascular disease and the mechanisms involved in this neuropathy. A decreased mean ocular perfusion pressure and a loss of vascular autoregulation are implicated in glaucomatous disease. Early decrease in ocular blood flow has been identified in primary open-angle glaucoma and normal pressure glaucoma, contributing to the progression of optic neuropathy. The vascular damage associated with glaucoma is present in various vascular territories within the eye (from the ophthalmic artery to the retina) and is characterized by a decrease in basal blood flow associated with a dysfunction of vasoregulation. PMID:26597554

  15. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  16. Laser induced fluorescence technique for environmental applications

    NASA Astrophysics Data System (ADS)

    Utkin, Andrei B.; Felizardo, Rui; Gameiro, Carla; Matos, Ana R.; Cartaxana, Paulo

    2014-08-01

    We discuss the development of laser induced fluorescence sensors and their application in the evaluation of water pollution and physiological status of higher plants and algae. The sensors were built on the basis of reliable and robust solid-state Nd:YAG lasers. They demonstrated good efficiency in: i) detecting and characterizing oil spills and dissolved organic matter; ii) evaluating the impact of stress on higher plants (cork oak, maritime pine, and genetically modified Arabidopsis); iii) tracking biomass changes in intertidal microphytobenthos; and iv) mapping macroalgal communities in the Tagus Estuary.

  17. Kinetic Approach for Laser-Induced Plasmas

    SciTech Connect

    Omar, Banaz; Rethfeld, Baerbel

    2008-10-22

    Non-equilibrium distribution functions of electron gas and phonon gas excited with ultrashort intense laser pulses are calculated for laser-induced plasmas occurring in solids. The excitation during femtosecond irradiation and the subsequent thermalization of the free electrons, as well as the dynamics of phonons are described by kinetic equations. The microscopic collision processes, such as absorption by inverse bremsstrahlung, electron-electron collisions, and electron-phonon interactions are considered by complete Boltzmann collision integrals. We apply our kinetic approach for gold by taking s-band electron into account and compare it with the case of excitation of d-band electrons.

  18. Laser-Induced Incandescence: Detection Issues

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.

    1996-01-01

    Experimental LII (laser-induced incandescence) measurements were performed in a laminar gasjet flame to test the sensitivity of different LII signal collection strategies to particle size. To prevent introducing a particle size dependent bias in the LII signal, signal integration beginning with the excitation laser pulse is necessary . Signal integration times extending to 25 or 100 nsec after the laser pulse do not produce significant differences in radial profiles of the LII signal due to particle size effects with longer signal integration times revealing a decreased sensitivity to smaller primary particles. Long wavelength detection reduces the sensitivity of the LII signal to primary particle size. Excitation of LII using 1064 nm light is recommended to avoid creating photochemical interferences thus allowing LII signal collection to occur during the excitation pulse without spectral interferences.

  19. Minimally invasive glaucoma surgery: current status and future prospects

    PubMed Central

    Richter, Grace M; Coleman, Anne L

    2016-01-01

    Minimally invasive glaucoma surgery aims to provide a medication-sparing, conjunctival-sparing, ab interno approach to intraocular pressure reduction for patients with mild-to-moderate glaucoma that is safer than traditional incisional glaucoma surgery. The current approaches include: increasing trabecular outflow (Trabectome, iStent, Hydrus stent, gonioscopy-assisted transluminal trabeculotomy, excimer laser trabeculotomy); suprachoroidal shunts (Cypass micro-stent); reducing aqueous production (endocyclophotocoagulation); and subconjunctival filtration (XEN gel stent). The data on each surgical procedure for each of these approaches are reviewed in this article, patient selection pearls learned to date are discussed, and expectations for the future are examined. PMID:26869753

  20. Minimally invasive glaucoma surgery: current status and future prospects.

    PubMed

    Richter, Grace M; Coleman, Anne L

    2016-01-01

    Minimally invasive glaucoma surgery aims to provide a medication-sparing, conjunctival-sparing, ab interno approach to intraocular pressure reduction for patients with mild-to-moderate glaucoma that is safer than traditional incisional glaucoma surgery. The current approaches include: increasing trabecular outflow (Trabectome, iStent, Hydrus stent, gonioscopy-assisted transluminal trabeculotomy, excimer laser trabeculotomy); suprachoroidal shunts (Cypass micro-stent); reducing aqueous production (endocyclophotocoagulation); and subconjunctival filtration (XEN gel stent). The data on each surgical procedure for each of these approaches are reviewed in this article, patient selection pearls learned to date are discussed, and expectations for the future are examined.

  1. Minimally invasive glaucoma surgery: current implants and future innovations.

    PubMed

    SooHoo, Jeffrey R; Seibold, Leonard K; Radcliffe, Nathan M; Kahook, Malik Y

    2014-12-01

    Traditionally, invasive surgical management of glaucoma is recommended when medication and/or laser trabeculoplasty fail to control intraocular pressure (IOP). Filtering procedures, such as trabeculectomy and glaucoma drainage devices, are effective in lowering IOP, but they have significant associated adverse events and rates of failure. For these reasons, a new group of surgical procedures has emerged that seeks to decrease IOP with lower associated rates of complications. The acronym MIGS, usually described as minimally invasive glaucoma surgery, has been coined to describe this group of procedures. As new devices become available, MIGS procedures will help to fill the gap between conservative medical and laser therapy and invasive surgical treatment of glaucoma to offer patients an earlier and safer transition to surgical management of their disease. In this review, we define the characteristics of an ideal MIGS procedure and discuss implants currently in use or under investigation.

  2. Management of Primary Angle-Closure Glaucoma.

    PubMed

    Lai, Jimmy; Choy, Bonnie N K; Shum, Jennifer W H

    2016-01-01

    Primary angle-closure glaucoma (PACG) is a progressive optic nerve degeneration and is defined as a glaucomatous optic neuropathy with associated characteristic enlargement of optic disc cupping and visual field loss that is secondary to ocular hypertension caused by closure of the drainage angle. Angle closure is caused by appositional approximation or adhesion between the iris and the trabecular meshwork. The main treatment strategy for PACG lies in the reduction of intraocular pressure, reopening of the closed angle, and possible prevention of further angle closure. There is no universally agreed best surgical treatment for PACG. Trabeculectomy, goniosynechialysis (GSL), glaucoma implant, and cyclodestructive procedures are effective surgical options. Each of them plays an important role in the management of PACG with its own pros and cons. Accumulating evidence is available to show the effectiveness of visually significant and visually nonsignificant cataract extraction in the treatment of PACG. Trabeculectomy and GSL are often combined with cataract extraction, which may offer additional pressure control benefits to patients with PACG. This review article will discuss laser peripheral iridotomy, argon laser peripheral iridoplasty, and surgeries such as GSL, phacoemulsification, and phaco plus glaucoma surgeries that lower intraocular pressure and also alter the anterior segment and/or drainage angle anatomy. Currently, glaucoma implants and cyclodestruction are mainly reserved for PACG patients who have failed previous filtering operations. Their role as initial surgical treatment for PACG will not be discussed. PMID:26886121

  3. What Is Glaucoma?

    MedlinePlus

    ... Glaucoma is a disease that damages your eye's optic nerve. It usually happens when fluid builds up ... increases the pressure in your eye, damaging the optic nerve. It is estimated that three million Americans ...

  4. Coping with Glaucoma

    MedlinePlus Videos and Cool Tools

    ... comprehensive eye examination performed by a qualified eye care professional such as an opthalmologistor optometrist. The exam ... at-risk individuals -- that's the recommendation of eye care professionals, and that's the way to stop glaucoma ...

  5. Daily Life with Glaucoma

    MedlinePlus

    ... Close Send Thanks for emailing that article! Tweet Free Booklet You can also find the information in ... are not reflected on our website. Get Our Free Newsletter Subscribe Doctors Order booklets about glaucoma for ...

  6. African Americans and Glaucoma

    MedlinePlus

    ... Close Send Thanks for emailing that article! Tweet Free Booklet You can also find the information in ... are not reflected on our website. Get Our Free Newsletter Subscribe Doctors Order booklets about glaucoma for ...

  7. Five Common Glaucoma Tests

    MedlinePlus

    ... Close Send Thanks for emailing that article! Tweet Free Booklet You can also find the information in ... are not reflected on our website. Get Our Free Newsletter Subscribe Doctors Order booklets about glaucoma for ...

  8. [The history of glaucoma].

    PubMed

    Grewe, R

    1986-02-01

    Glaucoma has been known in medicine since Antiquity. Hippokrates described "glaykoseis" as blindness which occurs in the elderly. The English ophthalmologist Banister was the first to establish the connection between increased tension of the eyeball and glaucoma. The important invention of the ophthalmoscope by von Helmholtz (1850) made it possible to diagnose glaucomatous changes in the fundus. In 1862, Donders discovered that high intraocular pressure caused blindness and called the disease "Glaukoma simplex." Further progress in the diagnosis of glaucoma was made by the invention of the tonometer and the perimeter, and the use of cocain. The first effective surgical treatment of glaucoma, an iridectomy, was carried out by von Graefe in 1856. Drug treatment started in 1875 with the discovery of pilocarpine.

  9. Premium IOLs in Glaucoma.

    PubMed

    Ichhpujani, Parul; Bhartiya, Shibal; Sharma, Anuj

    2013-01-01

    Advanced technology or premium intraocular lenses have been developed to meet the patient expectations of perfect distance and near vision without the need for spectacles. Careful patient selection is critical when implanting these implants. This brief review focusses mainly on multifocal and toric IOLs and their application and limitations in patients with glaucoma. How to cite this article: Ichhpujani P, Bhartiya S, Sharma A. Premium IOLs in Glaucoma. J Current Glau Prac 2013;7(2): 54-57. PMID:26997783

  10. Neuroprotection in Glaucoma.

    PubMed

    Doozandeh, Azadeh; Yazdani, Shahin

    2016-01-01

    Glaucoma is a degenerative optic neuropathy characterized by retinal ganglion cell (RGC) loss and visual field defects. It is known that in some glaucoma patients, death of RGCs continues despite intraocular pressure (IOP) reduction. Neuroprotection in the field of glaucoma is defined as any treatment, independent of IOP reduction, which prevents RGC death. Glutamate antagonists, ginkgo biloba extract, neurotrophic factors, antioxidants, calcium channel blockers, brimonidine, glaucoma medications with blood regulatory effect and nitric oxide synthase inhibitors are among compounds with possible neuroprotective activity in preclinical studies. A few agents (such as brimonidine or memantine) with neuroprotective effects in experimental studies have advanced to clinical trials; however the results of clinical trials for these agents have not been conclusive. Nevertheless, lack of compelling clinical evidence has not prevented the off-label use of some of these compounds in glaucoma practice. Stem cell transplantation has been reported to halt experimental neurodegenerative disease processes in the absence of cell replacement. It has been hypothesized that transplantation of some types of stem cells activates multiple neuroprotective pathways via secretion of various factors. The advantage of this approach is a prolonged and targeted effect. Important concerns in this field include the secretion of unwanted harmful mediators, graft survival issues and tumorigenesis. Neuroprotection in glaucoma, pharmacologically or by stem cell transplantation, is an interesting subject waiting for broad and multidisciplinary collaborative studies to better clarify its role in clinical practice. PMID:27413504

  11. Neuroprotection in Glaucoma

    PubMed Central

    Doozandeh, Azadeh; Yazdani, Shahin

    2016-01-01

    Glaucoma is a degenerative optic neuropathy characterized by retinal ganglion cell (RGC) loss and visual field defects. It is known that in some glaucoma patients, death of RGCs continues despite intraocular pressure (IOP) reduction. Neuroprotection in the field of glaucoma is defined as any treatment, independent of IOP reduction, which prevents RGC death. Glutamate antagonists, ginkgo biloba extract, neurotrophic factors, antioxidants, calcium channel blockers, brimonidine, glaucoma medications with blood regulatory effect and nitric oxide synthase inhibitors are among compounds with possible neuroprotective activity in preclinical studies. A few agents (such as brimonidine or memantine) with neuroprotective effects in experimental studies have advanced to clinical trials; however the results of clinical trials for these agents have not been conclusive. Nevertheless, lack of compelling clinical evidence has not prevented the off-label use of some of these compounds in glaucoma practice. Stem cell transplantation has been reported to halt experimental neurodegenerative disease processes in the absence of cell replacement. It has been hypothesized that transplantation of some types of stem cells activates multiple neuroprotective pathways via secretion of various factors. The advantage of this approach is a prolonged and targeted effect. Important concerns in this field include the secretion of unwanted harmful mediators, graft survival issues and tumorigenesis. Neuroprotection in glaucoma, pharmacologically or by stem cell transplantation, is an interesting subject waiting for broad and multidisciplinary collaborative studies to better clarify its role in clinical practice. PMID:27413504

  12. HRT for the Diagnosis and Detection of Glaucoma Progression

    PubMed Central

    Maslin, Jessica S; Mansouri, Kaweh; Dorairaj, Syril K

    2015-01-01

    Confocal scanning laser ophthalmoscopy through the Heidelberg Retina Tomograph (HRT) provides a rapid, safe, noncontact, and noninvasive imaging of the optic disc in three-dimensions, and provides precise detailed information about the optic disc beyond that which the clinical exam can measure. The HRT I was developed for research purposes only and was not used clinically. The HRT II was developed to be user-friendly, more rapid, and was used as an adjunct to clinical examination in the detection and progression of glaucoma. One of the main pitfalls of the HRT II was that it was operator-dependent. The HRT III was developed to be operator-independent. Initially the Moorsfield Regression Analysis provided the analysis of the stereometric optic disc parameters. The Glaucoma Probability Score, given its ease of use, operator-independence, and rapidity of use, soon gained popularity. Numerous studies have compared these two methods of analysis, with the conclusion that the Glaucoma Probability Score provides a higher sensitivity and a lower specificity than the Moorsfield Regression Analysis, which may indicate that it has potential as a screening test for glaucoma. However, there is no consensus on the use of the Glaucoma Probability Score as a screening test for glaucoma. While HRT data may be useful as a clinical adjunct in the screening and diagnosis of glaucoma, it should ultimately only be used to support clinical examination. PMID:26069518

  13. Glaucoma related Proteomic Alterations in Human Retina Samples

    PubMed Central

    Funke, Sebastian; Perumal, Natarajan; Beck, Sabine; Gabel-Scheurich, Silke; Schmelter, Carsten; Teister, Julia; Gerbig, Claudia; Gramlich, Oliver W.; Pfeiffer, Norbert; Grus, Franz H.

    2016-01-01

    Glaucoma related proteomic changes have been documented in cell and animal models. However, proteomic studies investigating on human retina samples are still rare. In the present work, retina samples of glaucoma and non-glaucoma control donors have been examined by a state-of-the-art mass spectrometry (MS) workflow to uncover glaucoma related proteomic changes. More than 600 proteins could be identified with high confidence (FDR < 1%) in human retina samples. Distinct proteomic changes have been observed in 10% of proteins encircling mitochondrial and nucleus species. Numerous proteins showed a significant glaucoma related level change (p < 0.05) or distinct tendency of alteration (p < 0.1). Candidates were documented to be involved in cellular development, stress and cell death. Increase of stress related proteins and decrease of new glaucoma related candidates, ADP/ATP translocase 3 (ANT3), PC4 and SRFS1-interacting protein 1 (DFS70) and methyl-CpG-binding protein 2 (MeCp2) could be documented by MS. Moreover, candidates could be validated by Accurate Inclusion Mass Screening (AIMS) and immunostaining and supported for the retinal ganglion cell layer (GCL) by laser capture microdissection (LCM) in porcine and human eye cryosections. The workflow allowed a detailed view into the human retina proteome highlighting new molecular players ANT3, DFS70 and MeCp2 associated to glaucoma. PMID:27425789

  14. Laser induced fluorescence of dental caries

    NASA Technical Reports Server (NTRS)

    Albin, S.; Byvik, C. E.; Buoncristiani, A. M.

    1988-01-01

    Significant differences between the optical spectra taken from sound regions of teeth and carious regions have been observed. These differences appear both in absorption and in laser induced fluorescence spectra. Excitation by the 488 nm line of an argon ion laser beam showed a peak in the emission intensity around 553 nm for the sound dental material while the emission peak from the carious region was red-shifted by approximately 40 nm. The relative absorption of carious region was significantly higher at 488 nm; however its fluorescence intensity peak was lower by an order of magnitude compared to the sound tooth. Implications of these results for a safe, reliable and early detection of dental caries are discussed.

  15. Nanodot formation induced by femtosecond laser irradiation

    SciTech Connect

    Abere, M. J.; Kang, M.; Goldman, R. S.; Yalisove, S. M.; Chen, C.; Rittman, D. R.; Phillips, J. D.; Torralva, B.

    2014-10-20

    The femtosecond laser generation of ZnSe nanoscale features on ZnSe surfaces was studied. Irradiation with multiple exposures produces 10–100 nm agglomerations of nanocrystalline ZnSe while retaining the original single crystal structure of the underlying material. The structure of these nanodots was verified using a combination of scanning transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The nanodots continue to grow hours after irradiation through a combination of bulk and surface diffusion. We suggest that in nanodot formation the result of ultrafast laser induced point defect formation is more than an order of magnitude below the ZnSe ultrafast melt threshold fluence. This unique mechanism of point defect injection will be discussed.

  16. Laser-induced autofluorescence of caries

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Hibst, Raimund; Flemming, Gabriela; Schneckenburger, Herbert

    1993-07-01

    The laser induced autofluorescence from carious regions of human teeth was studied using a krypton ion laser at 407 nm as an excitation source, a fiberoptical detection system combined with a polychromator and an optical multichannel analyzer. In addition, time-resolved and time-gated fluorescence measurements in the nanosecond range were carried out. It was found that carious regions contain different fluorophores which emit in the red spectral range. The emission spectra with maxima around 590 nm, 625 nm and 635 nm are typical for metalloporphyrins, copro- and protoporphyrin. During excitation the fluorescence was bleached. Non-carious regions showed a broad fluorescence band with a maximum in the short-wavelength spectral region with shorter fluorescence decay times than the carious regions. Therefore, caries can be detected by spectral analysis of the autofluorescence as well as by determination of the fluorescence decay times or by time-gated imaging.

  17. Laser-induced fluorescence imaging of bacteria

    NASA Astrophysics Data System (ADS)

    Hilton, Peter J.

    1998-12-01

    This paper outlines a method for optically detecting bacteria on various backgrounds, such as meat, by imaging their laser induced auto-fluorescence response. This method can potentially operate in real-time, which is many times faster than current bacterial detection methods, which require culturing of bacterial samples. This paper describes the imaging technique employed whereby a laser spot is scanned across an object while capturing, filtering, and digitizing the returned light. Preliminary results of the bacterial auto-fluorescence are reported and plans for future research are discussed. The results to date are encouraging with six of the eight bacterial strains investigated exhibiting auto-fluorescence when excited at 488 nm. Discrimination of these bacterial strains against red meat is shown and techniques for reducing background fluorescence discussed.

  18. Laser-induced gas-surface interactions

    NASA Astrophysics Data System (ADS)

    Chuang, T. J.

    Chemical reactions in homogeneous systems activated by laser radiation have been extensively investigated for more than a decade. The applications of lasers to promote gas-surface interactions have just been realized in recent years. The purpose of this paper is to examine the fundamental processes involved in laser-induced gas-surface chemical interactions. Specifically, the photon-enhanced adsorption, adsorbate-adsorbate and adsorbate-solid reactions, product formation and desorption processes are discussed in detail. The dynamic processes involved in photoexcitation of the electronic and vibrational states, the energy transfer and relaxation in competition with chemical interactions are considered. These include both single and multiple photon adsorption, and fundamental and overtone transitions in the excitation process, and inter- and intra-molecular energy transfer, and coupling with phonons, electron-hole pairs and surface plasmons in the energy relaxation process. Many current experimental and theoretical studies on the subject are reviewed and discussed with the goal of clarifying the relative importance of the surface interaction steps and relating the resulting concepts to the experimentally observed phenomena. Among the many gas-solid systems that have been investigated, there has been more extensive use of CO adsorbed on metals, and SF 6 and XeF 2 interactions with silicon as examples to illustrate the many facets of the electronically and vibrationally activated surface processes. Results on IR laser stimulated desorption of C 5H 5N and C 5D 5N molecules from various solid surfaces are also presented. It is clearly shown that rapid intermolecular energy exchange and molecule to surface energy transfer can have important effects on photodesorption cross sections and isotope selectivities. It is concluded that utilization of lasers in gas-surface studies not only can provide fundamental insight into the mechanism and dynamics involved in heterogeneous

  19. Improving Glaucoma Detection and Management

    ClinicalTrials.gov

    2016-11-02

    Glaucoma; Glaucoma Suspect; Diabetic Retinopathy; Ocular Hypertension; Cataract; Branch Retinal Vein Occlusion; Branch Retinal Arterial Occlusion; Central Retinal Vein Occlusion; Central Retinal Artery Occlusion; Epi-retinal Membrane; Macular Degeneration; Drusen; Loss of Vision

  20. New Tool to Predict Glaucoma

    MedlinePlus

    ... News About Us Donate In This Section A New Tool to Predict Glaucoma email Send this article ... determine if a patient has glaucoma. Recently, a new tool has become available to eye care specialists ...

  1. Diabetes and Your Eyesight (Glaucoma)

    MedlinePlus

    ... without the eye disease. Neovascular glaucoma, a rare type of glaucoma, is always associated with other abnormalities, diabetes being the most common. In some cases of diabetic retinopathy, blood vessels on the retina are damaged. ...

  2. Laser-induced breakdown spectroscopy in Asia

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Zhen; Deguchi, Yoshihiro; Zhang, Zhen-Zhen; Wang, Zhe; Zeng, Xiao-Yan; Yan, Jun-Jie

    2016-12-01

    Laser-induced breakdown spectroscopy (LIBS) is an analytical detection technique based on atomic emission spectroscopy to measure the elemental composition. LIBS has been extensively studied and developed due to the non-contact, fast response, high sensitivity, real-time and multi-elemental detection features. The development and applications of LIBS technique in Asia are summarized and discussed in this review paper. The researchers in Asia work on different aspects of the LIBS study in fundamentals, data processing and modeling, applications and instrumentations. According to the current research status, the challenges, opportunities and further development of LIBS technique in Asia are also evaluated to promote LIBS research and its applications.

  3. Caffeine administration prevents retinal neuroinflammation and loss of retinal ganglion cells in an animal model of glaucoma

    PubMed Central

    Madeira, Maria H.; Ortin-Martinez, Arturo; Nadal-Nícolas, Francisco; Ambrósio, António F.; Vidal-Sanz, Manuel; Agudo-Barriuso, Marta; Santiago, Ana Raquel

    2016-01-01

    Glaucoma is the second leading cause of blindness worldwide, being characterized by progressive optic nerve damage and loss of retinal ganglion cells (RGCs), accompanied by increased inflammatory response involving retinal microglial cells. The etiology of glaucoma is still unknown, and despite elevated intraocular pressure (IOP) being a major risk factor, the exact mechanisms responsible for RGC degeneration remain unknown. Caffeine, which is an antagonist of adenosine receptors, is the most widely consumed psychoactive drug in the world. Several evidences suggest that caffeine can attenuate the neuroinflammatory responses and afford protection upon central nervous system (CNS) injury. We took advantage of a well characterized animal model of glaucoma to investigate whether caffeine administration controls neuroinflammation and elicits neuroprotection. Caffeine or water were administered ad libitum and ocular hypertension (OHT) was induced by laser photocoagulation of the limbal veins in Sprague Dawley rats. Herein, we show that caffeine is able to partially decrease the IOP in ocular hypertensive animals. More importantly, we found that drinking caffeine prevented retinal microglia-mediated neuroinflammatory response and attenuated the loss of RGCs in animals with ocular hypertension (OHT). This study opens the possibility that caffeine or adenosine receptor antagonists might be a therapeutic option to manage RGC loss in glaucoma. PMID:27270337

  4. Laser Induced Fluorescence of the Iodine Ion

    NASA Astrophysics Data System (ADS)

    Hargus, William

    2014-10-01

    Iodine (I2) has been considered as a potential electrostatic spacecraft thruster propellant for approximately 2 decades, but has only recently been demonstrated. Energy conversion efficiency appears to be on par with xenon without thruster modification. Intriguingly, performance appears to exceed xenon at high acceleration potentials. As part of a continuing program for the development of non-intrusive plasma diagnostics for advanced plasma spacecraft propulsion, we have identified the I II 5d5D4 o state as metastable, and therefore containing a reservoir of excited state ions suitable for laser probing. The 5d5D4 o - 6p5P3 transition at 695.878 nm is convenient for diode laser excitation with the 5s5S2 o - 6p5P3 transition at 516.12 nm as an ideal candidate for non-resonant fluorescence collection. We have constructed a Penning type iodine microwave discharge lamp optimized for I II production for table-top measurements. This work demonstrates I II laser-induced fluorescence in a representative iodine discharge and will validate our previous theoretical work based on the limited available historical I II spectral data.

  5. Laser induced single spot oxidation of titanium

    NASA Astrophysics Data System (ADS)

    Jwad, Tahseen; Deng, Sunan; Butt, Haider; Dimov, S.

    2016-11-01

    Titanium oxides have a wide range of applications in industry, and they can be formed on pure titanium using different methods. Laser-induced oxidation is one of the most reliable methods due to its controllability and selectivity. Colour marking is one of the main applications of the oxidation process. However, the colourizing process based on laser scanning strategies is limited by the relative large processing area in comparison to the beam size. Single spot oxidation of titanium substrates is proposed in this research in order to increase the resolution of the processed area and also to address the requirements of potential new applications. The method is applied to produce oxide films with different thicknesses and hence colours on titanium substrates. High resolution colour image is imprinted on a sheet of pure titanium by converting its pixels' colours into laser parameter settings. Optical and morphological periodic surface structures are also produced by an array of oxide spots and then analysed. Two colours have been coded into one field and the dependencies of the reflected colours on incident and azimuthal angles of the light are discussed. The findings are of interest to a range of application areas, as they can be used to imprint optical devices such as diffusers and Fresnel lenses on metallic surfaces as well as for colour marking.

  6. [Laser-induced isotopic discrimination effect in laser resonance ionization process of lead atom].

    PubMed

    Wang, Xin-Shun; Li, Ying; Dai, Lin; Zheng, Rong-Er

    2008-07-01

    Isotope ratio measurements have been increasingly used in geochemistry, geochronology, cosmos chemistry and environmental science. Precise and accurate isotope ratio measurements are an important task in many applications such as the determination of isotope variations in geological and cosmic samples. Due to its high sensitivity, high ionization efficiency and high element selectivity, laser resonance ionization spectroscopy has nowadays become one of the key techniques, including isotope ratio measurements and trace amount analyses. Because of the isotope shifts and hyperfine structure, there is laser-induced isotopic discrimination effect in the process of laser resonance ionization. The different isotope ionization efficiency can affect precise and accurate measurement of isotope ratios. In the present paper, the dependences of the laser-induced isotopic discrimination effect on some of the laser parameters were studied by theoretical methods. Based on the numerical simulation of the population rate equations, laser-induced isotopic discrimination effect of lead isotopes was studied, by calculating laser resonance ionization transition "6s2 6p23 P0-6s2 6p7 s3 P1(0) --> ionization". The population rate equations was approximated considering some factors which affect the probability of laser resonance transition such as spectral lines width of laser and atom, isotope shifts and hyperfine structure. According to the approximated population rate equations, "1+1" laser resonant ionization process was employed to calculate the ionization probability of lead isotopes by means of computer simulation. The dependences of laser-induced isotopic discrimination effect on the laser parameters, such as laser central wavelength, bandwidth and intensity were investigated. The calculated results show that the laser-induced isotopic discrimination effect of lead isotopes could be almost eliminated by operating at optimized wavelength and could be lessened by using wide band laser

  7. Snoring and Glaucoma

    PubMed Central

    Wang, Ya Xing; Xu, Liang; Li, Jian Jun; Yang, Hua; Zhang, Ya Qin; Jonas, Jost B.

    2014-01-01

    Purpose To examine a potential association between snoring and glaucoma in a population-based setting. Methods The population-based Beijing Eye Study 2011 included 3468 subjects with an age of 50+ years. The participants underwent a detailed ophthalmic examination. Glaucoma was determined according to the ophthalmoscopic appearance of the optic nerve head. Snoring assessed in an interview was graded into “severe snoring”, “moderate snoring”, and “no snoring”. Results Data on snoring and glaucoma were available for 3146 subjects. Snoring was reported for 1787 (66.8%) subjects, with moderate snoring reported for 1384 (44.0%) subjects and severe snoring for 403 (12.8%) subjects. In multivariate analysis, prevalence of severe snoring was significantly associated with male gender (P = 0.002; regression coefficient B: 0.36; Odds ratio (OR): 1.44 (95% confidence interval (CI): 1.14, 1.81)), higher body mass index (P<0.001; B: 0.12; OR: 1.13 (95%CI: 1.09, 1.16)), higher systolic blood pressure (P<0.001; B: 0.01; OR: 1.01 (95%CI: 1.005, 1.02)), younger age (P = 0.007; B: −0.018; OR: 0.98 (95%CI: 0.97, 0.995)), and higher cognitive function (P = 0.03; B: 0.04; OR: 1.04 (95%CI: 1.004, 1.08)), however it was not significantly associated with the prevalence of open-angle glaucoma (P = 0.10; B: −0.63; OR: 0.53 (95%CI: 0.25, 1.12)). Prevalence of severe snoring was neither significantly associated with the prevalence of angle-closure glaucoma (P = 0.65), retinal vein occlusions (P = 0.24), neuroretinal rim area (P = 0.19), retinal nerve fiber layer thickness (P = 0.16) nor vertical cup/disc ratio (P = 0.64). Conclusions Severe snoring was not significantly associated with the prevalence of open-angle glaucoma, angle-closure glaucoma or retinal vein occlusions after adjustment for age, gender, body mass index, systolic blood pressure and cognitive function score. Our population-based study did not reveal that snoring was a risk

  8. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    SciTech Connect

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  9. Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma

    PubMed Central

    Song, Wei-tao; Zhang, Xue-yong

    2015-01-01

    Glaucoma is one of the leading eye diseases resulting in blindness due to the death of retinal ganglion cells. This study aimed to develop novel protocol to promote the differentiation of retinal Müller cells into ganglion cells in vivo in a rat model of glaucoma. The stem cells dedifferentiated from rat retinal Müller cells were randomized to receive transfection with empty lentivirus PGC-FU-GFP or lentivirus PGC-FU-Atoh7-GFP, or no transfection. The stem cells were induced further to differentiate. Ocular hypertension was induced using laser photocoagulation. The eyes were injected with Atoh7 expression vector lentivirus PGC-FU-Atoh7-GFP. Eyeball frozen sections, immunohistochemistry, RT-PCR, Western bolt, and apoptosis assay were performed. We found that the proportion of ganglion cells differentiated from Atoh7-tranfected stem cells was significantly higher than that of the other two groups. The mean intraocular pressure of glaucomatous eyes was elevated significantly compared with those of contralateral eyes. Some retinal Müller cells in the inner nuclear layer entered the mitotic cell cycle in rat chronic ocular hypertension glaucoma model. Atoh7 contributes to the differentiation of retinal Müller cells into retinal ganglion cells in rat model of glaucoma. In conclusion, Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma, thus opening up a new avenue for gene therapy and optic nerve regeneration in glaucoma. PMID:25710928

  10. Femtosecond laser pulse induced birefringence in optically isotropic glass.

    SciTech Connect

    Vawter, Gregory Allen; Luk, Ting Shan; Guo, Junpeng; Yang, Pin; Burns, George Robert

    2003-07-01

    We used a regeneratively amplified Ti:sapphire femtosecond laser to create optical birefringence in an isotropic glass medium. Between two crossed polarizers, regions modified by the femtosecond laser show bright transmission with respect to the dark background of the isotropic glass. This observation immediately suggests that these regions possess optical birefringence. The angular dependence of transmission through the laser-modified region is consistent with that of an optically birefringent material. Laser-induced birefringence is demonstrated in different glasses, including fused silica and borosilicate glass. Experimental results indicate that the optical axes of laser-induced birefringence can be controlled by the polarization direction of the femtosecond laser. The amount of laser-induced birefringence depends on the pulse energy level and number of accumulated pulses.

  11. Glaucoma Suspect: Diagnosis and Management.

    PubMed

    Chang, Robert T; Singh, Kuldev

    2016-01-01

    Glaucoma suspect is a diagnosis reserved for individuals who do not definitively have glaucoma at the present time but have characteristics suggesting that they are at high risk of developing the disease in the future based on a variety of factors. This review provides a practical approach to individuals classified as glaucoma suspects caused by one or more of the following risk factors or indicators of disease: ocular hypertension, optic nerve features suggestive of glaucoma, visual field abnormalities, and other characteristics placing them at greater risk than the average population. In addition to diagnostic considerations, this overview provides information on therapeutic approaches to the glaucoma suspect.

  12. [Perspectives in glaucoma surgery].

    PubMed

    Dietlein, T S

    2002-02-01

    Trabeculectomy is still considered to be the gold standard in the surgical treatment of the open-angle glaucomas. The additional application of local antimetabolites has reduced the rate of early filtering bled fibrosis, but increased the rate of essential late-postoperative complications. Growth factor inhibition and photodynamic therapy may be an alternative local treatment to enhance the results in filtering surgery. Non-penetrating glaucoma surgery and ab-interno trabecular surgery have several conceptual advantages, e.g. the lack of overfiltration or the untouched conjunctiva in the ab-interno approach. Clinical studies of these and other new procedures including antiglaucomatous retinectomy and subchoroidal shunt systems are currently performed in order to evaluate their potential and limits in the clinical management of glaucoma.

  13. Exciting directions in glaucoma.

    PubMed

    Rasmussen, Carol A; Kaufman, Paul L

    2014-12-01

    Glaucoma is a complex, life-long disease that requires an individualized, multifaceted approach to treatment. Most patients will be started on topical ocular hypotensive eyedrop therapy, and over time multiple classes of drugs will be needed to control their intraocular pressure. The search for drugs with novel mechanisms of action, to treat those who do not achieve adequate intraocular pressure control with, or become refractory to, current therapeutics, is ongoing, as is the search for more efficient, targeted drug delivery methods. Gene-transfer and stem-cell applications for glaucoma therapeutics are moving forward. Advances in imaging technologies improve our understanding of glaucoma pathophysiology and enable more refined patient evaluation and monitoring, improving patient outcomes.

  14. Update on congenital glaucoma

    PubMed Central

    Mandal, Anil K; Chakrabarti, Debasis

    2011-01-01

    Congenital glaucoma is a global problem and poses a diagnostic and therapeutic challenge to the ophthalmologist. A detailed evaluation under general anesthesia is advisable to establish the diagnosis and plan for management. Medical therapy has a limited role and surgery remains the primary therapeutic modality. While goniotomy or trabeculotomy ab externo is valuable in the management of congenital glaucoma, primary combined trabeculotomy–trabeculectomy offers the best hope of success in advanced cases. Trabeculectomy with antifibrotic agent and glaucoma drainage devices has a role in the management of refractory cases, and cyclodestructive procedures should be reserved for patients where these procedures have failed. Early diagnosis, prompt therapeutic intervention and proper refractive correction are keys to success. Management of residual vision and visual rehabilitation should be an integral part of the management of children with low vision and lifelong follow-up is a must. PMID:21150027

  15. Exciting Directions in Glaucoma

    PubMed Central

    Rasmussen, Carol A; Kaufman, Paul L

    2014-01-01

    Glaucoma is a complex, life-long disease that requires an individualized, multifaceted approach to treatment. Most patients will be started on topical ocular hypotensive eyedrop therapy and over time, multiple classes of drugs will be needed to control their intraocular pressure (IOP). The search for drugs with novel mechanisms of action, to treat those who do not achieve adequate IOP control with, or become refractory to, current therapeutics, is ongoing, as is the search for more efficient, targeted drug delivery methods. Gene transfer and stem cell applications for glaucoma therapeutics are moving forward. Advances in imaging technologies improve our understanding of glaucoma pathophysiology and enable more refined patient evaluation and monitoring, improving patient outcomes. PMID:25433744

  16. Laser-induced shockwave propagation from ablation in a cavity

    SciTech Connect

    Zeng Xianzhong; Mao Xianglei; Mao, Samuel S.; Wen, S.-B.; Greif, Ralph; Russo, Richard E.

    2006-02-06

    The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and electron number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ablation on the flat surface under the same energy and background gas condition. A theoretical model was proposed to determine the amount of energy and vaporized mass stored in the vapor plume based on these measurements.

  17. [Contrast sensitivity in glaucoma].

    PubMed

    Bartos, D

    1989-05-01

    Author reports on results of the contrast sensitivity examinations using the Cambridge low-contrast lattice test supplied by Clement Clarke International LTD, in patients with open-angle glaucoma and ocular hypertension. In glaucoma patients there was observed statistically significant decrease of the contrast sensitivity. In patients with ocular hypertension decrease of the contrast sensitivity was in patients affected by corresponding changes of the visual field and of the optical disc. The main advantages of the Cambridge low-contrast lattice test were simplicity, rapidity and precision of its performance. PMID:2743444

  18. [Consensus on neovascular glaucoma].

    PubMed

    Hamard, P; Baudouin, C

    2000-03-01

    Neovascular glaucoma is a dreadful pathology with a rapid spontaneous evolution responsible for painful and blind eye. The main cause is an anterior neovascular proliferation following a broad retinal ischemia. Early diagnosis and treatment are required in order to maintain a good visual status and a satisfactory IOP control with medical, surgical or cylodestructive procedures. In any case, the treatment of the retinal ischemia has to be performed. One must keep in mind that the most efficient way to avoid the incidence of neovascular glaucoma is a strict control of clinical situations potentially responsible for retinal ischemia, namely VRO in elderly patients and diabetic retinopathy in younger patients. PMID:10740059

  19. Laser Induced Fluorescence Spectroscopy of Cobalt Monoboride

    NASA Astrophysics Data System (ADS)

    Pang, H. F.; Ng, Y. W.; Cheung, A. S.-C.

    2011-06-01

    Laser induced fluorescence spectrum of cobalt monoboride (CoB) in the visible region between 465 and 560 nm has been observed. CoB molecule was produced by the reaction of laser ablated cobalt atom and diborane (B_2H_6) seeded in argon. Over twenty five vibronic bands have been recorded, and both Co10B and Co11B isotopic species have been observed and analyzed. Preliminary analysis of the rotational lines showed that the observed vibronic bands belong to two categories namely: the Ω' = 2 - Ω'' = 2 and the Ω' = 3 - Ω'' = 3 transitions, which indicated the ground state of CoB is consistent with an assignment of a ^3Δ_i state predicted from ab initio calculations. Unresolved hyperfine structure arising from the Co nucleus (I = 7/2) causes a broadening of spectral lines. This work represents the first experimental investigation of the spectrum of the CoB molecule. Financial support from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 701008P) is gratefully acknowledged.

  20. Volume of a laser-induced microjet

    NASA Astrophysics Data System (ADS)

    Kawamoto, Sennosuke; Hayasaka, Keisuke; Noguchi, Yuto; Tagawa, Yoshiyuki

    2015-11-01

    Needle-free injection systems are of great importance for medical treatments. In spite of their great potential, these systems are not commonly used. One of the common problems is strong pain caused by diffusion shape of the jet. To solve this problem, the usage of a high-speed highly-focused microjet as needle-free injection system is expected. It is thus crucial to control important indicators such as ejected volume of the jet for its safe application. We conduct experiments to reveal which parameter influences mostly the ejected volume. In the experiments, we use a glass tube of an inner diameter of 500 micro-meter, which is filled with the liquid. One end is connected to a syringe and the other end is opened. Radiating the pulse laser instantaneously vapors the liquid, followed by the generation of a shockwave. We find that the maximum volume of a laser-induced bubble is approximately proportional to the ejected volume. It is also found that the occurrence of cavitation does not affect the ejected volume while it changes the jet velocity.

  1. Laser-Induced Spallation of Microsphere Monolayers.

    PubMed

    Hiraiwa, Morgan; Stossel, Melicent; Khanolkar, Amey; Wang, Junlan; Boechler, Nicholas

    2016-08-01

    The detachment of a semiordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained using an adhesive contact model together with interferometric measurements of the out-of-plane microsphere contact resonance, and with estimated work of adhesion values for the polystyrene-aluminum interface. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to the fields of microsphere adhesion and contact dynamics, and demonstrates a unique monolayer delamination morphology. PMID:27409715

  2. Laser-induced breakdown spectroscopy in China

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Yuan, Ting-Bi; Hou, Zong-Yu; Zhou, Wei-Dong; Lu, Ji-Dong; Ding, Hong-Bin; Zeng, Xiao-Yan

    2014-08-01

    Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

  3. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    NASA Astrophysics Data System (ADS)

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided.

  4. Microcantilever Actuation by Laser Induced Photoacoustic Waves.

    PubMed

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  5. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    PubMed Central

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  6. Laser-induced fluorescence-cued, laser-induced breakdown spectroscopy biological-agent detection

    SciTech Connect

    Hybl, John D.; Tysk, Shane M.; Berry, Shaun R.; Jordan, Michael P

    2006-12-01

    Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS test bed has been developed and used to evaluate the utility of LIBS for biological-agent detection. Analysis of these data indicates that LIBS adds discrimination capability to fluorescence-based biological-agent detectors.However, the data also show that LIBS signatures of biological agent simulants are affected by washing. This may limit the specificity of LIBS and narrow the scope of its applicability in biological-agent detection.

  7. Laser-induced fluorescence-cued, laser-induced breakdown spectroscopy biological-agent detection.

    PubMed

    Hybl, John D; Tysk, Shane M; Berry, Shaun R; Jordan, Michael P

    2006-12-01

    Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS test bed has been developed and used to evaluate the utility of LIBS for biological-agent detection. Analysis of these data indicates that LIBS adds discrimination capability to fluorescence-based biological-agent detectors. However, the data also show that LIBS signatures of biological agent simulants are affected by washing. This may limit the specificity of LIBS and narrow the scope of its applicability in biological-agent detection.

  8. The Ahmed Glaucoma Valve in Neovascular Glaucoma (An AOS Thesis)

    PubMed Central

    Netland, Peter A.

    2009-01-01

    Purpose: To evaluate the results of Ahmed glaucoma valve surgery in neovascular glaucoma and control patients. Methods: In this retrospective comparative study, we reviewed 76 eyes of 76 patients, comparing the surgical outcomes in control patients (N=38) to matched neovascular glaucoma patients (N=38). Success was defined as intraocular pressure (IOP) ≥6 mm Hg and ≤21 mm Hg, without further glaucoma surgery, and without loss of light perception. Results: Average follow-up for control and neovascular glaucoma patients was 18.4 and 17.4 months, respectively (P = .550). At last follow-up, mean IOP was 16.2 ± 5.2 mm Hg and 15.5 ± 12.5 mm Hg (P = .115) in control and neovascular glaucoma patients, respectively. Life-table analysis showed a significantly lower success for neovascular glaucoma patients compared with controls (P = .0096), with success at 1 year of 89.2% and 73.1%, at 2 years of 81.8% and 61.9%, and at 5 years of 81.8% and 20.6% for control and neovascular glaucoma eyes, respectively. Cox proportional hazards regression analysis showed neovascular glaucoma as a risk factor for surgical failure (odds ratio, 5.384, 95% CI, 1.22–23.84, P = .027). Although IOP control and complications were comparable between the two groups, visual outcomes were worse in neovascular glaucoma patients, with 9 eyes (23.7%) with neovascular glaucoma compared with no controls losing light perception vision (P = .002). The majority with loss of vision (5 of 9) had successful control of IOP during the postoperative period. Conclusion: Neovascular glaucoma patients have greater risk of surgical failure after Ahmed glaucoma valve surgery compared with controls. Despite improved mean IOP with drainage implants, visual outcomes may be poor, possibly due to progression of underlying disease. PMID:20126506

  9. Primary lens extraction for glaucoma management: A review article

    PubMed Central

    Eid, Tarek M.

    2011-01-01

    Recently, primary lens extraction alone gained more acceptance as an alternative surgical approach for glaucoma management. This view was supported by the advances in phacoemulsification and intraocular lenses with greater safety and visual recovery, in addition to a substantial reduction of intraocular pressure and deepening of the anterior chamber and filtration angle. The decrease in IOP after cataract surgery in primary open-angle glaucoma (POAG) is mild, less predictable, related to baseline levels, and may return to presurgical values after an initial period of reduction. Therefore, the IOP-lowering effect of primary cataract extraction in POAG may be insufficient to achieve adequate IOP control. The IOP reduction after lens extraction is consistently greater in eyes with primary angle closure glaucoma (PACG) than in eyes with POAG. Primary lens extraction in acute PACG eliminates, or at least, reduces the risk of recurrence of acute attacks and deepens the anterior chamber and widens the angle which reduces the risk of progression of peripheral anterior synechiae and development of chronic PACG. Primary lens extraction may be more preferable to glaucoma incisional surgery in mild to moderate PACG eyes with appositional angle closure. The decision to do lens extraction as a primary treatment for glaucoma should be individualized based upon several factors other than the effect on IOP. These factors include patients’ characteristics, surgeons’ skills and preferences, status of glaucoma control, type of cataract and intraocular lens implanted, and potential harm of laser treatment for late capsular opacification and fibrosis. PMID:23960947

  10. Eye Conditions in Older Adults: Open-Angle Glaucoma.

    PubMed

    Iroku-Malize, Tochi; Kirsch, Scott

    2016-06-01

    Glaucoma is the leading cause of irreversible vision loss in the United States, affecting 1.9% of individuals older than 40 years. The prevalence of the most common form, open-angle glaucoma, increases with age and is higher in non-Hispanic minorities. The progressive loss of peripheral vision in glaucoma often leads to difficulty with driving, particularly at night, and can increase the risk of falls and subsequent fractures. Although glaucoma usually is characterized by chronically elevated intraocular pressure, it is more accurately defined as an optic neuropathy. Typically, there are no warning signs or symptoms, and extensive and permanent optic nerve damage can occur before the patient is aware of visual field loss. A cup to disc ratio greater than 0.6 on ophthalmoscopy is suspicious for glaucoma, and visual field testing results show a characteristic peripheral loss. Medical and surgical treatments are aimed at decreasing intraocular pressure by decreasing production of aqueous humor and increasing its outflow. Drugs for glaucoma treatment include prostaglandin analogs, beta blockers, alpha2-adrenergic agonists, and carbonic anhydrase inhibitors. Surgical or laser treatment is indicated if medical management is unsuccessful. Alternative therapies are less effective and have more adverse effects than standard treatments. PMID:27348527

  11. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Measurements of laser-induced shock waves in aluminium

    NASA Astrophysics Data System (ADS)

    Werdiger, M.; Arad, B.; Moshe, E.; Eliezer, S.

    1995-02-01

    A simple optical method for measurements of high-irradiance (3×1013 W cm-2) laser-induced shock waves is described. The shock wave velocity (~13 km s-1) was measured with an error not exceeding 5%. The laser-induced one-to-two-dimensional (1D-to-2D) shock wave transition was studied.

  12. Laser-Induced-Fluorescence Photogrammetry and Videogrammetry

    NASA Technical Reports Server (NTRS)

    Danehy, Paul; Jones, Tom; Connell, John; Belvin, Keith; Watson, Kent

    2004-01-01

    surface of the target. The improved method is denoted laser-induced-fluorescence photogrammetry.

  13. Advanced Imaging for Glaucoma Study: Design, Baseline Characteristics, and Inter-Site Comparison

    PubMed Central

    Le, Phuc V.; Zhang, Xinbo; Francis, Brian A.; Varma, Rohit; Greenfield, David S.; Schuman, Joel S.; Loewen, Nils; Huang, David

    2014-01-01

    Purpose To report the baseline characteristics of the participants in the Advanced Imaging for Glaucoma Study. To compare the participating sites for variations among subjects and the performance of imaging instruments. Design Multi-center longitudinal observational cohort study Methods A total of 788 participants (1,329 eyes) were enrolled from three academic referral centers. There were 145 participants (289 eyes) in the normal group, 394 participants (663 eyes) in the glaucoma suspect/preperimetric glaucoma group, and 249 participants (377 eyes) in the perimetric glaucoma group. Participants underwent a full clinical exam, standard automated perimetry, and imaging with time-domain and Fourier-domain optical coherence tomography (OCT), scanning laser polarimetry, and confocal scanning laser ophthalmoscopy. Main Outcome Measures The baseline average, population standard deviation, and repeatability of imaging-derived anatomic variables were reported for each technology and center. Results Compared to the normal participants, glaucoma suspect/preperimetric glaucoma and perimetric glaucoma groups had significantly reduced anatomic measurements. Repeatability of nerve fiber layer thickness was best for Fourier-domain OCT (overall coefficient of variation < 2%), followed by time-domain OCT (coefficient of variation 2-2.9%), scanning laser polarimetry (coefficient of variation 2.6-4.5%), and confocal scanning laser ophthalmoscopy rim area (coefficient of variation 4.2-7.6%). A mixed-effects model showed that the differences between sites was less than 25 percent of the variation within groups and less than the differences between the normal and glaucoma suspect/preperimetric glaucoma group. Conclusions Site-to-site variation was smaller than both the variation within groups and the changes due to glaucoma. Therefore pooling of participants between sites is appropriate. PMID:25447111

  14. The Role of the Immune System in Glaucoma: Bridging the Divide Between Immune Mechanisms in Experimental Glaucoma and the Human Disease.

    PubMed

    Kamat, Shivani S; Gregory, Meredith S; Pasquale, Louis R

    2016-01-01

    Glaucoma is one of the leading causes of visual impairment worldwide. Classically, clinicians have evaluated patients through a full ophthalmological examination including gonioscopy, measurement of intraocular pressure (IOP), and assessment of the optic nerve. New imaging modalities have further enhanced our ability to evaluate glaucoma; however, our treatments have not evolved as much. Whether one uses medical treatment with topical ocular antihypertensives, laser trabeculoplasty, or filtering surgery, the mainstay of treatment is to lower IOP. However, as our understanding of the disease evolves, mechanisms other than elevated IOP have been implicated in glaucoma pathogenesis. Recent animal model studies have shown a possible role of the immune system in the pathophysiology of glaucoma. This article explores the current understanding of immune reactions in glaucoma, which could lead to a new paradigm of treatment for human disease.

  15. Optical Coherence Tomography Angiography of Optic Disc Perfusion in Glaucoma

    PubMed Central

    Jia, Yali; Wei, Eric; Wang, Xiaogang; Zhang, Xinbo; Morrison, John C.; Parikh, Mansi; Lombardi, Lori H.; Gattey, Devin M.; Armour, Rebecca L.; Edmunds, Beth; Kraus, Martin F.; Fujimoto, James G.; Huang, David

    2014-01-01

    Purpose To compare optic disc perfusion between normal and glaucoma subjects using optical coherence tomography (OCT) angiography and detect optic disc perfusion changes in glaucoma. Design Observational, cross-sectional study. Participants Twenty-four normal subjects and 11 glaucoma patients were included. Methods One eye of each subject was scanned by a high-speed 1050 nm wavelength swept-source OCT instrument. The split-spectrum amplitude-decorrelation angiography algorithm (SSADA) was used to compute three-dimensional optic disc angiography. A disc flow index was computed from four registered scans. Confocal scanning laser ophthalmoscopy (cSLO) was used to measure disc rim area, and stereo photography was used to evaluate cup/disc ratios. Wide field OCT scans over the discs were used to measure retinal nerve fiber layer (NFL) thickness. Main Outcome Measurements Variability was assessed by coefficient of variation (CV). Diagnostic accuracy was assessed by sensitivity and specificity. Comparisons between glaucoma and normal groups were analyzed by Wilcoxon rank-sum test. Correlations between disc flow index, structural assessments, and visual field (VF) parameters were assessed by linear regression. Results In normal discs, a dense microvascular network was visible on OCT angiography. This network was visibly attenuated in glaucoma subjects. The intra-visit repeatability, inter-visit reproducibility, and normal population variability of the optic disc flow index were 1.2%, 4.2%, and 5.0% CV respectively. The disc flow index was reduced by 25% in the glaucoma group (p = 0.003). Sensitivity and specificity were both 100% using an optimized cutoff. The flow index was highly correlated with VF pattern standard deviation (R2 = 0.752, p = 0.001). These correlations were significant even after accounting for age, cup/disc area ratio, NFL, and rim area. Conclusions OCT angiography, generated by the new SSADA algorithm, repeatably measures optic disc perfusion. OCT

  16. OCT Imaging in Glaucoma

    NASA Astrophysics Data System (ADS)

    Nevins, Jessica E.; Wollstein, Gadi; Schuman, Joel S.

    The precise micron scale quantification of ocular structures provided by OCT turn this technology to be a valuable tool in clinical evaluation of glaucoma patients. This chapter describes the clinical utility of OCT from choosing the scan pattern and scan location to the interpretation of the test outcome.

  17. Laser induced incandescence and laser induced breakdown spectroscopy based sensor development

    NASA Astrophysics Data System (ADS)

    Eseller, Kemal Efe

    In this doctoral dissertation, two laser-based sensors were evaluated for different applications. Laser Induced Incandescence (LII) is a technique which can provide non-intrusive quantitative measurement of soot and it provides a unique diagnostic tool to characterize engine performance. Since LII is linearly proportional to the soot volume fraction, it can provide in situ, real time measurement of soot volume fraction with high temporal and spatial resolution. LII has the capability to characterize soot formation during combustion. The soot volume fraction from both flames and a soot generator was investigated with LII. The effects of experimental parameters, such as laser fluence, gate delay, gate width and various laser beam focusing, on LII signal was studied. Laser Induced Breakdown Spectroscopy (LIBS), a diagnostic tool for in situ elemental analysis, has been evaluated for on-line, simultaneous, multi-species impurity monitoring in hydrogen. LIBS spectra with different impurity levels of nitrogen, argon, and oxygen were recorded and the intensity of the spectral lines of Ar, O, N, and H observed were used to form calibration plots for impurities in hydrogen measurements. An ungated detection method for LIBS has been developed and applied to equivalence ratio measurements of CH4/air and biofuel/air. LIBS has also been used to quantitatively analyze the composition of a slurry sample. The quenching effect of water in slurry samples causes low LIBS signal quality with poor sensitivity. Univariate and multivariate calibration was performed on LIBS spectra of dried slurry samples for elemental analysis of Mg, Si and Fe. Calibration results show that the dried slurry samples give good correlation between spectral intensity and elemental concentration.

  18. Genetics Home Reference: early-onset glaucoma

    MedlinePlus

    ... Glaucoma Genetic Testing Registry (2 links) Glaucoma, congenital Primary open angle glaucoma juvenile onset 1 ClinicalTrials.gov (1 link) ClinicalTrials.gov Scientific articles on PubMed (1 link) PubMed OMIM (2 links) ...

  19. Glaucoma: Symptoms, Diagnosis, Treatment and Latest Research

    MedlinePlus

    ... of this page please turn Javascript on. Feature: Glaucoma Glaucoma: Symptoms, Diagnosis, Treatment and Latest Research Past Issues / Fall 2009 Table of Contents Symptoms and Diagnosis Glaucoma can develop in one or both eyes. Often ...

  20. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  1. Anterior chamber aqueous flare, pseudoexfoliation syndrome, and glaucoma.

    PubMed

    Kahloun, Rim; Attia, Sonia; Ksiaa, Imen; Kacem, Ilhem; Bouanene, Ines; Zaouali, Sonia; Jelliti, Bechir; Khairallah, Moncef

    2016-10-01

    The purpose of this study is to evaluate anterior chamber aqueous flare (ACAF) in Tunisian patients with pseudoexfoliation (PEX) syndrome with or without associated glaucoma. This is a prospective, cross-sectional, comparative study including 53 patients (88 eyes) with PEX syndrome, 48 patients with PEX glaucoma (86 eyes), and 53 healthy sex-and age-matched control subjects (106 eyes). All patients underwent a complete ophthalmic examination and laser flare photometry. Mean ACAF was significantly higher in the PEX syndrome group in comparison with the control group (17.96 ± 10.05 vs 7.06 ± 2.95 ph/ms; p = 10(-4)), in patients with PEX glaucoma compared to PEX syndrome without associated glaucoma (27.99 ± 15.45 vs 17.96 ± 10.05 ph/ms; p = 10(-4)), in the PEX glaucoma group in comparison with control group (27.99 ± 15.45 vs 7.06 ± 2.95 ph/ms; p = 10(-4)), and in patients with unilateral PEX syndrome in comparison with contralateral-unaffected eyes (25.72 ± 14.88 vs 8.58 ± 3.45 ph/ms; p = 0.000). For patients with PEX syndrome, a high ACAF might be a predictor for the development of glaucoma. Further investigations are needed to clarify the role of laser flare photometry in predicting the risk of glaucoma in patients with PEX syndrome. PMID:26787385

  2. Ahmed glaucoma valve surgery for necrotizing scleritis with secondary glaucoma.

    PubMed

    Ranjan, Abhishek; Rao, Aparna

    2014-04-01

    To report the challenges in management in a case of scleritis with extensive staphylomas with secondary glaucoma. A 35-year-old one eyed female, a known case of scleromalacia perforans, presented with raised intraocular pressure on maximum medical treatment. She underwent successful Ahmed glaucoma valve surgery with exposure of the implant following a repeat episode of necrotizing scleritis after 3 months. Management of eyes with scleritis and secondary glaucoma can be challenging with unexpected complications and postoperative course.

  3. Studies of new media radiation induced laser

    NASA Technical Reports Server (NTRS)

    Han, K. S.; Shiu, Y. J.; Raju, S. R.; Hwang, I. H.; Tabibi, B.

    1984-01-01

    Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed.

  4. Microwave interferometry of laser induced air plasmas formed by short laser pulses

    SciTech Connect

    Jungwirth, P.W.

    1993-08-01

    Applications for the interaction of laser induced plasmas with electromagnetic probes requires time varying complex conductivity data for specific laser/electromagnetic probe geometries. Applications for this data include plasma switching (Q switching) and the study of ionization fronts. The plasmas were created in laboratory air by 100 ps laser pulses at a wavelength of 1 {mu}m. A long focal length lens focused the laser pulse into WR90 (X band) rectangular waveguide. Two different laser beam/electromagnetic probe geometries were investigated. For the longitudinal geometry, the laser pulse and the microwave counterpropagated inside the waveguide. For the transverse geometry, the laser created a plasma ``post`` inside the waveguide. The effects of the laser beam deliberately hitting the waveguide were also investigated. Each geometry exhibits its own characteristics. This research project focused on the longitudinal geometry. Since the laser beam intensity varies inside the waveguide, the charge distribution inside the waveguide also varies. A 10 GHz CW microwave probe traveled through the laser induced plasma. From the magnitude and phase of the microwave probe, a spatially integrated complex conductivity was calculated. No measurements of the temporal or spatial variation of the laser induced plasma were made. For the ``plasma post,`` the electron density is more uniform.

  5. The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

    NASA Astrophysics Data System (ADS)

    Lindner, Helmut; Loper, Kristofer H.; Hahn, David W.; Niemax, Kay

    2011-02-01

    Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.

  6. A temperature-induced and shear-reversible assembly of latanoprost-loaded amphiphilic chitosan colloids: characterization and in vivo glaucoma treatment.

    PubMed

    Hsiao, Meng-Hsuan; Chiou, Shih-Hwa; Larsson, Mikael; Hung, Kuo-Hsuan; Wang, Yi-Ling; Liu, Catherine Jui-Ling; Liu, Dean-Mo

    2014-07-01

    Hydrogels composed of assembled colloids is a material class that is currently receiving much interest and shows great promise for use in biomedical applications. This emerging material class presents unique properties derived from the combination of nanosized domains in the form of colloidal particles with a continuous gel network and an interspersed liquid phase. Here we developed an amphiphilic chitosan-based, thermogelling, shear-reversible colloidal gel system for improved glaucoma treatment and addressed how preparation procedures and loading with the anti-glaucoma drug latanoprost and commonly used preservative benzalkonium chloride influenced the mechanical properties of and drug release from the colloidal gels. The results highlight that incorporated substances and preparation procedures have effects both on mechanical properties and drug release, but that the release of drug loaded in the colloidal carriers is mainly limited by transport out of the carriers, rather than by diffusion within the gel. The developed colloidal chitosan based gels hold outstanding biomedical potential, as confirmed by the ease of preparation and administration, low cytotoxicity in MTT assay, excellent biocompatibility and lowering of intraocular pressure for 40 days in a rabbit glaucoma model. The findings clearly justify further investigations towards clinical use in the treatment of glaucoma. Furthermore, the use of this shear-reversible colloidal gel could easily be extended to localized treatment of a number of critical conditions, from chronic disorders to cancer, potentially resulting in a number of new therapeutics with improved clinical performance.

  7. Picosecond laser-induced water condensation in a cloud chamber.

    PubMed

    Sun, Haiyi; Liu, Yonghong; Ju, Jingjing; Tian, Ye; Bai, Yafeng; Liu, Yaoxiang; Du, Shengzhe; Wang, Cheng; Wang, Tiejun; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2016-09-01

    We investigated water condensation in a laboratory cloud chamber induced by picosecond (ps) laser pulses at ~350 ps (800 nm/1-1000 Hz) with a maximum peak power of ~25 MW. The peak power was much lower than the critical power for self-focusing in air (~3-10 GW depending on the pulse duration). Sparks, airflow and snow formation were observed under different laser energies or repetition rates. It was found that weaker ps laser pulses can also induce water condensation by exploding and breaking down ice crystals and/or water droplets into tiny particles although there was no formation of laser filament. These tiny particles would grow until precipitation in a super-saturation zone due to laser-induced airflow in a cold region with a large temperature gradient.

  8. Picosecond laser-induced water condensation in a cloud chamber.

    PubMed

    Sun, Haiyi; Liu, Yonghong; Ju, Jingjing; Tian, Ye; Bai, Yafeng; Liu, Yaoxiang; Du, Shengzhe; Wang, Cheng; Wang, Tiejun; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2016-09-01

    We investigated water condensation in a laboratory cloud chamber induced by picosecond (ps) laser pulses at ~350 ps (800 nm/1-1000 Hz) with a maximum peak power of ~25 MW. The peak power was much lower than the critical power for self-focusing in air (~3-10 GW depending on the pulse duration). Sparks, airflow and snow formation were observed under different laser energies or repetition rates. It was found that weaker ps laser pulses can also induce water condensation by exploding and breaking down ice crystals and/or water droplets into tiny particles although there was no formation of laser filament. These tiny particles would grow until precipitation in a super-saturation zone due to laser-induced airflow in a cold region with a large temperature gradient. PMID:27607654

  9. Coherent microwave radiation from a laser induced plasma

    SciTech Connect

    Shneider, M. N.; Miles, R. B.

    2012-12-24

    We propose a method for generation of coherent monochromatic microwave/terahertz radiation from a laser-induced plasma. It is shown that small-scale plasma, located in the interaction region of two co-propagating plane-polarized laser beams, can be a source of the dipole radiation at a frequency equal to the difference between the frequencies of the lasers. This radiation is coherent and appears as a result of the so-called optical mixing in plasma.

  10. Q-Switched Alexandrite Laser-induced Chrysiasis

    PubMed Central

    Victor Ross, E.

    2015-01-01

    Background: Chyriasis is an uncommon side effect that occurs in patients who are receiving prolonged treatment with either intravenous or intramuscular gold as a distinctive blue-gray pigmentation of light-exposed skin. Laser-induced chrysiasis is a rarely described phenomenon in individuals who have received systemic gold and are subsequently treated with a Q-switched laser. Purpose: To describe the characteristics of patients with laser-induced chrysiasis. Methods: The authors describe a 60-year-old woman who developed chrysiasis at Q-switched alexandrite laser treatment sites. They also reviewed the medical literature using PubMed, searching the terms chrysiasis, gold, and laser-induced. Patient reports and previous reviews of these subjects were critically assessed and the salient features are presented. Results: Including the authors’ patient, laser-induced chrysiasis has been described in five Caucasian arthritis patients (4 women and 1 man); most of the patients had received more than 8g of systemic gold therapy during a period of 3 to 13 years. Gold therapy was still occurring or had been discontinued as long as 26 years prior to laser treatment. All of the patients immediately developed blue macules at the Q-switched laser treatment site. Resolution of the dyschromia occurred in a 70-year-old woman after two treatment sessions with a long-pulsed ruby laser and the authors’ patient after a sequential series of laser sessions using a long-pulsed alexandrite laser, followed by a nonablative fractional laser and an ablative carbon dioxide laser. Conclusion: Laser-induced chrysiasis has been observed following treatment with Q-switched lasers in patients who are receiving or have previously been treated with systemic gold. It can occur decades after treatment with gold has been discontinued. Therefore, inquiry regarding a prior history of treatment with gold—particularly in older patients with arthritis—should be considered prior to treatment with a Q

  11. [The Spectral Analysis of Laser-Induced Plasma in Laser Welding with Various Protecting Conditions].

    PubMed

    Du, Xiao; Yang, Li-jun; Liu, Tong; Jiao, Jiao; Wang, Hui-chao

    2016-01-01

    The shielding gas plays an important role in the laser welding process and the variation of the protecting conditions has an obvious effect on the welding quality. This paper studied the influence of the change of protecting conditions on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process by designing some experiments of reducing the shielding gas flow rate step by step and simulating the adverse conditions possibly occurring in the actual Nd : YAG laser welding process. The laser-induced plasma was detected by a fiber spectrometer to get the spectral data. So the electron temperature of laser-induced plasma was calculated by using the method of relative spectral intensity and the electron density by the Stark Broadening. The results indicated that the variation of protecting conditions had an important effect on the electron temperature and the electron density in the laser welding. When the protecting conditions were changed, the average electron temperature and the average electron density of the laser-induced plasma would change, so did their fluctuation range. When the weld was in a good protecting condition, the electron temperature, the electron density and their fluctuation were all low. Otherwise, the values would be high. These characteristics would have contribution to monitoring the process of laser welding. PMID:27228732

  12. Glaucoma Management in Carotid Cavernous Fistula

    PubMed Central

    Calafiore, Silvia; Perdicchi, Andrea; Scuderi, Gianluca; Contestabile, Maria Teresa; Abdolrahimzadeh, Solmaz; Recupero, Santi Maria

    2016-01-01

    Carotid cavernous fistulas (CCF) are vascular communications between the carotid artery and the cavernous sinus. Ophthalmologists are called to diagnose and manage the condition in cases that present with ocular features. A 73-year-old female was referred to our glaucoma center clinic. Eight years before, she had started receiving medication for glaucoma and had undergone laser iridotomy, but a satisfactory management of intraocular pressure (IOP) had not been achieved. The patient was complaining of intermittent diplopia, bilateral proptosis, and conjunctival chemosis over the past 6 months. Best-corrected visual acuity in the right (OD) and left eye (OS) was 9/10 and 10/10, respectively. Visual field testing showed slight paracentral field defects mostly in OS. IOP was 20 mm Hg in OD and 34 mm Hg in OS. We referred the patient to neuroradiology, and MRI angiography revealed a CCF with angiographic classification of Cognard grade 2. Closure of the CCF by transarterial embolization was performed in the neuroradiology department. One week following the procedure, the clinical signs of diplopia, proptosis, and conjunctival chemosis had greatly improved, and IOP was reduced to 12 mm Hg OD and 19 mm Hg in OS. Glaucoma treatment was maintained with topical brimatoprost, brinzolamide, and timolol. Owing to the risk of vision loss associated with vascular stasis, retinal ischemia, and high IOP, ophthalmologists must be aware of the clinical features of CCF and should request appropriate imaging studies such as MRI angiography in order to confirm the diagnosis and plan multidisciplinary treatment. PMID:27462258

  13. Glaucoma Management in Carotid Cavernous Fistula.

    PubMed

    Calafiore, Silvia; Perdicchi, Andrea; Scuderi, Gianluca; Contestabile, Maria Teresa; Abdolrahimzadeh, Solmaz; Recupero, Santi Maria

    2016-01-01

    Carotid cavernous fistulas (CCF) are vascular communications between the carotid artery and the cavernous sinus. Ophthalmologists are called to diagnose and manage the condition in cases that present with ocular features. A 73-year-old female was referred to our glaucoma center clinic. Eight years before, she had started receiving medication for glaucoma and had undergone laser iridotomy, but a satisfactory management of intraocular pressure (IOP) had not been achieved. The patient was complaining of intermittent diplopia, bilateral proptosis, and conjunctival chemosis over the past 6 months. Best-corrected visual acuity in the right (OD) and left eye (OS) was 9/10 and 10/10, respectively. Visual field testing showed slight paracentral field defects mostly in OS. IOP was 20 mm Hg in OD and 34 mm Hg in OS. We referred the patient to neuroradiology, and MRI angiography revealed a CCF with angiographic classification of Cognard grade 2. Closure of the CCF by transarterial embolization was performed in the neuroradiology department. One week following the procedure, the clinical signs of diplopia, proptosis, and conjunctival chemosis had greatly improved, and IOP was reduced to 12 mm Hg OD and 19 mm Hg in OS. Glaucoma treatment was maintained with topical brimatoprost, brinzolamide, and timolol. Owing to the risk of vision loss associated with vascular stasis, retinal ischemia, and high IOP, ophthalmologists must be aware of the clinical features of CCF and should request appropriate imaging studies such as MRI angiography in order to confirm the diagnosis and plan multidisciplinary treatment. PMID:27462258

  14. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Haisu; Tzortzakis, Stelios

    2016-05-01

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  15. IR laser-induced protein crystal transformation.

    PubMed

    Kiefersauer, Reiner; Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-05-01

    A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress.

  16. IR laser-induced protein crystal transformation

    SciTech Connect

    Kiefersauer, Reiner Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-05-01

    A novel method and the associated instrumentation for improving crystalline order (higher resolution of X-ray diffraction and reduced mosaicity) of protein crystals by precisely controlled heating is demonstrated. Crystal transformation is optically controlled by a video system. A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress.

  17. Medical Applications of Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pathak, A. K.; Rai, N. K.; Singh, Ankita; Rai, A. K.; Rai, Pradeep K.; Rai, Pramod K.

    2014-11-01

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

  18. Anions in laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Shabanov, S. V.; Gornushkin, I. B.

    2016-07-01

    The equation of state for plasmas containing negative atomic and molecular ions (anions) is modeled. The model is based on the assumption that all ionization processes and chemical reactions are at local thermal equilibrium and the Coulomb interaction in the plasma is described by the Debye-Hückel theory. In particular, the equation of state is obtained for plasmas containing the elements Ca, Cl, C, Si, N, and Ar. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules CaCl_2, CaCl, Cl_2, N_2, C_2, Si_2, CN, SiN, SiC, and their positive and negative ions. The model is applied to laser-induced plasmas (LIPs) by including the equation of state into a fluid dynamic numerical model based on the Navier-Stokes equations describing an expansion of LIP plumes into an ambient gas as a reactive viscous flow with radiative losses. In particular, the formation of anions Cl-, C-, Si-, {{Cl}}2^{ - }, {{Si}}2^{ - }, {{C}}2^{ - }, CN-, SiC-, and SiN- in LIPs is investigated in detail.

  19. Improved Imaging With Laser-Induced Eddy Currents

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    System tests specimen of material nondestructively by laser-induced eddy-current imaging improved by changing method of processing of eddy-current signal. Changes in impedance of eddy-current coil measured in absolute instead of relative units.

  20. Classical cutoffs for laser-induced nonsequential double ionization

    SciTech Connect

    Milosevic, D.B.; Becker, W.

    2003-12-01

    Classical cutoffs for the momenta of electrons ejected in laser-induced nonsequential double ionization are derived for the recollision-impact-ionization scenario. Such simple cutoff laws can aid in the interpretation of the observed electron spectra.

  1. MEMS glaucoma monitoring device

    NASA Astrophysics Data System (ADS)

    Shankar, Smitha; Austin, Michael

    2007-04-01

    Glaucoma is a serious disease, affecting millions of people worldwide requiring continuous monitoring of Intra Ocular Pressure (IOP) to avoid the risk of blindness. Current laboratory measurements are infrequent, intrusive and do not indicate the progression of the disease. The paper reports on the development of an implantable Glaucoma monitoring system that can monitor IOP in the eye to indicate any elevation in risk to the patient. A mathematical model of the anterior chamber of the eye was used to analyze the complex fluid flow and pressure balance in the eye. This was done in order to determine the performance requirements of the actuator, sensor and transmission electronics that could be integrated on a single microchip using microelectromechanical systems (MEMS) technology, to carry out the testing internally. The accuracy of the system was theoretically tested against results from external medical tests. The results were found to be comparable.

  2. Endothelin, Astrocytes and Glaucoma

    PubMed Central

    Prasanna, Ganesh; Krishnamoorthy, Raghu; Yorio, Thomas

    2010-01-01

    It has become increasingly clear that astrocytes may play an important role in the genesis of glaucoma. Astrogliosis occurs in response to ocular stress or the presence of noxious stimuli. Agents that appear to stimulate reactive gliosis are becoming increasingly clear. One class of agents that is emerging is the endothelins (ETs; specifically, ET-1). In this review we examine the interactions of ET-1 with astrocytes and provide examples where ET-1 appears to contribute to activation of astrocytes and play a role in the neurodegenerative effects that accompany such reactivation resulting in astrogliosis. These actions are presented in the context of glaucoma although information is also presented with respect to ET-1's role in the central nervous system and brain. While much has been learned with respect to ET-1/astrocyte interactions, there are still a number of questions concerning the potential therapeutic implications of these findings. Hopefully this review will stimulate others to examine this potential. PMID:20849847

  3. Microbead models in glaucoma.

    PubMed

    Morgan, James E; Tribble, James R

    2015-12-01

    The sustained and moderate elevation of intraocular pressure, which can be initiated at precise time points, remains the cornerstone of research into the mechanisms of glaucomatous retinal damage. We focus on the use of microbeads to block the outflow of aqueous following anterior chamber injection in a range of animals (mouse, rat and primate). We describe some of the most commonly used parameters and present guidance on injection technique and bead manipulation to facilitate the successful generation of experimental glaucoma.

  4. Laser-induced thermal acoustic velocimetry

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan

    2000-11-01

    Laser-Induced Thermal Acoustics (LITA) is a non- intrusive, remote, four-wave mixing laser diagnostic technique for measurements of the speed of sound and of the thermal diffusivity in gases. If the gas composition is known, then its temperature and density can be inferred. Beam misalignments and bulk fluid velocities can influence the time history and intensity of LITA signals. A closed-form analytic expression for LITA signals incorporating these effects is derived. The magnitude of beam misalignment and the flow velocity can be inferred from the signal shape using a least-squares fit of this model to the experimental data. High-speed velocimetry using homodyne detection is demonstrated with NO2-seeded air in a supersonic blow-down nozzle. The measured speed of sound deviates less than 2% from the theoretical value assuming isentropic quasi-1D flow. Boundary layer effects degrade the velocity measurements to errors of 20%. Heterodyne detection is used for low-speed velocimetry up to Mach number M = 0.1. The uncertainty of the velocity measurements was ~0.2 m/s. The sound speed measurements were repeatable to 0.5%. The agreement between theory and experiments is very good. A one-hidden-layer feed-forward neural network is trained using back-propagation learning and a steepest descent learning rule to extract the speed of sound and flow velocity from a heterodyne LITA signal. The effect of the network size on the performance is demonstrated. The accuracy is determined with a second set of LITA signals that were not used during the training phase. The accuracy is found to be better than that of a conventional frequency decomposition technique while being computationally as efficient. This data analysis method is robust with respect to noise, numerically stable, and fast enough for real-time data analysis. The accuracy and uncertainty of non-resonant LITA measurements is investigated. The error in measurements of the speed of sound and of the thermal diffusivity

  5. Treatment outcomes of micropulse transscleral cyclophotocoagulation in advanced glaucoma.

    PubMed

    Kuchar, Sarah; Moster, Marlene R; Reamer, Courtney B; Waisbourd, Michael

    2016-02-01

    Glaucoma is the leading cause of irreversible blindness worldwide. The goal of this study was to describe our experience with the novel micropulse transscleral cyclophotocoagulation (MP-TSCPC; IRIDEX IQ810 Laser Systems, CA) in patients with advanced glaucoma. Patients with advanced glaucoma who underwent MP-TSCPC were included in our study. Laser settings were 2000 mW of 810 nm infrared diode laser set on micropulse delivery mode. The laser was delivered over 360° for 100-240 s. The duty cycle was 31.3 %, which translated to 0.5 ms of "on time" and 1.1 ms of "off time." Surgical success was defined as an intraocular pressure (IOP) of 6-21 mmHg or a reduction of IOP by 20 % at the last follow-up visit. Failure was defined as an inability to meet the criteria for success or a need for incisional glaucoma surgery. Nineteen patients underwent MP-TSCPC with mean follow-up of 60.3 days. Mean IOP dropped from 37.9 mmHg preoperatively to 22.7 mmHg at last follow-up, representing a 40.1 % decrease. The success rate for initial treatment was 73.7 % (n = 14). Three patients underwent a second treatment, increasing the overall success rate to 89.5 % (n = 17). Four patients gained one line of vision, and four patients lost one line of vision. The novel MP-TSCPC laser had a high rate of surgical success after a short follow-up period in patients with advanced glaucoma. Further long-term evaluation and comparison to the traditional transscleral cyclophotocoagulation are warranted.

  6. Treatment outcomes of micropulse transscleral cyclophotocoagulation in advanced glaucoma.

    PubMed

    Kuchar, Sarah; Moster, Marlene R; Reamer, Courtney B; Waisbourd, Michael

    2016-02-01

    Glaucoma is the leading cause of irreversible blindness worldwide. The goal of this study was to describe our experience with the novel micropulse transscleral cyclophotocoagulation (MP-TSCPC; IRIDEX IQ810 Laser Systems, CA) in patients with advanced glaucoma. Patients with advanced glaucoma who underwent MP-TSCPC were included in our study. Laser settings were 2000 mW of 810 nm infrared diode laser set on micropulse delivery mode. The laser was delivered over 360° for 100-240 s. The duty cycle was 31.3 %, which translated to 0.5 ms of "on time" and 1.1 ms of "off time." Surgical success was defined as an intraocular pressure (IOP) of 6-21 mmHg or a reduction of IOP by 20 % at the last follow-up visit. Failure was defined as an inability to meet the criteria for success or a need for incisional glaucoma surgery. Nineteen patients underwent MP-TSCPC with mean follow-up of 60.3 days. Mean IOP dropped from 37.9 mmHg preoperatively to 22.7 mmHg at last follow-up, representing a 40.1 % decrease. The success rate for initial treatment was 73.7 % (n = 14). Three patients underwent a second treatment, increasing the overall success rate to 89.5 % (n = 17). Four patients gained one line of vision, and four patients lost one line of vision. The novel MP-TSCPC laser had a high rate of surgical success after a short follow-up period in patients with advanced glaucoma. Further long-term evaluation and comparison to the traditional transscleral cyclophotocoagulation are warranted. PMID:26714976

  7. Laser induced decohesion of coatings: probing by laser ultrasonics.

    PubMed

    Rosa, G; Oltra, R; Nadal, M H

    2002-05-01

    The aim of the present study is to investigate a conventional laser-ultrasonics technique for the determination of intrinsic properties of oxide coatings and their adhesion strength on a metallic substrate. The good agreement between experiments and computations in an epicenter configuration allows determining the longitudinal wave velocity as well as the Young's modulus of the oxide coatings versus the porosity. For a critical value of the laser energy, a breakdown at the coating-substrate interface is generated by the laser irradiation. The critical tensile stress field developed at the coating/substrate interface, which leads to the interfacial fracture, can be easily calculated. The value of the practical adhesion which is defined is found to be in accordance with those obtained by classic contact techniques (tensile adhesion test, indentation, bending test). Finally, this work demonstrates that this quantitative, contactless test fits well to simultaneously characterise the oxide coatings and evaluate the coating-substrate adhesion. PMID:12160041

  8. Remote sensing of phytoplankton using laser-induced fluorescence

    SciTech Connect

    Babichenko, S.; Poryvkina, L.; Arikese, V. ); Kaitala, S. ); Kuosa, H. )

    1993-06-01

    The results of remote laser sensing of brackish-water phytoplankton on board a research vessel are presented. Field data of laser-induced fluorescence of phytoplankton obtained during the several cruises in the mouth of tile Gulf of Finland are compared with the results of standard chlorophyll a analysis of water samples and phytoplankton species determination by microscopy. The approach of fluorescence excitation by tunable laser radiation is applied to study the spatial distribution of a natural phytoplankton community. The remote analysis of the pigment composition of a phytoplankton community using the method of selective pigment excitation is described. The possibility of elaborating methods of quantitative laser remote biomonitoring is discussed.

  9. Laser induced modification and ablation of InAs nanowires

    SciTech Connect

    He Jiayu; Chen Pingping; Lu Wei; Dai Ning; Zhu Daming

    2012-05-01

    InAs nanowires were irradiated locally under an ambient condition using a focused laser beam, which led to laser ablation and thinning of the nanowires. We show that the laser beam can induce a reduction of the local As concentration in an InAs nanowire; the change leads to a significant decrease of local melting temperature of InAs, which results in the thinning and eventually breaking of the nanowire. The results indicate that chemical and mechanical modifications of an InAs nanowire can be accomplished by using a confocal laser beam, which may prove to be a convenient approach in fabricating nanostructural materials and nanodevices.

  10. Expansion of radiative cooling of the laser induced plasma

    SciTech Connect

    Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph; Russo,Richard

    2006-05-05

    To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.

  11. Influence of organic contamination on laser induced damage of multilayer dielectric mirrors by subpicosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Favrat, O.; Sozet, M.; Tovena-Pécault, I.; Lamaignère, L.; Néauport, J.

    2014-10-01

    Laser induced damage of optical components is often a limiting factor for the development of high power lasers. Indeed, for many years, organic contamination is identified as a factor decreasing the laser induced damage threshold of optical surfaces, limiting the use of high fluencies. Also, for the development of its laser facilities, Laser MégaJoule and PETawatt Aquitaine Laser, the Commissariat à l'Energie Atomique et aux Energies Alternatives investigates the influence of organic contamination on the performances of the optical components. Actually, although great care is provided on the cleanliness of the optics, organic volatile compounds outgassed from surrounding materials can be adsorbed by the sensitive surfaces during its timelife. Thus, for this study, performances of clean and contaminated multilayer dielectric mirrors are compared. Contamination is intentionally realized either by controlled protocols or by exposing optics inside the laser facilities. Qualification and quantification of the organic contamination is realized by automated thermal desorption and gas chromatography coupled with mass spectrometry. Laser induced damage threshold of clean and contaminated mirrors are then investigated by 1053 nm laser at 670 fs.

  12. Dynamical behavior of laser-induced nanoparticles during remote processing

    NASA Astrophysics Data System (ADS)

    Scholz, Tobias; Dickmann, Klaus; Ostendorf, Andreas

    2014-02-01

    Laser remote processing is used in a wide field of industrial applications. Among other things, it is characterized by flexible beam guidance in combination with high processing velocities. But in most cases process gas support in the interaction zone is omitted. Consequently, interaction mechanism between the vapor plume and the incident laser radiation can dynamically affect the process stability. Referring to remote welding with high brilliant laser sources having a wavelength around 1 μm, the interaction between the incident laser radiation and formed particles plays an important role. The presented work shows results of the investigation of the laser-induced particle formation during the laser welding of stainless steel with a 2 kW fiber laser under remote conditions. It is therefore concentrated on the dynamical behavior of the laser-induced particle formation and the dependence of the particle formation on the laser beam power. TEM images of formed particles were analyzed. In addition, the radiation of a LED was directed through the vapor plume. On the one hand, the dynamic of the attenuation was considered. On the other hand, the Rayleigh approximation was used in order to evaluate the detected signals.

  13. Laser inducement of Agricus bisporus I

    NASA Astrophysics Data System (ADS)

    Mao, Ning; Chen, Rong; Wang, Zesheng

    1996-09-01

    Using different power, different dosage's He-Ne laser (632.8 nm) and semiconductor laser (805 nm) to irradiated mycelia of four Agricus bisporus strains. And using no irradiate strain as contrast. Picking out some mycelium from irradiation position and then transfer them into Potato Dextrose Agar culture medium, culturing 12 - 15 days. We use the polyacrylamide slab gel electrophoresis to examine the esterase (EST) isozymes of mycelium. We could find from the result that laser irradiating could not change the Rf of main bands (F&s zones) of mycelium EST. However, 20 mw He- Ne, 10 minutes irradiation could not only raise the activity of EST distinctly, but also increase the numbers of enzyme zone of M zone, the difference between the semiconductor irradiation of 140 mv, 10 minutes and 20 mv, 10 minutes are not remarkable. And the irradiating effect of He-Ne laser is better than that of semiconductor laser.

  14. [Case with postoperative acute angle-closure glaucoma].

    PubMed

    Mihara, Ryosuke; Tanaka, Motoshige; Nakahira, Junko; Fujitate, Yasutaka; Minami, Toshiaki

    2011-08-01

    A 59-year-old man who had undergone biopsy of cervical lymph node under general anesthesia developed an attack of acute angle-closure glaucoma the night after the surgery. He had had no eye symptoms before. He complained of visual disorder, nausea, eye pain, and dizziness after the surgery. His intraocular pressure in the right eye was high (69 mmHg), and an ophthalmologist diagnosed it as acute angle-closure glaucoma. Dropping lotion in the eyes and the intravenous administration were not effective. His intraocular pressure decreased immediatery after laser iridotomy, and his symptoms improved. When the symptoms of eye pain and visual impairment appeared after the surgery, we should take acute angle-closure glaucoma into consideration and treat it as soon as possible.

  15. [Micro-invasive glaucoma surgery].

    PubMed

    Achiron, Asaf; Sharif, Nardeen; Achiron, Romi Noy; Nisimov, Sagee; Burgansky-Eliash, Sagee

    2014-10-01

    Intraocular pressure (IOP) reduction is the current treatment in glaucoma. In recent years, minimally invasive glaucoma surgery (MIGS) has been added to the arsenal of surgical options. MIGS can reduce trabecular meshwork resistance to outflow and decrease the IOP with mild side effects. In this article, we review the clinical experience gathered with iSTENT, Bypass, Gold Micro Shunt and the Trabectome.

  16. Crystal structure of laser-induced subsurface modifications in Si

    DOE PAGES

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in ’t Veld, A. J.

    2015-06-04

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this paper, we investigate the geometry and crystalmore » structure of laser-induced subsurface modifications in monocrystalline silicon wafers. Finally, in addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiation.« less

  17. Crystal structure of laser-induced subsurface modifications in Si

    SciTech Connect

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in ’t Veld, A. J.

    2015-06-04

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this paper, we investigate the geometry and crystal structure of laser-induced subsurface modifications in monocrystalline silicon wafers. Finally, in addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiation.

  18. Time-resolved aluminium laser-induced plasma temperature measurements

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2014-11-01

    We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 ± 270 to 3862 ± 46 Kelvin from 10 to 100 μs time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened Hβ spectra.

  19. Current Surgical Options for the Management of Pediatric Glaucoma

    PubMed Central

    Morales, Jose; Al Shahwan, Sami; Al Odhayb, Sami; Al Jadaan, Ibrahim; Edward, Deepak P.

    2013-01-01

    Currently, there are numerous choices for the treatment of pediatric glaucoma depending on the type of glaucoma, the age of the patient, and other particularities of the condition discussed in this review. Traditionally, goniotomy and trabeculotomy ab externo have been the preferred choices of treatment for congenital glaucoma, and a variety of adult procedures adapted to children have been utilized for other types of pediatric glaucoma with variable results and complications. More recently, seton implantations of different types have become more popular to use in children, and newer techniques have become available including visualized cannulation and opening of Schlemm's canal, deep sclerectomy, trabectome, and milder more directed cyclodestructive procedures such as endolaser and transcleral diode laser cyclophotocoagulation. This paper reviews the different surgical techniques currently available, their indications, results, and most common complications to allow the surgeon treating these conditions to make a more informed choice in each particular case. Although the outcome of surgical treatment in pediatric glaucoma has improved significantly, its treatment remains challenging. PMID:23738051

  20. New directions in the treatment of normal tension glaucoma.

    PubMed

    Song, Brian J; Caprioli, Joseph

    2014-05-01

    Glaucoma is a progressive optic neuropathy that causes characteristic changes of the optic nerve and visual field in relation to intraocular pressure (IOP). It is now known that glaucoma can occur at statistically normal IOPs and prevalence studies have shown that normal tension glaucoma (NTG) is more common than previously thought. While IOP is believed to be the predominant risk factor in primary open angle glaucoma (POAG), IOP-independent risk factors, such as vascular dysregulation, are believed to play an important part in the pathogenesis of NTG. Though certain distinguishing phenotypic features of NTG have been reported, such as an increased frequency of disc hemorrhages, acquired pits of the optic nerve and characteristic patterns of disc cupping and visual field loss, there is much overlap of the clinical findings in NTG with POAG, suggesting that NTG is likely part of a continuum of open angle glaucomas. However, IOP modification is still the mainstay of treatment in NTG. As in traditional POAG, reduction of IOP can be achieved with the use of medications, laser trabeculoplasty or surgery. Studies now show that the choice of medication may also be important in determining the outcomes of these patients. Though it is likely that future treatment of NTG will involve modification of both IOP and IOP-independent risk factors, current efforts to develop IOP-independent neuroprotective treatments have not yet proven to be effective in humans. PMID:24881596

  1. Laser Trabeculoplasty Induces Changes in the Trabecular Meshwork Glycoproteome: A pilot study

    PubMed Central

    Amelinckx, Adriana; Castello, Maria; Arrieta-Quintero, Esdras; Lee, Tinthu; Salas, Nelson; Hernandez, Eleut; Lee, Richard K.; Bhattacharya, Sanjoy K.; Parel, Jean-Marie A

    2009-01-01

    Laser trabeculoplasty (LT) is a commonly used modality of treatment for glaucoma. The mechanism by which LT lowers the intraocular pressure (IOP) is unknown. Using cat eyes, selective laser trabeculoplasty (SLT) with a Q-switched frequency doubled Nd:YAG laser was used to treat the trabecular meshwork (TM). Laser treated TM was then subjected to proteomic analysis for detection of molecular changes and histological analysis for the detection of structural and protein expression patterns. In addition, the protein glycosylation patterns of laser treated and non-treated TM was assessed and differentially glycosylated proteins were proteomically identified. SLT laser treatment to the TM resulted in elevated glycosylation levels compared to non-lasered TM. TM laser treatment also resulted in protein expression levels changes of several proteins. Elevated levels of biglycan, keratocan and prolargin were detected in laser treated TM compared to non-lasered controls. Further investigation is anticipated to provide insight into how glycosylation changes affect TM proteins and TM regulation of aqueous outflow in response to laser trabeculoplasty. PMID:19432485

  2. Neurodegeneration and Neuroprotection in Glaucoma.

    PubMed

    Gauthier, Angela C; Liu, Ji

    2016-03-01

    Glaucoma is the principal cause of irreversible blindness in the world. The disease leads to progressive optic nerve degeneration with a gradual loss of retinal ganglion cells. Neurodegeneration in glaucoma extends beyond the eye into the lateral geniculate nucleus and visual cortex, and the disease even shares some characteristics with other central nervous system degenerative disorders. Glaucoma destroys neurons through oxidative stress, impairment in axonal transport, neuroinflammation, and excitotoxicity. Autophagy may promote or inhibit disease progression. Currently, lowering intraocular pressure is the only way proven to delay glaucoma advancement. However, many new therapies are being developed, including antioxidants, adenosine receptor antagonists, Rho-pathway inhibitors, stem cell therapy, and neurotrophic factors. These therapies focus on neuroprotection, and they may eventually halt glaucoma progression or reverse the process of the disease itself. PMID:27505018

  3. The Future of Glaucoma Surgery.

    PubMed

    Sheybani, Arsham

    2015-01-01

    Glaucoma surgery is ripe for innovation. In the last few years, there has been a substantial increase in the number of devices approaching commercialization. While not all that is new is necessarily good, the role of these devices in changing glaucoma surgery is equally important in terms of both success and failure. Trabeculectomy, the most commonly performed incisional filtration surgery for glaucoma, is subjective by nature and certainly has risks. As devices aim to standardize glaucoma surgery, specifically subconjunctival filtration surgery, predictability and in turn safety should theoretically improve. This may allow the glaucoma surgeon to intervene earlier in the disease process, prevent more advanced vision loss and potentially decrease the burden of medications.

  4. Neurodegeneration and Neuroprotection in Glaucoma

    PubMed Central

    Gauthier, Angela C.; Liu, Ji

    2016-01-01

    Glaucoma is the principal cause of irreversible blindness in the world. The disease leads to progressive optic nerve degeneration with a gradual loss of retinal ganglion cells. Neurodegeneration in glaucoma extends beyond the eye into the lateral geniculate nucleus and visual cortex, and the disease even shares some characteristics with other central nervous system degenerative disorders. Glaucoma destroys neurons through oxidative stress, impairment in axonal transport, neuroinflammation, and excitotoxicity. Autophagy may promote or inhibit disease progression. Currently, lowering intraocular pressure is the only way proven to delay glaucoma advancement. However, many new therapies are being developed, including antioxidants, adenosine receptor antagonists, Rho-pathway inhibitors, stem cell therapy, and neurotrophic factors. These therapies focus on neuroprotection, and they may eventually halt glaucoma progression or reverse the process of the disease itself. PMID:27505018

  5. Two-dimensional Temperature Measurement in Laser-induced Breakdown (LIB) using Planar Laser-induced Fluorescence (PLIF)

    NASA Astrophysics Data System (ADS)

    Chen, Ying-Ling; Parigger, Christian; Plemmons, David H.; Lewis, J. W. L.

    1996-05-01

    Two-dimensional temperature maps of the spatial profile of NH have been obtained following laser-induced breakdown of NH_3. A focused Nd:YAG laser of nominally 30 mJ and 6 ns pulsewidth was used to obtain laser breakdown of atmospheric pressure, flowing gaseous NH_3. The recombination NH A-X far-ultraviolet spectra was studied over the temporal region of 1 - 100 μs following breakdown. Spontaneous emission and planar laser-induced fluorescence (PLIF) spectra were observed using a two dimensional image-intensifier filter combination. The PLIF excitation spetra were achieved using an excimer-pumped dye laser, and temperature were obtained using Boltzmann plots. The results show the spatial profiles of the remnant plasma kernel and the effect of gas-dynamic expansion.

  6. Complications of selective laser trabeculoplasty: a review

    PubMed Central

    Song, Julia

    2016-01-01

    Selective laser trabeculoplasty is a laser treatment to treat glaucoma. It was initially indicated for open-angle glaucoma but has been proven to be efficacious for various types of glaucoma. This review article summarizes the few rare complications that can be seen with selective laser trabeculoplasty. It also makes recommendations on how to avoid these problems and how to treat patients when these rare complications arise. PMID:26834456

  7. Laser-induced periodic annular surface structures on fused silica surface

    SciTech Connect

    Liu, Yi; Brelet, Yohann; Forestier, Benjamin; Houard, Aurelien; Yu, Linwei; Deng, Yongkai; Jiang, Hongbing

    2013-06-24

    We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse.

  8. Plasma perturbation induced by laser photodetachment.

    PubMed

    Nishiura, M; Sasao, M; Wada, M; Bacal, M

    2001-03-01

    The plasma dynamics arising from laser photodetachment is discussed herein theoretically and experimentally. The hybrid fluid-kinetic model, where the positive ions and electrons are treated by the fluid theory and the negative ions are treated within the ballistic approximation, is extended and applied to the analysis of densities perturbed by laser photodetachment. The agreement between the theory and measured data confirms the validity of the considered plasma dynamics model. This model, including the positive ion perturbation, shows a good agreement with the time evolution and the spatial distribution of perturbed electron densities which are measured by a Langmuir probe inside and outside the laser beam. From the overshoot in the time evolution of perturbed electron current in the center of the laser beam, the positive ion temperature was found to be in the range 0.1-0.25 eV, while the electron temperature changes from 0.3 to 3.2 eV.

  9. Laser-induced quantum pumping in graphene

    SciTech Connect

    San-Jose, Pablo; Prada, Elsa; Kohler, Sigmund; Schomerus, Henning

    2012-10-08

    We investigate non-adiabatic electron pumping in graphene generated by laser irradiation with linear polarization parallel or perpendicular to the transport direction. Transport is dominated by the spatially asymmetric excitation of electrons from evanescent into propagating modes. For a laser with parallel polarization, the pumping response exhibits a subharmonic resonant enhancement which directly probes the Fermi energy; no such enhancement occurs for perpendicular polarization. The resonance mechanism relies on the chirality of charge carriers in graphene.

  10. Morphometric Optic Nerve Head Analysis in Glaucoma Patients: A Comparison between the Simultaneous Nonmydriatic Stereoscopic Fundus Camera (Kowa Nonmyd WX3D) and the Heidelberg Scanning Laser Ophthalmoscope (HRT III).

    PubMed

    Mariacher, Siegfried; Hipp, Stephanie; Wirthky, Robert; Blumenstock, Gunnar; Bartz-Schmidt, Karl-Ulrich; Ziemssen, Focke; Schiefer, Ulrich; Voykov, Bogomil; Januschowski, Kai

    2016-01-01

    Purpose. To investigate the agreement between morphometric optic nerve head parameters assessed with the confocal laser ophthalmoscope HRT III and the stereoscopic fundus camera Kowa nonmyd WX3D retrospectively. Methods. Morphometric optic nerve head parameters of 40 eyes of 40 patients with primary open angle glaucoma were analyzed regarding their vertical cup-to-disc-ratio (CDR). Vertical CDR, disc area, cup volume, rim volume, and maximum cup depth were assessed with both devices by one examiner. Mean bias and limits of agreement (95% CI) were obtained using scatter plots and Bland-Altman analysis. Results. Overall vertical CDR comparison between HRT III and Kowa nonmyd WX3D measurements showed a mean difference (limits of agreement) of -0.06 (-0.36 to 0.24). For the CDR < 0.5 group (n = 24) mean difference in vertical CDR was -0.14 (-0.34 to 0.06) and for the CDR ≥ 0.5 group (n = 16) 0.06 (-0.21 to 0.34). Conclusion. This study showed a good agreement between Kowa nonmyd WX3D and HRT III with regard to widely used optic nerve head parameters in patients with glaucomatous optic neuropathy. However, data from Kowa nonmyd WX3D exhibited the tendency to measure larger CDR values than HRT III in the group with CDR < 0.5 group and lower CDR values in the group with CDR ≥ 0.5.

  11. Laser acupuncture in children and adolescents with exercise induced asthma

    PubMed Central

    Gruber, W; Eber, E; Malle-Scheid, D; Pfleger, A; Weinhandl, E; Dorfer, L; Zach, M

    2002-01-01

    Background: Laser acupuncture, a painless technique, is a widely used alternative treatment method for childhood asthma, although its efficacy has not been proved in controlled clinical studies. Methods: A double blind, placebo controlled, crossover study was performed to investigate the possible protective effect of a single laser acupuncture treatment on cold dry air hyperventilation induced bronchoconstriction in 44 children and adolescents of mean age 11.9 years (range 7.5–16.7) with exercise induced asthma. Laser acupuncture was performed on real and placebo points in random order on two consecutive days. Lung function was measured before laser acupuncture, immediately after laser acupuncture (just before cold dry air challenge (CACh)), and 3 and 15 minutes after CACh. CACh consisted of a 4 minute isocapnic hyperventilation of –10°C absolute dry air. Results: Comparison of real acupuncture with placebo acupuncture showed no significant differences in the mean maximum CACh induced decrease in forced expiratory volume in 1 second (27.2 (18.2)% v 23.8 (16.2)%) and maximal expiratory flow at 25% remaining vital capacity (51.6 (20.8)% v 44.4 (22.3)%). Conclusions: A single laser acupuncture treatment offers no protection against exercise induced bronchoconstriction in paediatric and adolescent patients. PMID:11867825

  12. Glaucoma in atomic bomb survivors.

    PubMed

    Kiuchi, Yoshiaki; Yokoyama, Tomoko; Takamatsu, Michiya; Tsuiki, Eiko; Uematsu, Masafumi; Kinoshita, Hirofumi; Kumagami, Takeshi; Kitaoka, Takashi; Minamoto, Atsushi; Neriishi, Kazuo; Nakashima, Eiji; Khattree, Ravindra; Hida, Ayumi; Fujiwara, Saeko; Akahoshi, Masazumi

    2013-10-01

    Radiation has been associated with increases in noncancerous diseases. An effect of low-dose radiation on the prevalence of clinically detected glaucoma has not been previously reported. We therefore investigated the prevalence of glaucoma in A-bomb survivors and its possible association with radiation dose. A total of 1,589 people who participated in the clinical examination program for A-bomb survivors at the Radiation Effects Research Foundation (RERF) between October 2006 and September 2008 and who had reconstructed radiation doses, were recruited into this cross-sectional screening study. The prevalence of glaucoma and its dose-response relationship to A-bomb radiation were measured. Each subject underwent an initial screening consisting of an interview and ophthalmological examination. Questionable cases with any indication of ocular disease, including glaucoma, were referred to local hospitals for more comprehensive evaluation. A diagnosis of glaucoma was made based on specific optic disc appearance, perimetric results and other ocular findings. Of 1,589 eligible people, we detected 284 (17.9%) cases of glaucoma overall, including 36 (2.3%) cases of primary open-angle glaucoma with intraocular pressure levels greater than 21 mmHg, 226 (14.2%) cases of normal-tension glaucoma and 25 (1.6%) cases of primary angle-closure glaucoma. Seven glaucoma risk factors were examined as potential confounders but only two needed to be included in the final model. Binary regression using a generalized estimating equation method, with adjustment for gender, age, city, cataract surgery or diabetes mellitus, revealed an odds ratio at 1 Gy of 1.31 (95% confidence interval 1.11-1.53, P = 0.001) in the case of normal-tension glaucoma, but no association for other types of glaucoma. The prevalence of normal-tension glaucoma may increase with A-bomb radiation dose, but uncertainties associated with nonparticipation (59% participation) suggest caution in the interpretation of these

  13. Glaucoma in atomic bomb survivors.

    PubMed

    Kiuchi, Yoshiaki; Yokoyama, Tomoko; Takamatsu, Michiya; Tsuiki, Eiko; Uematsu, Masafumi; Kinoshita, Hirofumi; Kumagami, Takeshi; Kitaoka, Takashi; Minamoto, Atsushi; Neriishi, Kazuo; Nakashima, Eiji; Khattree, Ravindra; Hida, Ayumi; Fujiwara, Saeko; Akahoshi, Masazumi

    2013-10-01

    Radiation has been associated with increases in noncancerous diseases. An effect of low-dose radiation on the prevalence of clinically detected glaucoma has not been previously reported. We therefore investigated the prevalence of glaucoma in A-bomb survivors and its possible association with radiation dose. A total of 1,589 people who participated in the clinical examination program for A-bomb survivors at the Radiation Effects Research Foundation (RERF) between October 2006 and September 2008 and who had reconstructed radiation doses, were recruited into this cross-sectional screening study. The prevalence of glaucoma and its dose-response relationship to A-bomb radiation were measured. Each subject underwent an initial screening consisting of an interview and ophthalmological examination. Questionable cases with any indication of ocular disease, including glaucoma, were referred to local hospitals for more comprehensive evaluation. A diagnosis of glaucoma was made based on specific optic disc appearance, perimetric results and other ocular findings. Of 1,589 eligible people, we detected 284 (17.9%) cases of glaucoma overall, including 36 (2.3%) cases of primary open-angle glaucoma with intraocular pressure levels greater than 21 mmHg, 226 (14.2%) cases of normal-tension glaucoma and 25 (1.6%) cases of primary angle-closure glaucoma. Seven glaucoma risk factors were examined as potential confounders but only two needed to be included in the final model. Binary regression using a generalized estimating equation method, with adjustment for gender, age, city, cataract surgery or diabetes mellitus, revealed an odds ratio at 1 Gy of 1.31 (95% confidence interval 1.11-1.53, P = 0.001) in the case of normal-tension glaucoma, but no association for other types of glaucoma. The prevalence of normal-tension glaucoma may increase with A-bomb radiation dose, but uncertainties associated with nonparticipation (59% participation) suggest caution in the interpretation of these

  14. Neuroprotective effects of VCP modulators in mouse models of glaucoma.

    PubMed

    Nakano, Noriko; Ikeda, Hanako Ohashi; Hasegawa, Tomoko; Muraoka, Yuki; Iwai, Sachiko; Tsuruyama, Tatsuaki; Nakano, Masaki; Fuchigami, Tomohiro; Shudo, Toshiyuki; Kakizuka, Akira; Yoshimura, Nagahisa

    2016-04-01

    Glaucoma is a major cause of adult blindness due to gradual death of retinal ganglion cells. Currently, no therapeutics are available for the protection of these cells from the cell death. We have recently succeeded in synthesizing novel compounds, KUSs (Kyoto University Substances), which can reduce cellular ATP consumption by specifically inhibiting the ATPase activities of VCP, a major ATPase in the cell, and we have shown that KUSs could mitigate the disease progression of rd10, a mouse model of retinitis pigmentosa, without any apparent side effects. Here we show that KUSs (e.g. KUS121 and KUS187) can prevent antimycin- and oligomycin-induced ATP depletion, endoplasmic reticulum (ER) stress, and cell death in neuronally differentiated PC12 cells. Furthermore, KUSs manifest significant efficacies on several mouse models of glaucoma. KUS administration prevented or mitigated ER stress and subsequent apoptotic cell death of retinal ganglion cells in an acute injury mouse model of retinal ganglion cell loss, which was induced with N-methyl-D-aspartate. In a mouse model of glaucoma with high intraocular pressure, KUSs prevented the typical glaucoma pathologies, i.e. enlargement of optic disc cupping and thinning of the retinal nerve fiber layer. KUSs also preserved visual functions in GLAST knockout mice, a mouse model for chronic retinal ganglion cell loss. We propose "ATP maintenance" via inhibition of ATPase activities of VCP as a promising new neuroprotective strategy for currently incurable eye diseases, such as glaucoma. PMID:27441270

  15. Nanoparticles based laser-induced surface structures formation on mesoporous silicon by picosecond laser beam interaction

    NASA Astrophysics Data System (ADS)

    Talbi, A.; Petit, A.; Melhem, A.; Stolz, A.; Boulmer-Leborgne, C.; Gautier, G.; Defforge, T.; Semmar, N.

    2016-06-01

    In this study, laser induced periodic surface structures were formed on mesoporous silicon by irradiation of Nd:YAG picosecond pulsed laser beam at 266 nm wavelength at 1 Hz repetition rate and with 42 ps pulse duration. The effects of laser processing parameters as laser beam fluence and laser pulse number on the formation of ripples were investigated. Scanning electron microscopy and atomic force microscopy were used to image the surface morphologies and the cross section of samples after laser irradiation. At relatively low fluence ∼20 mJ/cm2, ripples with period close to the laser beam wavelength (266 nm) and with an always controlled orientation (perpendicular to the polarization of ps laser beam) appeared after a large laser pulse number of 12,000. It has been found that an initial random distribution of SiOx nanoparticles is periodically structured with an increase of the laser pulse number. Finally, it is experimentally demonstrated that we formed a 100 nm liquid phase under the protusion zones including the pores in the picosecond regime.

  16. Laser wavelength effect on laser-induced photo-thermal sintering of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Paeng, Dongwoo; Yeo, Junyeob; Lee, Daeho; Moon, Seung-Jae; Grigoropoulos, Costas P.

    2015-09-01

    This work is concerned with the laser wavelength effect on the electrical properties and surface morphology of laser-sintered nanoparticle thin films. Silver nanoparticle thin films spin-coated on soda lime glass substrates were irradiated with lasers of three different wavelengths (near ultraviolet 405 nm, green 514.5 nm, near infrared 817 nm) at varied laser intensities and scanning speeds. Scanning electron microscopy images and ex situ resistivity measurements show that the photo-thermal sintering alters significantly the film surface morphology and electrical properties, depending on the processing parameters (laser wavelength, laser intensities and scanning speed). While the optical response of the material is determined largely by the processing laser wavelength, the laser beam intensity and scanning speed regulate the induced temperature field. Examination of the optical properties of as-deposited silver nanoparticle thin film in conjunction with scanning electron microscopy images taken from the laser-sintered lines helps elucidate how the processing laser wavelength modulates the optical response of silver nanoparticle thin film and therefore affects the thermal response.

  17. Neuroprotective therapy for argon-laser-induced retinal injury

    NASA Astrophysics Data System (ADS)

    Belkin, Michael; Rosner, Mordechai; Solberg, Yoram; Turetz, Yosef

    1999-06-01

    Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcim-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were sacrificed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent nomral retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invations of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated wtih argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser expsoure, the rats were sacrificed and their lesions were

  18. Laser-induced acoustic emissions in experimental dental composites.

    PubMed

    Lee, S Y; Lin, C T; Keh, E S; Pan, L C; Huang, H M; Shih, Y H; Cheng, H C

    2000-07-01

    A laser thermoacoustic technique was innovated to evaluate laser-induced acoustic emissions (AEs) in experimental dental composites aged with 75% ethanol solution. Experimental composite systems of 75/25 BisGMA/TEGDMA resin filled with 0, 12.6, 30.0, and 56.5 vol% of 8-microm silanized and unsilanized BaSiO6 were analyzed. The sample size was 4.65 mm (diameter) x 0.5 mm (thick). Aging effects of immersing in 75% ethanol for up to 14 h on AEs were then evaluated. A continuous-wave CO2 laser was used to heat the samples. Acoustic emissions were collected as a function of filler fraction, laser power, silanization, and immersion time. Onset of burst-pattern acoustic signals characteristic of fracturing occurred at different laser powers for different tested groups. Acoustic emissions generally increased with laser power, in which lower laser powers produced low-amplitude (45-50 dB) signals; the amplitude distribution (50-85 dB) became more extensive as laser powers increased. After immersion, the lower laser powers could produce the same phenomenon. The higher the filler fraction, the fewer AEs generated. A large percentage AE reduction due to silanization was noted as a function of filler fraction. Unsilanized specimens showed more thermal damages than did silanized ones.

  19. Neuroprotective therapies for glaucoma

    PubMed Central

    Song, Wei; Huang, Ping; Zhang, Chun

    2015-01-01

    Glaucoma is the second leading cause for blindness worldwide. It is mainly caused by glaucomatous optic neuropathy (GON) characterized by retinal ganglion cell loss, which leads to visual field defect and blindness. Up to now, the main purpose of antiglaucomatous therapies has been to lower intraocular pressure (IOP) through surgeries and medications. However, it has been found that progressive GON is still present in some patients with effective IOP decrease. Therefore, risk factors other than IOP elevation, like neurotrophin deprivation and excitotoxicity, contribute to progressive GON. Novel approaches of neuroprotection may be more effective for preserving the function of the optic nerve. PMID:25792807

  20. Lifestyle, Nutrition and Glaucoma

    PubMed Central

    Pasquale, Louis R.; Kang, Jae Hee

    2009-01-01

    The only proven strategy to prevent primary open-angle glaucoma (POAG) is the use of ocular hypotensive therapy among people diagnosed with ocular hypertension. In this review, various modifiable lifestyle factors, such as exercise, diet and cigarette smoking, that may influence intraocular pressure and that have been studied in relation to the risk of developing POAG are discussed. Epidemiologic studies on lifestyle factors are few, and the current evidence suggests that there are no environmental factors that are clearly associated with POAG; however, a few factors merit further study. This review also outlines future directions for research into the primary prevention of POAG. PMID:19680048

  1. Validation of a glaucoma knowledge assessment in glaucoma patients

    PubMed Central

    Rao, Veena S; Peralta, Esteban A; Rosdahl, Jullia A

    2016-01-01

    Summary To develop metrics to identify knowledge deficits and barriers to learning in glaucoma patients, this study seeks to validate a glaucoma knowledge assessment to use in the evaluation of knowledge in glaucoma patients. Purpose Glaucoma treatment adherence appears to improve when patients demonstrate a greater knowledge of the disease and its treatment. This study seeks to validate a glaucoma knowledge assessment in a glaucoma patient population to assist in patient educational assessments and interventions. Patients and methods The National Eye Health Education Program’s (NEHEP) glaucoma knowledge assessment has previously been suggested as a useful measure to assess glaucoma patient’s knowledge. This questionnaire was administered in glaucoma patients along with a more comprehensive 49-question examination. Demographic data and health literacy were assessed. Statistical analyses were performed to assess the validity of the assessments. Results A total of 12 glaucoma patients completed the knowledge assessments. The mean ± standard deviation age of the patients was 69±14 years, and the duration of glaucoma was 14±13 years. The participants’ mean score on the NEHEP assessment was 7.3±0.8 (of 10, 73% correct) vs 29.3±7.3 (of 49, 60% correct) on the comprehensive assessment. The value of coefficient α was 0.592 for NEHEP and 0.872 for the cumulative assessment. The P-value (proportion of examinees answering correctly) ranged from 0 to 1 for individual questions. Item point–biserial correlation values for each question ranged from −0.402 to 0.813. Discussion The NEHEP quiz may be a good starting point for the development of a reliable knowledge assessment tool to measure and monitor glaucoma knowledge, due to its concise nature and reasonable level of difficulty. This study suggests that questions included in the currently available questionnaires vary widely in difficulty and ability to differentiate knowledge level, which may ultimately

  2. Pulsed UV laser induced desorption of ions from aluminum

    NASA Astrophysics Data System (ADS)

    Taylor, David Paul; Helvajian, Henry

    2000-04-01

    A study of pulsed UV laser induced desorption (LID) has been performed on an Al(111) sample. The positive ion desorption was investigated at low laser fluence, in a regime in which the ion yield exhibits a highly non-linear dependence on the laser fluence. The peak of the kinetic energy distribution of the desorbed ions has been measured to be about 15 eV. This result is consistent with the conjecture that the ion departing the metal surface can acquire a kinetic energy kick from a process associated with plasmon annihilation. The Al + ion kinetic energy peak is asymmetric and about 3 eV full-width at half-maximum (FWHM). This experiment indicates that plasmon excitation can play a significant role in laser stimulated desorption induced by electronic transitions (DIET).

  3. Detection of early caries by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji

    2015-07-01

    To improve sensitivity of dental caries detection by laser-induced breakdown spectroscopy (LIBS) analysis, it is proposed to utilize emission peaks in the ultraviolet. We newly focused on zinc whose emission peaks exist in ultraviolet because zinc exists at high concentration in the outer layer of enamel. It was shown that by using ratios between heights of an emission peak of Zn and that of Ca, the detection sensitivity and stability are largely improved. It was also shown that early caries are differentiated from healthy part by properly setting a threshold in the detected ratios. The proposed caries detection system can be applied to dental laser systems such as ones based on Er:YAG-lasers. When ablating early caries part by laser light, the system notices the dentist that the ablation of caries part is finished. We also show the intensity of emission peaks of zinc decreased with ablation with Er:YAG laser light.

  4. OH Planar Laser-Induced Fluorescence from Microgravity Droplet Combustion

    NASA Technical Reports Server (NTRS)

    Winter, Michael; Wegge, Jason; Kang, Kyung-Tae

    1997-01-01

    Droplet combustion under microgravity conditions has been extensively studied, but laser diagnostics have just begun to be employed in microgravity droplet experiments. This is due in part to the level of difficulty associated with laser system size, power and economic availability. Hydroxyl radical (OH) is an important product of combustion, and laser-induced fluorescence (LIF) has proved to be an adequate and sensitive tool to measure OH. In this study, a frequency doubled Nd:YAG laser and a doubled dye laser, compact and reliable enough to perform OH PLIF experiments aboard a parabolic flight-path aircraft, has been developed and successfully demonstrated in a methanol droplet flame experiment. Application to microgravity conditions is planned aboard parabolic flight-path aircraft.

  5. Laser Induced Breakdown Spectroscopy:. AN Application on Multilayered Archeological Ceramics

    NASA Astrophysics Data System (ADS)

    Ponterio, R.; Trusso, S.; Vasi, C.; Aragona, S.; Mavilia, L.

    2004-10-01

    In this work we show an example of application of Laser Induced Breakdown Spectroscopy (LIBS) in combination with another laser-based technique: Raman micro-spectroscopy for the identification of pigments and glaze on pottery found archaeological excavations in Amendolea castle site (south of Italy in Calabrian peninsula); the objects belong to medieval period. The spectral data indicates the qualitative elemental composition of the examined materials and, in addition, give us useful information on the stratigraphy of the paint layers.

  6. Post-acceleration of laser-induced ion beams

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Delle Side, D.

    2015-04-01

    A complete review of the essential and recent developments in the field of post-acceleration of laser-induced ion beams is presented. After a brief introduction to the physics of low-intensity nanosecond laser-matter interaction, the details of ions extraction and acceleration are critically analyzed and the key parameters to obtain good-quality ion beams are illustrated. A description of the most common ion beam diagnosis system is given, together with the associated analytical techniques.

  7. Correlated or not: Glaucoma prevalence and modern industrialization.

    PubMed

    Wang, Lijun; Zhang, Xiulan; Cai, Shuping; Ma, Jia; Liu, Xuyang; Wang, Ningli

    2011-02-01

    The higher prevalence of primary angle-closure glaucoma (PACG) among Eskimos, Chinese and Mongolians has long been acknowledged, while primary open-angle glaucoma (POAG) is common in blacks and Caucasians. However, in recent years, the incidence of Chinese POAG has increased to a level similar to that of Western countries, and the urban prevalence is higher than the rural one. Is this a coincidental result, or is it a consequence of modern industrialization? The etiology of glaucoma is believed to be due to both genetic and environmental factors. Genetics plays an important role in the growth of the eye, as demonstrated in ethnic variations in glaucoma prevalence and family studies. At the same time, changes in environmental factors have resulted in countries experiencing one of the most rapid epidemiological transitions in history. For the modern human eye to adapt to a more close-up working environment, and with more education requiring close reading, there have been some changes in the eye structure, including a deepening of the anterior chamber, an increase in myopia, a decrease of hyperopia, etc. The changes in these factors were closely associated with the pathogenesis of glaucoma. And of these factors, myopia may have been the most important contributor. Myopia, as an independent risk factor, may increase susceptibility to glaucomatous damage of the optic nerve in myopic eyes. Myopic eyes are more sensitive to intraocular pressure (IOP) (even normal IOP)-induced stress for the thinner lamina cribrosa and larger scleral canal than emmetropic eyes. Axial myopia has longer axial length of the eye and deeper anterior chamber than the normal eye, leading to a less chance to develop angle-closure glaucoma. Due to the increase in myopia among the younger generation in the process of industrialization and urbanization, we hypothesize that the prevalence of glaucoma is correlated with these changes, and that POAG could become more common in Eskimos, Chinese and other

  8. Latent laser-induced graphitization of diamond

    NASA Astrophysics Data System (ADS)

    Kononenko, V. V.; Gololobov, V. M.; Konov, V. I.

    2016-03-01

    Basic features and mechanism of femtosecond laser graphitization of diamond surface were studied in the two regimes of irradiation: (1) by an intensive (>10 J/cm2) single shot and (2) by a train of pulses with near-threshold intensity (~1-10 J/cm2). Special attention was paid to the so-called accumulative regime, when multipulse laser treatment results in prolonged delay of an appearance of crystal modification of the crystal. The light absorption mechanisms dominating in each regime are discussed. The experiments with fundamental (800 nm), second (400 nm) and third (266 nm) harmonics of Ti-sapphire laser (100 fs) have revealed that thermally stimulated processes play an essential role in latent diamond graphitization.

  9. Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Z. K.; Zheng, H. Y.; Lim, C. P.; Lam, Y. C.

    2009-09-01

    Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm2 produced a hydrophobic surface and 2.1 to 52.7 J/cm2 (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm2 had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness.

  10. Thermally induced birefringence in Nd:YAG slab lasers

    SciTech Connect

    Ostermeyer, Martin; Mudge, Damien; Veitch, Peter J.; Munch, Jesper

    2006-07-20

    We study thermally induced birefringence in crystalline Nd:YAG zigzag slab lasers and the associated depolarization losses. The optimum crystallographic orientation of the zigzag slab within the Nd:YAG boule and photoelastic effects in crystalline Nd:YAG slabs are briefly discussed. The depolarization is evaluated using the temperature and stress distributions, calculated using a finite element model, for realistically pumped and cooled slabs of finite dimensions. Jones matrices are then used to calculate the depolarization of the zigzag laser mode. We compare the predictions with measurements of depolarization, and suggest useful criteria for the design of the gain media for such lasers.

  11. Laser-Induced Underwater Plasma And Its Spectroscopic Applications

    SciTech Connect

    Lazic, Violeta

    2008-09-23

    Applications of Laser Induced Breakdown Spectroscopy (LIBS) for analysis of immersed solid and soft materials, and for liquid impurities are described. A method for improving the LIBS signal underwater and for obtaining quantitative analyses in presence of strong shot-to-shot variations of the plasma properties is proposed. Dynamic of the gas bubble formed by the laser pulse is also discussed, together with its importance in Double-Pulse (DP) laser excitation. Results of the studies relative to an application of multi-pulse sequence and its effects on the plasma and gas bubble formation are also presented.

  12. Trace metal mapping by laser-induced breakdown spectroscopy

    SciTech Connect

    Kaiser, Jozef; Novotny, Dr. Karel; Hrdlicka, A; Malina, R; Hartl, M; Kizek, R; Adam, V

    2012-01-01

    Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) is a sensitive optical technique capable of fast multi-elemental analysis of solid, gaseous and liquid samples. The potential applications of lasers for spectrochemical analysis were developed shortly after its invention; however the massive development of LIBS is connected with the availability of powerful pulsed laser sources. Since the late 80s of 20th century LIBS dominated the analytical atomic spectroscopy scene and its application are developed continuously. Here we review the utilization of LIBS for trace elements mapping in different matrices. The main emphasis is on trace metal mapping in biological samples.

  13. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wang, Ten-See (Technical Monitor)

    2002-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid, pressure-based computational aerothermodynamics; platform, several sub-models describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (IB) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  14. Laser-induced air ionization microscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Zhang, N.; Yang, J.; Zhu, X.

    2006-06-01

    A nonlinear scanning imaging method is introduced that uses the highly localized air ionization initiated by photoelectrons from the sample surface under irradiation of femtosecond laser pulses as the microprobe. This type of microscopy with realizable subdiffraction spatial resolution has the unique advantages of being highly sensitive to both elemental and topographical properties of the samples of interest. Microscopic images of a femtosecond laser ablated micropattern, the cross section and the side view profile of an optical fiber, and a fresh mulberry leaf are obtained with this imaging technique, which demonstrate this technique's broad applicability in microscopic studies of different materials.

  15. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wnag, Ten-See (Technical Monitor)

    2001-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid., pressure-based computational aerothermodynamics, platform, several sub-nio"'dels describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (113) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  16. Resonance fluorescence spectroscopy in laser-induced cavitation bubbles.

    PubMed

    Koch, Sandra; Garen, Walter; Neu, Walter; Reuter, Rainer

    2006-05-01

    Laser-induced breakdown spectroscopy (LIBS) in liquids using a double-pulse Q-switched Nd:YAG laser system has provided reliable results that give trace detection limits in water. Resonant laser excitation has been added to enhance detection sensitivity. A primary laser pulse (at 532 nm), transmitted via an optical fiber, induces a cavitation bubble and shockwave at a target immersed in a 10 mg l(-1)-100 mg l(-1) indium (In) water suspension. The low-pressure rear of the shockwave induces bubble expansion and a resulting reduction in cavity pressure as it extends away from the target. Shortly before the maximum diameter is expected, a secondary laser pulse (also at 532 nm) is fed into the bubble in order to reduce quenching processes. The plasma field generated is then resonantly excited by a fiber-guided dye laser beam to increase detection selectivity. The resulting resonance fluorescence emission is optically detected and processed by an intensified optical multichannel analyzer system.

  17. Nasal Retinoschisis Associated with Glaucoma.

    PubMed

    Hubschman, Jean-Pierre; Reddy, Shantan; Kaines, Andrew; Law, Simon

    2010-03-01

    The authors describe a case of nasal and macular retinoschisis in a patient with open angle glaucoma. A 75 year-old female with optic nerve head damage secondary to chronic open angle glaucoma developed macular schisis and a separate area of retinoschisis nasal to her optic disk. There were no other identifiable causes for her retinoschisis. Glaucoma related structural defects offer a plausible explanation for multiple cavities of retinoschisis in favor of multiple occult congenital pits of the optic nerve head. PMID:20337311

  18. Laser-induced fluorescence of space-exposed polyurethane

    NASA Technical Reports Server (NTRS)

    Hill, Ralph H., Jr.

    1993-01-01

    The object of this work was to utilize laser-induced fluorescence technique to characterize several samples of space-exposed polyurethane. These samples were flown on the Long Duration Exposure Facility (LDEF), which was in a shuttle-like orbit for nearly 6 years. Because of our present work to develop laser-induced-fluorescence inspection techniques for polymers, space-exposed samples and controls were lent to us for evaluation. These samples had been attached to the outer surface of LDEF; therefore, they were subjected to thermal cycling, solar ultraviolet radiation, vacuum, and atomic oxygen. It is well documented that atomic oxygen and ultraviolet exposure have detrimental effects on many polymers. This was a unique opportunity to make measurements on material that had been naturally degraded by an unusual environment. During our past work, data have come from artificially degraded samples and generally have demonstrated a correlation between laser-induced fluorescence and tensile strength or elasticity.

  19. Laser-induced fluorescence detection of dysplasia in Barrett's esophagus

    NASA Astrophysics Data System (ADS)

    Panjehpour, Masoud; Overholt, Bergein F.; Vo-Dinh, Tuan; Edwards, Donna H.; Buckley, Paul F., III; DeCosta, Joseph F.; Haggitt, Rodger C.

    1996-04-01

    A study was conducted to determine whether laser-induced fluorescence could detect high grade dysplasia in Barrett's esophagus. Four-hundred-ten nm laser light was used to induce autofluorescence of Barrett's mucosa in 36 patients during routine endoscopy. The spectra were analyzed using the Differential Normalized Fluorescence (DNF) Index technique to differentiate high grade dysplasia from either low grade or non-dysplastic mucosa. Each spectrum was classified as either premalignant or benign using two different DNF indices. Analyzing the fluorescence spectra from all patients using one DNF Index, 96% of non- dysplastic Barrett's samples classified as benign tissue. All low grade dysplasia samples classified as benign. Ninety percent of high grade dysplasia samples classified as premalignant. Twenty-eight percent of mixed low grade/focal high grade dysplasia samples classified as premalignant. In summary, high grade dysplasia in Barrett's esophagus patients can be detected by endoscopic laser-induced fluorescence spectroscopy using differential normalized fluorescence technique.

  20. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, Tuan; Panjehpour, Masoud; Overholt, Bergein F.

    1996-01-01

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample.

  1. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, T.; Panjehpour, M.; Overholt, B.F.

    1996-12-03

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample. 5 figs.

  2. Infrared Laser-Induced Breakdown Spectroscopy of Alkali Metal Halides

    NASA Astrophysics Data System (ADS)

    Brown, Ei; Hommerich, Uwe; Yang, Clayton; Trivedi, Sudhir; Samuels, Alan; Snyder, Peter

    2008-10-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. LIBS is a relatively simple technique and has been successfully employed in applications such as environmental monitoring, materials analysis, medical diagnostics, industrial process control, and homeland security. Most LIBS applications are limited to emission features in the ultraviolet-visible-near infrared (UV-VIS-NIR) region arising from atoms and simple molecular fragments. In the present work, we report on the observation of mid- infrared emission lines from alkali metal halides due to laser-induced breakdown processes. The studied alkali metal halides included LiCl, NaCl, NaBr, KCl, KBr, KF, RbCl, and RbBr. The laser-induced plasma was produced by focusing a 16 mJ pulsed Nd:YAG laser (1064 nm) on the target. The LIBS infrared emission from alkali halides showed intense and narrow bands located in the region from 2-8 μm. The observed emission features were assigned to atomic transitions between higher-lying Rydberg states of neutral alkali atoms. More detailed results of the performed IR LIBS studies on alkali metal halides will be discussed at the conference.

  3. Ultraviolet Laser-induced ignition of RDX single crystal.

    PubMed

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm(2). The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  4. Chemical consequences of laser-induced breakdown in molecular gases

    NASA Astrophysics Data System (ADS)

    Babánková, Dagmar; Civiš, Svatopluk; Juha, Libor

    This article gives an account of chemical reactions initiated by laser-induced dielectric breakdown (LIDB) in homogeneous molecular gases. The systematic part of the article describes the laser-plasma-chemical behavior of simple inorganic gases and their mixtures, metal carbonyls and organometallics, and organic molecular gases. Research on LIDB-initiated chemical reactions producing well-defined fine solid particles has been triggered again recently by the advent of nanotechnologies. Laser ignition of fuel mixtures is also a well researched branch of laser-plasma chemistry because of strong commercial and military interests. However, the strongest current impulses for studying laser-spark chemistry come from planetary sciences, where laser sparks have been used as a laboratory model of high-energy-density phenomena (e.g., impact of extraterrestrial bodies, lightning) in planetary atmospheres. A single pulse from a high-power laser system was used to develop an improved method for investigating this phenomenon. The particular processes responsible for the chemical action of a laser spark are identified and described in detail by the end of the article.

  5. Ultraviolet Laser-induced ignition of RDX single crystal

    PubMed Central

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  6. Laser induced mortality of Anopheles stephensi mosquitoes

    NASA Astrophysics Data System (ADS)

    Keller, Matthew D.; Leahy, David J.; Norton, Bryan J.; Johanson, Threeric; Mullen, Emma R.; Marvit, Maclen; Makagon, Arty

    2016-02-01

    Small, flying insects continue to pose great risks to both human health and agricultural production throughout the world, so there remains a compelling need to develop new vector and pest control approaches. Here, we examined the use of short (<25 ms) laser pulses to kill or disable anesthetized female Anopheles stephensi mosquitoes, which were chosen as a representative species. The mortality of mosquitoes exposed to laser pulses of various wavelength, power, pulse duration, and spot size combinations was assessed 24 hours after exposure. For otherwise comparable conditions, green and far-infrared wavelengths were found to be more effective than near- and mid-infrared wavelengths. Pulses with larger laser spot sizes required lower lethal energy densities, or fluence, but more pulse energy than for smaller spot sizes with greater fluence. Pulse duration had to be reduced by several orders of magnitude to significantly lower the lethal pulse energy or fluence required. These results identified the most promising candidates for the lethal laser component in a system being designed to identify, track, and shoot down flying insects in the wild.

  7. Magnetically induced pulser laser excitation system

    SciTech Connect

    Taylor, R.S.; Leopold, K.

    1987-07-07

    An apparatus is described for exciting a laser having first and second electrodes and containing a gas mixture comprising: preionization means for preionizing the gas mixture, primary energy storage means for storing a sufficient electrical energy for the operation of the laser. Energy transfer means connects the primary energy storage means and the first electrode in an impedance matching manner for transferring the sufficient electrical energy the form of a main discharge voltage pulse, trigger pulse generating means forms a part of the primary energy storage means and for generating a trigger pulse in response to the main discharge voltage pulse. Secondary energy storage means stores an electrical energy, electromagnetic energy transfers means connected between the secondary energy storage means and the second electrode for transferring electromagnetically the electrical energy in the form of a high voltage pulse which breaks down the gas mixture. Switching means connects to the electromagnetic energy transfer means for initiating the electromagnetic energy transfer in response to the trigger pulse. The main discharge voltage pulse is longer in duration than the high voltage pulse. The two pulses are coincidental for a period of time to produce gas breakdown in the laser and to permit the energy transfer means for sufficient energy from the primary energy storage means to the laser.

  8. Laser induced mortality of Anopheles stephensi mosquitoes

    PubMed Central

    Keller, Matthew D.; Leahy, David J.; Norton, Bryan J.; Johanson, Threeric; Mullen, Emma R.; Marvit, Maclen; Makagon, Arty

    2016-01-01

    Small, flying insects continue to pose great risks to both human health and agricultural production throughout the world, so there remains a compelling need to develop new vector and pest control approaches. Here, we examined the use of short (<25 ms) laser pulses to kill or disable anesthetized female Anopheles stephensi mosquitoes, which were chosen as a representative species. The mortality of mosquitoes exposed to laser pulses of various wavelength, power, pulse duration, and spot size combinations was assessed 24 hours after exposure. For otherwise comparable conditions, green and far-infrared wavelengths were found to be more effective than near- and mid-infrared wavelengths. Pulses with larger laser spot sizes required lower lethal energy densities, or fluence, but more pulse energy than for smaller spot sizes with greater fluence. Pulse duration had to be reduced by several orders of magnitude to significantly lower the lethal pulse energy or fluence required. These results identified the most promising candidates for the lethal laser component in a system being designed to identify, track, and shoot down flying insects in the wild. PMID:26887786

  9. Laser induced mortality of Anopheles stephensi mosquitoes.

    PubMed

    Keller, Matthew D; Leahy, David J; Norton, Bryan J; Johanson, Threeric; Mullen, Emma R; Marvit, Maclen; Makagon, Arty

    2016-01-01

    Small, flying insects continue to pose great risks to both human health and agricultural production throughout the world, so there remains a compelling need to develop new vector and pest control approaches. Here, we examined the use of short (<25 ms) laser pulses to kill or disable anesthetized female Anopheles stephensi mosquitoes, which were chosen as a representative species. The mortality of mosquitoes exposed to laser pulses of various wavelength, power, pulse duration, and spot size combinations was assessed 24 hours after exposure. For otherwise comparable conditions, green and far-infrared wavelengths were found to be more effective than near- and mid-infrared wavelengths. Pulses with larger laser spot sizes required lower lethal energy densities, or fluence, but more pulse energy than for smaller spot sizes with greater fluence. Pulse duration had to be reduced by several orders of magnitude to significantly lower the lethal pulse energy or fluence required. These results identified the most promising candidates for the lethal laser component in a system being designed to identify, track, and shoot down flying insects in the wild. PMID:26887786

  10. Method for laser induced isotope enrichment

    SciTech Connect

    Pronko, Peter P.; Vanrompay, Paul A.; Zhang, Zhiyu

    2004-09-07

    Methods for separating isotopes or chemical species of an element and causing enrichment of a desired isotope or chemical species of an element utilizing laser ablation plasmas to modify or fabricate a material containing such isotopes or chemical species are provided. This invention may be used for a wide variety of materials which contain elements having different isotopes or chemical species.

  11. Complication of an Ahmed glaucoma valve implant: tube exposure with methicillin-resistant Staphylococcus aureus infection

    PubMed Central

    Pansegrau, Morgan L.; Mengarelli, Eddie; Dersu, Inci Irak

    2015-01-01

    Summary Neovascular glaucoma is commonly treated surgically with implantation of glaucoma drainage devices. We report the case of a 57-year-old man who underwent an uneventful Ahmed glaucoma valve (AGV) placement for radiation-induced neovascular glaucoma but later developed early postoperative infection with tube exposure. The infection was identified 3 weeks postoperatively and antibiotic treatment was immediately initiated. However, the conjunctival melt progressed, and the AGV had to be removed. Culture of the device revealed methicillin-resistant Staphylococcus aureus (MRSA). There is a potential increased risk of postoperative infection and tube exposure following glaucoma valve implantation in patients with previous radiation therapy. To our knowledge, this is the second case in the literature of MRSA causing early postoperative infection following drainage device placement that required explantation. PMID:27330471

  12. Complication of an Ahmed glaucoma valve implant: tube exposure with methicillin-resistant Staphylococcus aureus infection.

    PubMed

    Pansegrau, Morgan L; Mengarelli, Eddie; Dersu, Inci Irak

    2015-01-01

    Neovascular glaucoma is commonly treated surgically with implantation of glaucoma drainage devices. We report the case of a 57-year-old man who underwent an uneventful Ahmed glaucoma valve (AGV) placement for radiation-induced neovascular glaucoma but later developed early postoperative infection with tube exposure. The infection was identified 3 weeks postoperatively and antibiotic treatment was immediately initiated. However, the conjunctival melt progressed, and the AGV had to be removed. Culture of the device revealed methicillin-resistant Staphylococcus aureus (MRSA). There is a potential increased risk of postoperative infection and tube exposure following glaucoma valve implantation in patients with previous radiation therapy. To our knowledge, this is the second case in the literature of MRSA causing early postoperative infection following drainage device placement that required explantation.

  13. Laser-induced fluorescence of formaldehyde in combustion using third harmonic Nd:YAG laser excitation.

    PubMed

    Brackmann, Christian; Nygren, Jenny; Bai, Xiao; Li, Zhongshan; Bladh, Henrik; Axelsson, Boman; Denbratt, Ingemar; Koopmans, Lucien; Bengtsson, Per-Erik; Aldén, Marcus

    2003-12-01

    Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laser-induced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine.

  14. Laser induced damage in multilayer dielectric gratings due to ultrashort laser pulses

    SciTech Connect

    Shore, B.W.; Stuart, B.C.; Feit, M.D.; Rubenchik, A.M.; Perry, M.D.

    1995-05-26

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high-efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize the range of design options for high efficiency gratings. Metal gratings owe their high efficiency to their high conductivity. To avoid the inevitable light absorption that accompanies conductivity, we have developed designs for high efficiency reflection gratings that use only transparent dielectric materials. These combine the reflectivity of a multilayer dielectric stack with a diffraction grating. We report here our present understanding of short-pulse laser induced damage, as it applies to dielectric gratings.

  15. Evaluation of laser-induced thin-layer removal by using shadowgraphy and laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Rabasović, M. S.; Šević, D.; Lukač, N.; Jezeršek, M.; Možina, J.; Gregorčič, P.

    2016-03-01

    Shadow photography and laser-induced breakdown spectroscopy (LIBS) are studied as methods for monitoring the selective removal of thin (i.e., under 100 μm) layers by laser ablation. We used a laser pulse of 5 ns and 16 mJ at 1064 nm to ablate an 18-μm-thin copper layer from the fiberglass substrate. On the basis of shadowgraphs of the laser-induced shock waves, we measured the optodynamic energy-conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation-pulse energy. Our results show that this efficiency is significantly higher for the laser pulse-copper interaction than for the interaction between the excitation pulse and the substrate. LIBS was simultaneously employed in our experimental setup. The optical emission from the plasma plume was collected by using a spectrograph and recorded with a streak camera. We show that advancing of laser ablation through the copper layer and reaching of the substrate can be estimated by tracking the spectral region between 370 and 500 nm. Therefore, the presented results confirm that LIBS method enables an on-line monitoring needed for selective removal of thin layers by laser.

  16. Implants for draining neovascular glaucoma.

    PubMed Central

    Molteno, A C; Van Rooyen, M M; Bartholomew, R S

    1977-01-01

    The implant design, surgical technique, and pharmacological methods of controlling bleb fibrosis, used to treat neovascular glaucoma, are described, together with the results of 14 operations performed on 12 eyes. Images PMID:843508

  17. Does Your Child Have Glaucoma?

    MedlinePlus

    ... Involved News About Us Donate In This Section Does Your Child Have Glaucoma? email Send this article ... for in children under the age of two: Does your child have unusually large eyes? Is there ...

  18. Immune regulation toward immunomodulation for neuroprotection in glaucoma.

    PubMed

    Tezel, Gülgün

    2013-02-01

    Although the immune system functions to preserve and restore tissue homeostasis, accumulating risk factors, prolonged glial activation, and sustained release of pro-inflammatory mediators in glaucoma may lead to a failure in the regulation of stress-induced immune response, and innate immune cells, autoreactive T cells, autoantibodies, and excess complement attack may exhibit potent stimuli that harm retinal ganglion cell somas, axons, and synapses. Identification of the cellular and molecular components of immune response pathways can provide immunomodulatory treatment strategies to attenuate neuroinflammation, protect neural tissue from collateral injury, and enhance endogenous recovery processes. This review highlights the current knowledge of molecular mechanisms regulating neuroinflammation in glaucoma. PMID:23084793

  19. Feasibility of characterizing laser-ablated carbon plasmas via planar laser induced fluorescence

    SciTech Connect

    Bondarenko, A. S.; Schaeffer, D. B.; Everson, E. T.; Constantin, C. G.; Clark, S. E.; Niemann, C.

    2012-10-15

    Planar laser induced fluorescence (PLIF) imaging can potentially assess ion distributions and coupling in the context of super-Alfvenic ablation plasma expansions into magnetized background plasmas. In this feasibility study, we consider the application of PLIF to rapidly expanding carbon plasmas generated via energetic laser ablation of graphite. By utilizing hydrodynamic and collisional-radiative simulations, we identify schemes accessible to commercially available tunable lasers for the C I atom, the C II ion, and the C V ion. We then estimate the signal-to-noise ratios yielded by the schemes under reasonable experimental configurations.

  20. Feline Glaucoma – A Comprehensive Review

    PubMed Central

    McLellan, Gillian J; Miller, Paul E

    2012-01-01

    Cats with glaucoma typically present late in the course of disease. It is likely that glaucoma in cats is under-diagnosed due to its insidious onset and gradual progression, as well as limitations of some commonly used tonometers in this species. Treatment of glaucoma in feline patients presents a clinical challenge, particularly as glaucoma is often secondary to other disease processes in cats. In this review, we consider the clinical features, patho-physiology and classification of the feline glaucomas and provide current evidence to direct selection of appropriate treatment strategies for feline glaucoma patients. PMID:21923820

  1. Comedones Induced by Vascular Laser Therapy

    PubMed Central

    Demirci, Gulsen Tukenmez; Mansur, Ayse Tulin; Gulec, Ayse Tulin

    2016-01-01

    A 21-year-old female presented with acne-like blackheads on brownish areas located on the cheek. She had been treated with neodymium-doped yttrium aluminium garnet (Nd-YAG) laser (1071 nm), 160 j/cm2, three months ago for erythema and telangiectasia of her face. Afterwards, she developed atrophic, slightly depressed, hyperpigmented, 3-4 mm scars with superimposed tiny comedones within the treated areas. Topical treatment with tretinoin 0.05% cream on alternate days, and Sun Protection Factor (SPF) 50 sunscreen daily were commenced. After 2 months, comedones and hyperpigmentation mostly resolved but mild superficial atrophy persisted. According to our knowledge, this is the first case of atrophic scars studded with open comedones, developing shortly after laser therapy used for facial telangiectasia. PMID:27081249

  2. Ruby laser induced emission from NO2

    NASA Technical Reports Server (NTRS)

    Hakala, D. F.; Reeves, R. R.

    1976-01-01

    Two different types of emission from excited NO2 were observed using pulsed ruby laser light at 6943 A. The first type of fluorescence was seen in the near IR and results from the single photon excitation of NO2 from the ground 2-A1 state. By observing the emission as a function of time an unexpected behavior was observed in the near IR and could be explained by a consecutive deactivation mechanism, wherein a secondary species is preferentially detected. A second type of emission recently observed in the blue spectral region is weaker and is due to a multiphoton process. The intensity of the blue emission is a function of the cube of the laser intensity at low pressures and approaches the square at high pressures. This variation is attributed to simultaneous deactivation of the excited NO2 intermediate by collision (square) and by anti-Stokes Raman scattering off of the excited NO2 (cube).

  3. Comedones Induced by Vascular Laser Therapy.

    PubMed

    Demirci, Gulsen Tukenmez; Mansur, Ayse Tulin; Gulec, Ayse Tulin

    2016-01-01

    A 21-year-old female presented with acne-like blackheads on brownish areas located on the cheek. She had been treated with neodymium-doped yttrium aluminium garnet (Nd-YAG) laser (1071 nm), 160 j/cm(2), three months ago for erythema and telangiectasia of her face. Afterwards, she developed atrophic, slightly depressed, hyperpigmented, 3-4 mm scars with superimposed tiny comedones within the treated areas. Topical treatment with tretinoin 0.05% cream on alternate days, and Sun Protection Factor (SPF) 50 sunscreen daily were commenced. After 2 months, comedones and hyperpigmentation mostly resolved but mild superficial atrophy persisted. According to our knowledge, this is the first case of atrophic scars studded with open comedones, developing shortly after laser therapy used for facial telangiectasia. PMID:27081249

  4. Glaucoma drainage implant surgery and ocular surface transplant graft preservation.

    PubMed

    Aref, Ahmad A; Sivaraman, Kavitha R; Djalilian, Ali R

    2015-05-01

    Glaucoma may develop or worsen after ocular surface transplantation and often requires surgical management for adequate intraocular pressure control. Traditional glaucoma filtering procedures in patients with prior ocular surface transplant may be problematic for several reasons, which include mechanical disruption of the pre-existing graft, epithelial and stem cell toxicity induced by antifibrotic agents, and increased risk of future corneal transplantation failure. We describe the implantation of a glaucoma drainage implant via a limbal-based conjunctival incision with tube placement in the ciliary sulcus in three eyes of two patients with prior ocular surface transplantation. At a follow-up interval of 3-7 months, all three eyes have excellent postoperative control of intraocular pressure, stable vision, and healthy ocular surface grafts.

  5. Advanced Morphological and Functional Magnetic Resonance Techniques in Glaucoma

    PubMed Central

    Mastropasqua, Rodolfo; Agnifili, Luca; Mattei, Peter A.; Caulo, Massimo; Fasanella, Vincenzo; Navarra, Riccardo; Mastropasqua, Leonardo; Marchini, Giorgio

    2015-01-01

    Glaucoma is a multifactorial disease that is the leading cause of irreversible blindness. Recent data documented that glaucoma is not limited to the retinal ganglion cells but that it also extends to the posterior visual pathway. The diagnosis is based on the presence of signs of glaucomatous optic neuropathy and consistent functional visual field alterations. Unfortunately these functional alterations often become evident when a significant amount of the nerve fibers that compose the optic nerve has been irreversibly lost. Advanced morphological and functional magnetic resonance (MR) techniques (morphometry, diffusion tensor imaging, arterial spin labeling, and functional connectivity) may provide a means for observing modifications induced by this fiber loss, within the optic nerve and the visual cortex, in an earlier stage. The aim of this systematic review was to determine if the use of these advanced MR techniques could offer the possibility of diagnosing glaucoma at an earlier stage than that currently possible. PMID:26167474

  6. Suprachoroidal Devices in Glaucoma Surgery

    PubMed Central

    Kammer, Jeffrey A.; Mundy, Kevin M.

    2015-01-01

    While conventional glaucoma filtration surgery provides excellent intraocular pressure (IOP) lowering effect, this comes at the expense of significant risks. As the physiology of the suprachoroidal space has become better understood, its potential as a source for aqueous drainage has generated significant interest. This has resulted in the creation of several suprachoroidal glaucoma devices with excellent IOP lowering ability and a much more favorable side effect profile. PMID:25624673

  7. Laser-induced thermal desorption of aniline from silica surfaces

    NASA Astrophysics Data System (ADS)

    Voumard, Pierre; Zenobi, Renato

    1995-10-01

    A complete study on the energy partitioning upon laser-induced thermal desorption of aniline from silica surfaces was undertaken. The measurements include characterization of the aniline-quartz adsorption system using temperature-programmed desorption, the extrapolation of quasiequilibrium desorption temperatures to the regime of laser heating rates on the order of 109-1010 K/s by computational means, measurement of the kinetic energy distributions of desorbing aniline using a pump-probe method, and the determination of internal energies with resonance-enhanced multiphoton ionization spectroscopy. The measurements are compared to calculations of the surface temperature rise and the resulting desorption rates, based on a finite-difference mathematical description of pulsed laser heating. While the surface temperature of laser-heated silica reaches about 600-700 K at the time of desorption, the translational temperature of laser-desorbed aniline was measured to be Tkin=420±60 K, Tvib was 360±60 K, and Trot was 350±100 K. These results are discussed using different models for laser-induced thermal desorption from surfaces.

  8. Laser-induced thermoelastic effects can evoke tactile sensations

    PubMed Central

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  9. Laser-induced thermoelastic effects can evoke tactile sensations.

    PubMed

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  10. Laser-induced thermoelastic effects can evoke tactile sensations

    NASA Astrophysics Data System (ADS)

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-06-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli.

  11. Laser-induced selective copper plating of polypropylene surface

    NASA Astrophysics Data System (ADS)

    Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

    2016-03-01

    Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

  12. Regional Choroidal Blood Flow and Multifocal Electroretinography in Experimental Glaucoma in Rhesus Macaques

    PubMed Central

    Nork, T. Michael; Kim, Charlene B. Y.; Munsey, Kaitlyn M.; Dashek, Ryan J.; Hoeve, James N. Ver

    2014-01-01

    Purpose. To test a hypothesis of regional variation in the effect of experimental glaucoma on choroidal blood flow (ChBF) and retinal function. Methods. Five rhesus macaques underwent laser trabecular destruction (LTD) to induce elevated intraocular pressure (IOP). Intraocular pressures were elevated for 56 to 57 weeks. Multifocal electroretinographic (mfERG) and multifocal visual evoked cortical potential (mfVEP) testing were performed at regular intervals before and during the period of IOP elevation. At euthanasia, the IOP was manometrically controlled at 35 (experimentally glaucomatous eye) and 15 (fellow control eye) mm Hg. Fluorescent microspheres were injected into the left ventricle. Regional ChBF was determined. Results. All of the experimentally glaucomatous eyes exhibited supranormal first-order kernel (K1) root mean square (RMS) early portions of the mfERG waveforms and decreased amplitudes of the late waveforms. The supranormality was somewhat greater in the central macula. Second-order kernel, first slice (K2.1) RMS mfVEP response was inversely correlated (R2 = 0.97) with axonal loss. Total ChBF was reduced in the experimentally glaucomatous eyes. The mean blood flow was 893 ± 123 and 481 ± 37 μL/min in the control and glaucomatous eyes, respectively. The ChBF showed regional variability with the greatest proportional decrement most often found in the central macula. Conclusions. This is the first demonstration of globally reduced ChBF in chronic experimental glaucoma in the nonhuman primate. Both the alteration of mfERG waveform components associated with outer retinal function and the reduction in ChBF were greatest in the macula, suggesting that there may be a spatial colocalization between ChBF and some outer retinal effects in glaucoma. PMID:25370515

  13. Hydrogen leak detection using laser-induced breakdown spectroscopy.

    PubMed

    Ball, A J; Hohreiter, V; Hahn, D W

    2005-03-01

    Laser-induced breakdown spectroscopy (LIBS) is investigated as a technique for real-time monitoring of hydrogen gas. Two methodologies were examined: The use of a 100 mJ laser pulse to create a laser-induced breakdown directly in a sample gas stream, and the use of a 55 mJ laser pulse to create a laser-induced plasma on a solid substrate surface, with the expanding plasma sampling the gas stream. Various metals were analyzed as candidate substrate surfaces, including aluminum, copper, molybdenum, stainless steel, titanium, and tungsten. Stainless steel was selected, and a detailed analysis of hydrogen detection in binary mixtures of nitrogen and hydrogen at atmospheric pressure was performed. Both the gaseous plasma and the plasma initiated on the stainless steel surface generated comparable hydrogen emission signals, using the 656.28 Halpha emission line, and exhibited excellent signal linearity. The limit of detection is about 20 ppm (mass) as determined for both methodologies, with the solid-initiated plasma yielding a slightly better value. Overall, LIBS is concluded to be a viable candidate for hydrogen sensing, offering a combination of high sensitivity with a technique that is well suited to implementation in field environments.

  14. Investigation on laser induced salivary stone fragmentation

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Pongratz, Thomas; Eder, Matthias; Domes, Mona; Vogeser, Michael; Johnson, Thorsten; Siedeck, Vanessa; Schroetzlmair, Florian; Zengel, Pamela

    2014-03-01

    Objective: It was the objective of this in-vitro study to investigate photon-based techniques for identifying the composition and fragmentation of salivary stones using a Ho:YAG laser. Materials and Method: Salivary stones (n=47) extracted from patients with clinical symptoms of sialolithiasis were examined in-vitro. After extraction, the stones were kept in Ringers solution until size and volume measurements could be performed. Thereafter, dual-energy CT scans (DECT) were performed to classify the composition of the stones. Subsequently, fluorescence measurements were performed by taking images under blue light excitation as well as by fluorescence spectroscopy, measuring excitation-emission-matrixes (EEM). Further investigation to identify the exact composition of the stone was performed by Raman spectroscopy and FTIR spectroscopy of stone fragments and debris. Fragmentation was performed in an aquarium set-up equipped with a mesh (hole: 1.5mm) using a Ho:YAG-laser to deliver laser pulses of 0.5, 1.0 and 1.5J/pulse at a frequency of 3Hz through a 200μm-fibre to the stone surface. The collected data were analyzed and fragmentation rates were calculated. Finally, correlation between stone composition and fragmentation was performed. Results: Blue light fluorescence excitation resulted in either fluorescence in the green spectral region or in a combination of green and red fluorescence emission. EEM-measurement showed the corresponding spectra. Raman spectroscopy showed a mixture of carbonate apatite and keratin. DECT results in evidence of calcium containing components. FTIR-spectroscopy results showed that carbonate apatite is the main component. Fragmentation experiment showed a dependency on the energy per pulse applied if the evaluation implies the ratio of fragmented weight to pulse, while the ratio fragmented weight to energy remains about constant for the three laser parameter used. Conclusion: The composition of salivary stones could be determined using

  15. Influence of laser parameters on nanoparticle-induced membrane permeabilization

    NASA Astrophysics Data System (ADS)

    Yao, Cuiping; Qu, Xiaochao; Zhang, Zhenxi; Hüttmann, Gereon; Rahmanzadeh, Ramtin

    2009-09-01

    Light-absorbing nanoparticles that are heated by short laser pulses can transiently increase membrane permeability. We evaluate the membrane permeability by flow cytometry assaying of propidium iodide and fluorescein isothiocyanate dextran (FITC-D) using different laser sources. The dependence of the transfection efficiency on laser parameters such as pulse duration, irradiant exposure, and irradiation mode is investigated. For nano- and also picosecond irradiation, we show a parameter range where a reliable membrane permeabilization is achieved for 10-kDa FITC-D. Fluorescent labeled antibodies are able to penetrate living cells that are permeabilized using these parameters. More than 50% of the cells are stained positive for a 150-kDa IgG antibody. These results suggest that the laser-induced permeabilization approach constitutes a promising tool for targeted delivery of larger exogenous molecules into living cells.

  16. Hydroxylapatite nanoparticles obtained by fiber laser-induced fracture

    NASA Astrophysics Data System (ADS)

    Boutinguiza, M.; Lusquiños, F.; Riveiro, A.; Comesaña, R.; Pou, J.

    2009-03-01

    This work presents the results of laser-induced fragmentation of hydroxylapatite microparticles in water dissolution. Calcined fish bones in form of powder, which were previously milled to achieve microsized particles, were used as precursor material. Two different laser sources were employed to reduce the size of the suspended particles: a pulsed Nd:YAG laser and a Ytterbium doped fiber laser working in continuous wave mode. The morphology as well as the composition of the obtained particles was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and conventional and high resolution transmission electron microscopy (TEM, HRTEM). The results show that nanometric particles of hydroxylapatite and β-tricalcium phosphate as small as 10 nm diameter can be obtained.

  17. Apparatus, system, and method for laser-induced breakdown spectroscopy

    SciTech Connect

    Effenberger, Jr., Andrew J; Scott, Jill R; McJunkin, Timothy R

    2014-11-18

    In laser-induced breakdown spectroscopy (LIBS), an apparatus includes a pulsed laser configured to generate a pulsed laser signal toward a sample, a constructive interference object and an optical element, each located in a path of light from the sample. The constructive interference object is configured to generate constructive interference patterns of the light. The optical element is configured to disperse the light. A LIBS system includes a first and a second optical element, and a data acquisition module. The data acquisition module is configured to determine an isotope measurement based, at least in part, on light received by an image sensor from the first and second optical elements. A method for performing LIBS includes generating a pulsed laser on a sample to generate light from a plasma, generating constructive interference patterns of the light, and dispersing the light into a plurality of wavelengths.

  18. CO2 laser induced refractive index changes in optical polymers.

    PubMed

    Liu, Qing; Chiang, Kin Seng; Reekie, Laurence; Chow, Yuk Tak

    2012-01-01

    We study the infrared photosensitivity properties of two optical polymer materials, benzocyclobutene (BCB) and epoxy OPTOCAST 3505, with a 10.6 μm CO2 laser. We discover that the CO2 laser radiation can lower the refractive index of BCB by as much as 5.5 × 10(-3), while inducing no measurable index change in the epoxy. As confirmed by Fourier transform infrared spectroscopy, the observed index change in BCB can be attributed to photothermal modification of chemical bonds in the material by the CO2 laser radiation. Our findings open up a new possibility of processing polymer materials with a CO2 laser, which could be further developed for application in the areas of post-processing and direct-writing of polymer waveguide devices.

  19. Laser-induced-plasma-assisted ablation for glass microfabrication

    NASA Astrophysics Data System (ADS)

    Hong, Minghui; Sugioka, Koji; Wu, Ding J.; Wong, L. L.; Lu, Yongfeng; Midorikawa, Katsumi; Chong, Tow Chong

    2001-10-01

    Glass is a hard transparent material with many applications in Photonics and advanced display industries. It is a high challenge to achieve crack-free glass microfabrication due to its special material characteristics. Laser-induced-plasma- assisted ablation is applied in this study to get the high quality glass microfabrication. In this processing, the laser beam goes through the glass substrate first and then irradiates on a solid target behind. For laser fluence above ablation threshold for the target, the generated plasma flies forward at a high speed. At a small target-to-substrate distance, there are strong interactions among laser light, target plasma and glass materials at the rear side of the substrate. Light absorption characteristic at the glass substrate is modified since the plasma may soften and dope into the glass in the interaction area. To have a better understanding of this processing, signal diagnostics are carried out to study the dynamic interaction. It is found that glass microfabrication is closely related to laser fluence, target-to-substrate distance, laser spot size and laser beam scanning speed. With proper control of the processing parameters, glass surface marking patterning and cutting can be achieved. With different materials as the targets, color marking of glass substrate can be obtained.

  20. Laser-induced backside wet cleaning technique for glass substrates

    NASA Astrophysics Data System (ADS)

    Weng, Tsu-Shien; Tsai, Chwan-Huei

    2014-08-01

    The aim of this paper is to study the laser-induced backside wet cleaning techniques for glass substrates. Two kinds of laser cleaning techniques are proposed in this study. The first involves applying an Nd:YAG laser to the backside of the substrate which is submerged in water. A metal plate is placed below the glass substrate. Most of the laser energy will be absorbed by the metal plate. The metal then vaporizes the water and generates a turbulent bubble flow. The bubble flow removes the alumina particles from the surface of the glass substrate. The second involves using a CO2 laser to generate turbulent bubble flow to remove the particles. Both methods were successfully demonstrated for the removal of submicron particles of 0.5 μm in size. The phenomena of bubble generation and diffusion are presented in the paper. Because the laser is applied to the backside of the substrate, the damage due to the laser heat can be significantly reduced. The quality and efficient of the backside processing is better than those of the front side processing. The proposed techniques have great potential to provide an improved solution for glass cleaning.

  1. Brain lesion induced by 1319nm laser radiation

    NASA Astrophysics Data System (ADS)

    Yang, Zaifu; Chen, Hongxia; Wang, Jiarui; Chen, Peng; Ma, Ping; Qian, Huanwen

    2010-11-01

    The laser-tissue interaction has not been well defined at the 1319 nm wavelength for brain exposure. The goal of this research effort was to identify the behavioral and histological changes of brain lesion induced by 1319 nm laser. The experiment was performed on China Kunming mice. Unilateral brain lesions were created with a continuous-wave Nd:YAG laser (1319nm). The brain lesions were identified through behavioral observation and histological haematoxylin and eosin (H&E) staining method. The behavior change was observed for a radiant exposure range of 97~773 J/cm2. The histology of the recovery process was identified for radiant exposure of 580 J/cm2. Subjects were sacrificed 1 hour, 1 week, 2 weeks, 3 months, 7 months and 13 months after laser irradiation. Results showed that after laser exposure, behavioral deficits, including kyphosis, tail entasia, or whole body paralysis could be noted right after the animals recovered from anesthesia while gradually disappeared within several days and never recurred again. Histologically, the laser lesion showed a typical architecture dependent on the interval following laser treatment. The central zone of coagulation necrosis is not apparent right after exposure but becomes obvious within several days. The nerotic tissue though may persist for a long time, will finally be completely resorbed. No carbonization granules formed under our exposure condition.

  2. Laser induced breakdown spectroscopy application in joint European torus

    NASA Astrophysics Data System (ADS)

    Semerok, A.; L'Hermite, D.; Weulersse, J.-M.; Lacour, J.-L.; Cheymol, G.; Kempenaars, M.; Bekris, N.; Grisolia, C.

    2016-09-01

    The results on the first successful application of Laser Induced Breakdown Spectroscopy (LIBS) for remote in situ diagnostics of plasma facing components (a deposited layer on a divertor tile) in Joint European Torus (JET) are presented. The studies were performed with an available JET EDGE LIDAR laser system. For in-depth analysis of deposited layers on JET divertor tiles, a number of laser shots were applied onto the same divertor place without laser beam displacement. The spectral lines of D, CII and impurity elements (CrI, BeII, …) were identified in a wide spectral range (400-670 nm). With the increase in a number of laser shots applied onto the same divertor place, we observed consecutive changes in spectral line intensities of deuterium, carbon, and impurities with the appearance of spectral lines of tungsten substrate (WI). In-depth analysis of deposited layers on JET divertor tiles was made on the basis of the spectral line behaviour in reference to the applied laser shots. The possibility of surface cartography with laser beam displacement on the tile surface was demonstrated as well. Based on the results obtained, we may conclude that LIBS method is applicable for in situ remote analysis of deposited layers of JET plasma facing components.

  3. Laser-induced breakdown spectroscopy enhanced by a micro torch.

    PubMed

    Liu, L; Huang, X; Li, S; Lu, Yao; Chen, K; Jiang, L; Silvain, J F; Lu, Y F

    2015-06-01

    A commercial butane micron troch was used to enhance plasma optical emissions in laser-induced breakdown spectroscopy (LIBS). Fast imaging and spectroscopic analyses were used to observe plasma evolution in the atmospheric pressure for LIBS without and with using a micro torch. Optical emission intensities and signal-to-noise ratios (SNRs) as functions of delay time were studied. Enhanced optical emission and SNRs were obtained by using a micro torch. The effects of laser pulse energy on the emission intensities and SNRs were studied. The same spectral intensity could be obtained using micro torch with much lower laser pulse energy. The investigation of SNR evolution with delay time at different laser pulse energies showed that the SNR enhancement factor is higher for plasmas generated by lower laser pulse energies than those generated by higher laser energies. The calibration curves of emission line intensities with elemental concentrations showed that detection sensitivities of Mn I 404.136 nm and V I 437.923 nm were improved by around 3 times. The limits of detection for both Mn I 404.136 nm and V I 437.923 nm are reduced from 425 and 42 ppm to 139 and 20 ppm, respectively, after using the micro torch. The LIBS system with micro torch was demonstrated to be cost-effective, compact, and capable of sensitivity improvement, especially for LIBS system operating with low laser pulse energy. PMID:26072861

  4. The stochastic nature of growth of laser-induced damage

    NASA Astrophysics Data System (ADS)

    Carr, C. W.; Cross, David A.; Liao, Zhi M.; Norton, Mary A.; Negres, Raluca A.

    2015-07-01

    Laser fluence and operational tempo of ICF systems operating in the UV are typically limited by the growth of laser- induced damage on their final optics (primarily silica optics). In the early 2000 time frame, studies of laser damage growth with relevant large area beams revealed that for some laser conditions damage sites located on the exit surface of a fused silica optic grew following an exponential growth rule: D(n) = D0 exp (n α(φ)), where D is final site diameter, D0 is the initial diameter of the site, φ is the laser fluence, α(φ) is the growth coefficient, and n is the number of exposures. In general α is a linear function of φ, with a threshold of φTH. In recent years, it has been found that that growth behavior is actually considerably more complex. For example, it was found that α is not a constant for a given fluence but follows a probability distribution with a mean equal to α(φ). This is complicated by observations that these distributions are actually functions of the pulse shape, damage site size, and initial morphology of damage initiation. In addition, there is not a fixed fluence threshold for damage sites growth, which is better described by a probability of growth which depends on site size, morphology and laser fluence. Here will review these findings and discuss implications for the operation of large laser systems.

  5. IKK2 Inhibition Attenuates Laser-Induced Choroidal Neovascularization

    PubMed Central

    Lu, Huayi; Lu, Qingxian; Gaddipati, Subhash; Kasetti, Ramesh Babu; Wang, Wei; Pasparakis, Manolis; Kaplan, Henry J.; Li, Qiutang

    2014-01-01

    Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-κB pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either Ikk2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding Ikk2−/flox mice with Nestin-Cre mice. Deletion of Ikk2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-κB signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD. PMID:24489934

  6. Laser-Induced Spatiotemporal Dynamics of Magnetic Films.

    PubMed

    Shen, Ka; Bauer, Gerrit E W

    2015-11-01

    We present a theory for the coherent magnetization dynamics induced by a focused ultrafast laser beam in magnetic films, taking into account nonthermal (inverse Faraday effect) and thermal (heating) actuation. The dynamic conversion between spin waves and phonons is induced by the magnetoelastic coupling that allows efficient propagation of angular momentum. The anisotropy of the magnetoelastic coupling renders characteristic angle dependences of the magnetization propagation that are strikingly different for thermal and nonthermal actuation.

  7. Laser-Induced Spatiotemporal Dynamics of Magnetic Films.

    PubMed

    Shen, Ka; Bauer, Gerrit E W

    2015-11-01

    We present a theory for the coherent magnetization dynamics induced by a focused ultrafast laser beam in magnetic films, taking into account nonthermal (inverse Faraday effect) and thermal (heating) actuation. The dynamic conversion between spin waves and phonons is induced by the magnetoelastic coupling that allows efficient propagation of angular momentum. The anisotropy of the magnetoelastic coupling renders characteristic angle dependences of the magnetization propagation that are strikingly different for thermal and nonthermal actuation. PMID:26588408

  8. Analysis of organic vapors with laser induced breakdown spectroscopy

    SciTech Connect

    Nozari, Hadi; Tavassoli, Seyed Hassan; Rezaei, Fatemeh

    2015-09-15

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  9. Supersonic laser-induced jetting of aluminum micro-droplets

    NASA Astrophysics Data System (ADS)

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-01

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10-100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  10. Analysis of organic vapors with laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Nozari, Hadi; Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2015-09-01

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  11. Laser-induced macular holes demonstrate impaired choroidal perfusion

    NASA Astrophysics Data System (ADS)

    Brown, Jeremiah, Jr.; Allen, Ronald D.; Zwick, Harry; Schuschereba, Steven T.; Lund, David J.; Stuck, Bruce E.

    2003-06-01

    Choroidal perfusion was evaluated following the creation of a laser induced macular hole in a nonhuman primate model. Two Rhesus monkeys underwent macular exposures delivered by a Q-switched Nd:YAG laser. The lesions were evaluated with fluorescein angiography and indocyanine green (ICG) angiography . Each lesion produced vitreous hemorrhage and progressed to a full thickness macular hole. ICG angiography revealed no perfusion of the choriocapillaris beneath the lesion centers. Histopathologic evaluation showed replacement of the choriocapillaris with fibroblasts and connective tissue. Nd:YAG, laser-induced macular holes result in long term impairment of choroidal perfusion at the base of the hole due to choroidal scarring and obliteration of the choriocapillaris.

  12. Femtosecond laser pulse induced desorption: A molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Lončarić, Ivor; Alducin, Maite; Saalfrank, Peter; Juaristi, J. Iñaki

    2016-09-01

    In recent simulations of femtosecond laser induced desorption of molecular oxygen from the Ag(110) surface, it has been shown that depending on the properties (depth and electronic environment) of the well in which O2 is adsorbed, the desorption can be either induced dominantly by hot electrons or via excitations of phonons. In this work we explore whether the ratios between the desorption yields from different adsorption wells can be tuned by changing initial surface temperature and laser pulse properties. We show that the initial surface temperature is an important parameter, and that by using low initial surface temperatures the electronically mediated process can be favored. In contrast, laser properties seem to have only a modest influence on the results.

  13. Supersonic laser-induced jetting of aluminum micro-droplets

    SciTech Connect

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-04

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  14. Experimental Studies of Laser-Induced Breakdown in Transparent Dielectrics

    SciTech Connect

    Carr, C W

    2003-09-23

    The mechanisms by which transparent dielectrics damage when exposed to high power laser radiation has been of scientific and technological interest since the invention of the laser. In this work, a set of three experiments are presented which provide insight into the damage initiation mechanisms and the processes involved in laser-induced damage. Using an OPO (optical parametric oscillator) laser, we have measured the damage thresholds of deuterated potassium dihydrogen phosphate (DKDP) from the near ultraviolet into the visible. Distinct steps, whose width is of order K{sub b}T, are observed in the damage threshold at photon energies associated with the number of photons (3{yields}2 or 4{yields}3) needed to promote a ground state electron across the energy gap. The wavelength dependence of the damage threshold suggests that a primary mechanism for damage initiation in DKDP is a multi-photon process in which the order is reduced through excited defect state absorption. In-situ fluorescence microscopy, in conjunction with theoretical calculations by Liu et al., has been used to establish that hydrogen displacement defects are potentially responsible for the reduction in the multi-photon cross-section. During the damage process, the material absorbs energy from the laser pulse and produces an ionized region that gives rise to broadband emission. By performing a time-resolved investigation of this emission, we demonstrate both that it is blackbody in nature, and we provide the first direct measurement of the localized temperature during and following laser damage initiation for various optical materials. For excitation using nanosecond laser pulses, the plasma, when confined in the bulk, is in thermal equilibrium with the lattice. These results allow for a detailed characterization of temperature, pressure, and electron densities occurring during laser-induced damage.

  15. Glaucoma Diagnosis and Monitoring Using Advanced Imaging Technologies

    PubMed Central

    Sehi, Mitra; Iverson, Shawn M

    2014-01-01

    Advanced ocular imaging technologies facilitate objective and reproducible quantification of change in glaucoma but at the same time, impose new challenges on scientists and clinicians for separating true structural change from imaging noise. This review examines time-domain and spectral-domain optical coherence tomography, confocal scanning laser ophthalmoscopy and scanning laser polarimetry technologies and discusses the diagnostic accuracy and the ability of each technique for evaluation of glaucomatous progression. A broad review of the current literature reveals that objective assessment of retinal nerve fiber layer, ganglion cell complex and optic nerve head topography may improve glaucoma monitoring when used as a complementary tool in conjunction with the clinical judgment of an expert. PMID:24470807

  16. Using Laser-Induced Incandescence To Measure Soot in Exhaust

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.; Sankar, Subramanian V.

    2005-01-01

    An instrumentation system exploits laser-induced incandescence (LII) to measure the concentration of soot particles in an exhaust stream from an engine, furnace, or industrial process that burns hydrocarbon fuel. In comparison with LII soot-concentration-measuring systems, this system is more complex and more capable.

  17. Laser-Induced Breakdown Spectroscopy of Trace Metals

    NASA Technical Reports Server (NTRS)

    Simons, Stephen (Technical Monitor); VanderWal, Randall L.; Ticich, Thomas M.; West, Joseph R., Jr.

    2004-01-01

    An alternative approach for laser-induced breakdown spectroscopy (LIBS) determination of trace metal determination in liquids is demonstrated. The limits of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for 15 metals metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) tested.

  18. Laser-induced copper deposition with weak reducing agents

    NASA Astrophysics Data System (ADS)

    Kochemirovsky, V. A.; Fateev, S. A.; Logunov, L. S.; Tumkin, I. I.; Safonov, S. V.; Khairullina, E. M.

    2013-11-01

    The study showed that organic alcohols with 1,2,3,5,6 hydroxyl groups can be used as reducing agents for laser-induced copper deposition from solutions (LCLD).Multiatomic alcohols, sorbitol, xylitol, and glycerol, are shown to be effective reducing agents for performing LCLD at glass-ceramic surfaces. High-conductivity copper tracks with good topology were synthesized.

  19. Shock pressures induced in condensed matter by laser ablation

    NASA Astrophysics Data System (ADS)

    Swift, Damian C.; Tierney, Thomas E.; Kopp, Roger A.; Gammel, J. Tinka

    2004-03-01

    The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m2. States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery.

  20. Antioxidant Treatment Limits Neuroinflammation in Experimental Glaucoma

    PubMed Central

    Yang, Xiangjun; Hondur, Gözde; Tezel, Gülgün

    2016-01-01

    Purpose Besides primary neurotoxicity, oxidative stress may compromise the glial immune regulation and shift the immune homeostasis toward neurodegenerative inflammation in glaucoma. We tested this hypothesis through the analysis of neuroinflammatory and neurodegenerative outcomes in mouse glaucoma using two experimental paradigms of decreased or increased oxidative stress. Methods The first experimental paradigm tested the effects of Tempol, a multifunctional antioxidant, given through osmotic mini-pumps for drug delivery by constant infusion. Following a 6-week treatment period after microbead/viscoelastic injection-induced ocular hypertension, retina and optic nerve samples were analyzed for markers of oxidative stress and cytokine profiles using specific bioassays. We also analyzed a redox-sensitive transcriptional regulator of neuroinflammation, namely NF-κB. The second paradigm included a similar analysis of the effects of overloaded oxidative stress on retina and optic nerve inflammation in mice knockout for a major antioxidant enzyme (SOD1−/−). Results Increased antioxidant capacity and decreased protein carbonyls and HNE adducts with Tempol treatment verified the drug delivery and biological function. Among a range of cytokines measured, proinflammatory cytokines, including IL-1, IL-2, IFN-γ, and TNF-α, exhibited more than 2-fold decreased titers in Tempol-treated ocular hypertensive eyes. Antioxidant treatment also resulted in a prominent decrease in NF-κB activation in the ocular hypertensive retina and optic nerve. Although pharmacological treatment limiting the oxidative stress resulted in decreased neuroinflammation, ocular hypertension–induced neuroinflammatory responses were increased in SOD1−/− mice with defective antioxidant response. Conclusions These findings support the oxidative stress–related mechanisms of neuroinflammation and the potential of antioxidant treatment as an immunomodulation strategy for neuroprotection in

  1. Semiconductor laser asymmetry cutting glass with laser induced thermal-crack propagation

    NASA Astrophysics Data System (ADS)

    Zhao, Chunyang; Zhang, Hongzhi; Wang, Yang

    2014-12-01

    Laser induced thermal-crack propagation (LITP) makes the material to produce an uneven temperature field, maximum temperature can't soften or melt the material, induces the thermal stress, then the crack separates along the cutting path. One of the problems in laser asymmetry cutting glass with LITP is the cutting deviation along scanning trajectory. This study lays great emphasis on considering the dynamic extension of crack to explain the reason of the cutting deviation in laser asymmetry cutting glass, includes asymmetric linear cutting and a quarter of a circular curve cutting. This paper indicates the experiments of semiconductor laser asymmetry cutting glass with LITP. Optical microscope photographs of the glass sheet are obtained to examine the cutting deviation. The extended finite element method (XFEM) is used to simulate the dynamic propagation of crack; the crack path does not have to be specified a priori. The cutting deviation mechanism and the crack propagation process are studied by the stress fields using finite element software ABAQUS. This work provides a theoretical basis to investigate the cutting deviation in laser asymmetry cutting glass. In semiconductor laser asymmetry cutting glass, the tensile stress is the basis of crack propagation, then the compressive stress not only makes the crack to extend stably, but also controls the direction of crack propagation.

  2. The fluence threshold of femtosecond laser blackening of metals: The effect of laser-induced ripples

    NASA Astrophysics Data System (ADS)

    Ou, Zhigui; Huang, Min; Zhao, Fuli

    2016-05-01

    With the primary controlling factor of the laser fluence, we have investigated femtosecond laser blackening of stainless steel, brass, and aluminum in visible light range. In general, low reflectance about 5% can be achieved in appropriate ranges of laser fluences for all the treated metal surfaces. Significantly, towards stainless steel and brass a fluence threshold of blackening emerges unusually: a dramatic reflectance decline occurs in a specific, narrow fluence range. In contrast, towards aluminum the reflectance declines steadily over a wide fluence range instead of the threshold-like behavior from steel and brass. The morphological characteristics and corresponding reflectance spectra of the treated surfaces indicates that the blackening threshold of stainless steel and brass corresponds to the fluence threshold of laser-induced subwavelength ripples. Such periodic ripples growing rapidly near ablation threshold absorb visible light efficiently through grating coupling and cavity trapping promoted by surface plasmon polaritons. Whereas, for aluminum, with fluence increasing the looming ripples are greatly suppressed by re-deposited nanoparticle aggregates that present intrinsic colors other than black, and until the formation of large scale "ravines" provided with strong light-trapping, sufficient blackening is achieved. In short, there are different fluence dependencies for femtosecond laser blackening of metals, and the specific blackening fluence threshold for certain metals in the visible range originates in the definite fluence threshold of femtosecond laser-induced ripples.

  3. Cataract Surgery in the Glaucoma Patient

    PubMed Central

    Kung, Jennifer S.; Choi, Daniel Y.; Cheema, Anjum S.; Singh, Kuldev

    2015-01-01

    To summarize the role of cataract surgery in the glaucoma patient, in terms of the effect on intraocular pressure (IOP) as well as diagnostic and therapeutic considerations for those with both conditions. Recent evidence suggests that cataract extraction may produce a significant and sustained IOP reduction in individuals with open-angle glaucoma, ocular hypertension, and angle-closure glaucoma. Cataract removal may improve the practitioner's ability to interpret perimetric testing, and re-establishing perimetric and optic nerve imaging baselines is recommended after cataract surgery. The sequence of cataract surgery relative to glaucoma surgery impacts the likelihood of complications and surgical success. There are multiple benefits to perform cataract surgery prior to glaucoma surgery while cataract surgery after trabeculectomy increases the risk of subsequent filtration failure. As “minimally invasive glaucoma surgeries” continue to improve in terms of efficacy, there is an evolving role for combined cataract and glaucoma surgery in patients with early to moderate stages of glaucoma. PMID:25624668

  4. Dry Eyes and Glaucoma: Double Trouble

    MedlinePlus

    ... Size Small Text Medium Text Large Text Contrast Dark on Light Light on Dark Donate Search Menu Donate What is Glaucoma? Care ... Low Vision Resources Medication Guide Resources on the Web » See All Articles Help the Cause Glaucoma affects ...

  5. Update on Minimally Invasive Glaucoma Surgery (MIGS) and New Implants

    PubMed Central

    Brandão, Lívia M.; Grieshaber, Matthias C.

    2013-01-01

    Traditional glaucoma surgery has been challenged by the advent of innovative techniques and new implants in the past few years. There is an increasing demand for safer glaucoma surgery offering patients a timely surgical solution in reducing intraocular pressure (IOP) and improving their quality of life. The new procedures and devices aim to lower IOP with a higher safety profile than fistulating surgery (trabeculectomy/drainage tubes) and are collectively termed “minimally invasive glaucoma surgery (MIGS).” The main advantage of MIGS is that they are nonpenetrating and/or bleb-independent procedures, thus avoiding the major complications of fistulating surgery related to blebs and hypotony. In this review, the clinical results of the latest techniques and devices are presented by their approach, ab interno (trabeculotomy, excimer laser trabeculotomy, trabecular microbypass, suprachoroidal shunt, and intracanalicular scaffold) and ab externo (canaloplasty, Stegmann Canal Expander, suprachoroidal Gold microshunt). The drawback of MIGS is that some of these procedures produce a limited IOP reduction compared to trabeculectomy. Currently, MIGS is performed in glaucoma patients with early to moderate disease and preferably in combination with cataract surgery. PMID:24369494

  6. Canaloplasty: A Minimally Invasive and Maximally Effective Glaucoma Treatment

    PubMed Central

    Khaimi, Mahmoud A.

    2015-01-01

    Canaloplasty is a highly effective, minimally invasive, surgical technique indicated for the treatment of open-angle glaucoma that works by restoring the function of the eye's natural outflow system. The procedure's excellent safety profile and long-term efficacy make it a viable option for the majority of glaucoma patient types. It can be used in conjunction with existing drug based glaucoma treatments, after laser or other types of incisional surgery, and does not preclude or affect the outcome of future surgery. Numerous scientific studies have shown Canaloplasty to be safe and effective in lowering IOP whilst reducing medication dependence. A recent refinement of Canaloplasty, known as ab-interno Canaloplasty (ABiC), maintains the IOP-lowering and safety benefits of traditional (ab-externo) Canaloplasty using a more efficient, simplified surgical approach. This paper presents a review of Canaloplasty indications, clinical data, and complications, as well as comparisons with traditional incisional glaucoma techniques. It also addresses the early clinical evidence for ABiC. PMID:26495135

  7. Update on Minimally Invasive Glaucoma Surgery (MIGS) and New Implants.

    PubMed

    Brandão, Lívia M; Grieshaber, Matthias C

    2013-01-01

    Traditional glaucoma surgery has been challenged by the advent of innovative techniques and new implants in the past few years. There is an increasing demand for safer glaucoma surgery offering patients a timely surgical solution in reducing intraocular pressure (IOP) and improving their quality of life. The new procedures and devices aim to lower IOP with a higher safety profile than fistulating surgery (trabeculectomy/drainage tubes) and are collectively termed "minimally invasive glaucoma surgery (MIGS)." The main advantage of MIGS is that they are nonpenetrating and/or bleb-independent procedures, thus avoiding the major complications of fistulating surgery related to blebs and hypotony. In this review, the clinical results of the latest techniques and devices are presented by their approach, ab interno (trabeculotomy, excimer laser trabeculotomy, trabecular microbypass, suprachoroidal shunt, and intracanalicular scaffold) and ab externo (canaloplasty, Stegmann Canal Expander, suprachoroidal Gold microshunt). The drawback of MIGS is that some of these procedures produce a limited IOP reduction compared to trabeculectomy. Currently, MIGS is performed in glaucoma patients with early to moderate disease and preferably in combination with cataract surgery.

  8. Evaluation of Hemodynamic Parameters as Predictors of Glaucoma Progression

    PubMed Central

    Janulevičiene, Ingrida; Ehrlich, Rita; Siesky, Brent; Nedzelskienė, Irena; Harris, Alon

    2011-01-01

    Purpose. To evaluate hemodynamic parameters as possible predictors for glaucoma progression. Methods. An 18-month randomized double-masked cohort study including 30 open-angle glaucoma patients receiving fixed-combination treatment with Dorzolamide/Timolol (DTFC) or Latanoprost/Timolol (LTFC) (n = 15 per group) was performed. Intraocular pressure (IOP), arterial blood pressure (BP), ocular and diastolic perfusion pressures (OPP, DPP), color Doppler imaging, pulsatile ocular blood flow analysis, scanning laser polarimetry, and Humphrey visual field evaluations were included. Results. Both treatments showed statistically similar IOP reduction. Six patients in DTFC and 7 in LTFC group met glaucoma progression criteria. DTFC group had higher OPP, DPP, and lower vascular resistivity indices as compared to the LTFC. Progressing patients had higher nerve fiber index, lower systolic BP, OPP, DPP, higher ophthalmic and central retinal artery vascular resistance, and lower pulse volume (P < .05; t-test). Conclusions. Structural changes consistent with glaucoma progression correlate with non-IOP-dependent risk factors. PMID:21577269

  9. Laser-induced damage of multilayer dielectric gratings with picosecond laser pulses under vacuum and air

    NASA Astrophysics Data System (ADS)

    Kong, Fanyu; Jin, Yunxia; Huang, Haopeng; Zhang, Hong; Liu, Shijie; He, Hongbo

    2015-10-01

    In this study, laser damage tests of multilayer dielectric gratings (MDGs) are performed in vacuum (5×10-4 Pa) and in air at a wavelength of 1053 nm with pulse widths of 0.56 ps ~9.7 ps. The laser-induced damage threshold (LIDT) of MDGs in vacuum/air ranges from 2.1/2.2 J/cm2 to 4.4/4.8 J/cm2 for laser beams of normal incidence. The LIDT of MDGs follows a τ0.26 scaling in the pulse width regime considered. The typical damage morphologies in the two environments caused by the near threshold pulse were observed using a scanning electron microscope (SEM); the results indicate that the damage features of MDGs in vacuum are the same as those in air. The testing results reveal that a clean vacuum environment neither changes the laser damage mechanism nor lowers the LIDT of MDGs.

  10. Ex-PRESS mini glaucoma shunt: surgical technique and review of clinical experience.

    PubMed

    Hendrick, Andrew M; Kahook, Malik Y

    2008-11-01

    Glaucoma is a leading cause of worldwide blindness. Treatment of this chronic disease, centered on lowering intraocular pressure (IOP), may require surgical intervention when medical and/or laser therapy fail to control IOP. Traditional glaucoma surgery, such as trabeculectomy, has been performed for decades and has a proven track record of success. Unfortunately, many complications such as hypotony and slow visual recovery are known to occur and can lead to significant patient morbidity. New devices are being developed to allow surgeons increased control with more predictable postoperative results. One such device, the Ex-PRESS mini glaucoma shunt, has undergone changes in design and method of insertion making it more appealing for use in patients requiring IOP-lowering surgery. We summarize pertinent literature and expand on the future role of this device in glaucoma surgery. PMID:19025342

  11. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization.

    PubMed

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M; Gordon, Reuven; Choi, Byoung C

    2015-01-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1 mJ/cm(2) due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording. PMID:26515296

  12. Laser induced damage in optical materials: 7th ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1976-06-01

    The Seventh ERDA-ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado, on 29-31 July 1975. These Symposia are held as part of the activities in ASTM Subcommittee II on Lasers and Laser Materials, which is charged with the responsibilities of formulating standards and test procedures for laser materials, components, and devices. The Chairman of Subcommittee II is Haynes Lee, of Owens-Illinois, Inc. Co-chairmen for the Damage Symposia are Arthur Guenther of the Air Force Weapons Laboratory and Alexander J. Glass of Law-rence Livermore Laboratory. Over 150 attendees at the Symposium heard forty-five papers on topics relating fabrication procedures to laser induced damage in optical materials; on metal mirrors; in ir window materials; the multipulse, wavelength, and pulse length dependence of damage thresholds; damage in dielectric films and at exposed surfaces; as well as theoretical discussions on avalanche ionization and multiphoton processes of importance at shorter wavelengths. Of particular importance were the scaling relations developed from several parametric studies relating fundamental properties (refractive index, surface roughness etc.) to the damage threshold. This year many of the extrinsic influences tending to reduce a materials damage resistance were isolated such that measures of their egregious nature could be quantified. Much still needs to be accomplished to improve processing and fabrication procedures to allow a measurable approach to a materials intrinsic strength to be demonstrated.

  13. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization

    PubMed Central

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M.; Gordon, Reuven; Choi, Byoung C.

    2015-01-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1 mJ/cm2 due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording. PMID:26515296

  14. Laser Induced Damage in Optical Materials: 6th ASTM Symposium.

    PubMed

    Glass, A J; Guenther, A H

    1975-03-01

    The Sixth ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado on 22-23 May 1974. Over 150 attendees at the Symposium heard thirty-one papers on topics relating to laser induced damage in crystalline and nonlinear optical materials, at dielectric surfaces, and in thin film coatings as well as discussions of damage problems in the ir region due both to cw and pulsed irradiation. In addition, several reports on the theoretical analysis of laser-materials interaction relative to the damage progress were given, along with tabulations of fundamental materials properties of importance in evaluation of optical material response to high-power laser radiation. Attention was given to high-power laser system design considerations that relate to improved system performance and reliability when various damage mechanisms are operable in such systems. A workshop on the machining of optics was held, and nine papers on various facets of the topic were presented dealing with machining procedures, surface characterization of machined elements, coating of machined components, and the polishing and damage resistance of polished, coated, and bare metal reflectors. PMID:20134954

  15. Outcomes of Ahmed valve surgery for refractory glaucoma in Dhahran, Saudi Arabia

    PubMed Central

    Alasbali, Tariq; Alghamdi, Abdullah Ali; Khandekar, Rajiv

    2015-01-01

    AIM To evaluate the outcomes of Ahmed glaucoma valve (AGV) implantation surgery for refractory glaucoma. METHODS This one-armed historical cohort study was conducted in 2011. Refractory glaucoma was defined as eyes with an intraocular pressure (IOP) greater than 21 mm Hg with maximally tolerated glaucoma medications, failed surgeries, or both. For all eyes with refractory glaucoma that underwent AGV implantation, data were collected on IOP, the best corrected visual acuity (BCVA) and glaucoma medications preoperatively and 4, 6, 12, 24 and 56wk postoperatively. Logarithm values of IOP were calculated and compared. RESULTS The study group was comprised of 30 patients (30 eyes, 16 males and 14 females) with refractory glaucoma. Mean preoperative IOP was 39.3±13.8 mm Hg. Postoperative mean IOP was 15.7±7.1 mm Hg, 19.6±12.8 mm Hg and 13.9±14.2 mm Hg at 12, 24 and 56wk respectively. BCVA was ≥ 6/60 in 11 eyes preoperatively, and five eyes had BCVA≥6/60 at 56wk postoperatively. Preoperatively, more than four medications were used to treat glaucoma in 21 eyes. At 12wk postoperatively, no medications were required to control IOP in 20 eyes. At 56wk postoperatively, at least one medication was required to control IOP in 10 eyes. Over the entire follow up period, four eyes were treated with yttrium aluminium garnet (YAG) laser and 14 eyes required a second surgery. The AGV was removed in four eyes. CONCLUSION AGV implantation reduced IOP and the number of medications required to control refractory glaucoma. However, there was a higher risk of decreased vision. Long-term follow up and prompt intervention are recommended. PMID:26086008

  16. Radioiodine detector based on laser induced fluorescence

    DOEpatents

    McDonald, Jimmie R.; Baronavski, Andrew P.

    1980-01-01

    The invention involves the measurement of the concentration of the radioisotope .sup.129 I.sub.2 in the presence of a gas. The invention uses a laser to excite a sample of the .sup.129 I.sub.2 in a sample gas chamber and a reference sample of a known concentration of .sup.129 I.sub.2 in a reference gas chamber. The .sup.129 I.sub.2 in the sample and reference gas chamber each gives off fluorescence emissions which are received by photomultipliers which provide signals to a detector. The detector uses a ratioing technique to determine the concentration of .sup.129 I.sub.2 in the sample gas chamber.

  17. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1990-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neturons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  18. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1991-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  19. Momentum induced by laser-tissue interaction

    SciTech Connect

    Dingus, R.S.

    1993-01-01

    Impulsive momentum is imparted to residual tissue during pulsed-laser ablation because the moss ablated is generally ejected with a sizable velocity. Accurate measurements of the impulse are possible, which can provide an important monitor of the ablation process. Simple models can be used to predict the impulse under a variety of conditions; in some cases, complex radiation-hydrodynamic code calculations are required. In this paper, this modeling is discussed along with the dependence of momentum on the pulsed heating and target conditions. Momentum measurement techniques are discussed briefly. The behavior is explained in terms of dimensionless parameters and the impulse coupling coefficient as a function of incident fluence, which has a well defined threshold as well as a maximum. Complications in the mixed liquid-vapor phase are also addressed.

  20. Momentum induced by laser-tissue interaction

    SciTech Connect

    Dingus, R.S.

    1993-04-01

    Impulsive momentum is imparted to residual tissue during pulsed-laser ablation because the moss ablated is generally ejected with a sizable velocity. Accurate measurements of the impulse are possible, which can provide an important monitor of the ablation process. Simple models can be used to predict the impulse under a variety of conditions; in some cases, complex radiation-hydrodynamic code calculations are required. In this paper, this modeling is discussed along with the dependence of momentum on the pulsed heating and target conditions. Momentum measurement techniques are discussed briefly. The behavior is explained in terms of dimensionless parameters and the impulse coupling coefficient as a function of incident fluence, which has a well defined threshold as well as a maximum. Complications in the mixed liquid-vapor phase are also addressed.

  1. Modeling of Laser Induced Damage in NIF UV Optics

    SciTech Connect

    Feit, M D; Rubenchik, A M

    2001-02-21

    Controlling damage to nominally transparent optical elements such as lenses, windows and frequency conversion crystals on high power lasers is a continuing technical problem. Scientific understanding of the underlying mechanisms of laser energy absorption, material heating and vaporization and resultant mechanical damage is especially important for UV lasers with large apertures such as NIF. This LDRD project was a single year effort, in coordination with associated experimental projects, to initiate theoretical descriptions of several of the relevant processes. In understanding laser damage, we distinguish between damage initiation and the growth of existent damage upon subsequent laser irradiation. In general, the effect of damage could be ameliorated by either preventing its initiation or by mitigating its growth. The distinction comes about because initiation is generally due to extrinsic factors such as contaminants, which provide a means of local laser energy absorption. Thus, initiation tends to be local and stochastic in nature. On the other hand, the initial damaging event appears to modify the surrounding material in such a way that multiple pulse damage grows more or less regularly. More exactly, three ingredients are necessary for visible laser induced damage. These are adequate laser energy, a mechanism of laser energy absorption and mechanical weakness. For damage growth, the material surrounding a damage site is already mechanically weakened by cracks and probably chemically modified as well. The mechanical damage can also lead to electric field intensification due to interference effects, thus increasing the available laser energy density. In this project, we successfully accounted for the pulselength dependence of damage threshold in bulk DKDP crystals with the hypothesis of small absorbers with a distribution of sizes. We theoretically investigated expected scaling of damage initiation craters both to baseline detailed numerical simulations

  2. Laser frequency locking based on Rydberg electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Yuechun, Jiao; Jingkui, Li; Limei, Wang; Hao, Zhang; Linjie, Zhang; Jianming, Zhao; Suotang, Jia

    2016-05-01

    We present a laser frequency locking to Rydberg transition with electromagnetically induced transparency (EIT) spectra in a room-temperature cesium vapor cell. Cesium levels 6S1/2, 6P3/2, and the nD5/2 state, compose a cascade three-level system, where a coupling laser drives Rydberg transition, and probe laser detects the EIT signal. The error signal, obtained by demodulating the EIT signal, is used to lock the coupling laser frequency to Rydberg transition. The laser frequency fluctuation, ∼0.7 MHz, is obtained after locking on, with the minimum Allan variance to be 8.9 × 10‑11. This kind of locking method can be used to stabilize the laser frequency to the excited transition. Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the National Natural Science Foundation of China (Grants Nos. 11274209, 61475090, 61378039, and 61378013), and the Research Project Supported by Shanxi Scholarship Council of China (Grant No. 2014-009).

  3. Laser frequency locking based on Rydberg electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Yuechun, Jiao; Jingkui, Li; Limei, Wang; Hao, Zhang; Linjie, Zhang; Jianming, Zhao; Suotang, Jia

    2016-05-01

    We present a laser frequency locking to Rydberg transition with electromagnetically induced transparency (EIT) spectra in a room-temperature cesium vapor cell. Cesium levels 6S1/2, 6P3/2, and the nD5/2 state, compose a cascade three-level system, where a coupling laser drives Rydberg transition, and probe laser detects the EIT signal. The error signal, obtained by demodulating the EIT signal, is used to lock the coupling laser frequency to Rydberg transition. The laser frequency fluctuation, ˜0.7 MHz, is obtained after locking on, with the minimum Allan variance to be 8.9 × 10-11. This kind of locking method can be used to stabilize the laser frequency to the excited transition. Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the National Natural Science Foundation of China (Grants Nos. 11274209, 61475090, 61378039, and 61378013), and the Research Project Supported by Shanxi Scholarship Council of China (Grant No. 2014-009).

  4. Low intensity infrared laser induces filamentation in Escherichia coli cells

    NASA Astrophysics Data System (ADS)

    Fonseca, A. S.; Presta, G. A.; Geller, M.; Paoli, F.

    2011-10-01

    Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the photobiological basis is not well understood. The aim of this wok was to evaluate, using bacterial filamentation assay, effects of laser on Escherichia coli cultures in exponential and stationary growth phase. E. coli cultures, proficient and deficient on DNA repair, in exponential and stationary growth phase, were exposed to low intensity infrared laser, aliquots were spread onto microscopic slides, stained by Gram method, visualized by optical microscopy, photographed and percentage of bacterial filamentation were determined. Low intensity infrared laser with therapeutic fluencies and different emission modes can induce bacterial filamentation in cultures of E. coli wild type, fpg/ mutM, endonuclease III and exonuclease III mutants in exponential and stationary growth phase. This study showed induction of bacterial, filamentation in E. coli cultures expose to low intensity infrared laser and attention to laser therapy protocols, which should take into account fluencies, wavelengths, tissue conditions, and genetic characteristics of cells before beginning treatment.

  5. Femtosecond laser-induced periodic surface structures on silica

    SciTech Connect

    Hoehm, S.; Rosenfeld, A.; Krueger, J.; Bonse, J.

    2012-07-01

    The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused silica glass) upon irradiation in air with multiple linearly polarized single- and double-fs-laser pulse sequences ({tau} = 150 fs pulse duration, {lambda} = 800 nm center wavelength, temporal pulse separation {Delta}t < 40 ps) is studied experimentally and theoretically. Two distinct types of fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL)] with different spatial periods and orientations were identified. Their appearance was characterized with respect to the experimental parameters peak laser fluence and number of laser pulses per spot. Additionally, the 'dynamics' of the LIPSS formation was addressed in complementary double-fs-pulse experiments with varying delays, revealing a characteristic change of the LSFL periods. The experimental results are interpreted on the basis of a Sipe-Drude model considering the carrier dependence of the optical properties of fs-laser excited silica. This new approach provides an explanation of the LSFL orientation parallel to the laser beam polarisation in silica - as opposed to the behaviour of most other materials.

  6. Dynamics of laser-induced electroconvection pulses.

    PubMed

    Giebink, N C; Johnson, E R; Saucedo, S R; Miles, E W; Vardanyan, K K; Spiegel, D R; Allen, C C

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/degrees C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10-20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left (right) side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches approximately 0.3. We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  7. Dynamics of laser-induced electroconvection pulses

    NASA Astrophysics Data System (ADS)

    Giebink, N. C.; Johnson, E. R.; Saucedo, S. R.; Miles, E. W.; Vardanyan, K. K.; Spiegel, D. R.; Allen, C. C.

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/° C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10 20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left () side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches ˜0.3 . We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  8. Provider Education about Glaucoma and Glaucoma Medications during Videotaped Medical Visits.

    PubMed

    Sleath, Betsy; Blalock, Susan J; Carpenter, Delesha M; Muir, Kelly W; Sayner, Robyn; Lawrence, Scott; Giangiacomo, Annette L; Hartnett, Mary Elizabeth; Tudor, Gail; Goldsmith, Jason; Robin, Alan L

    2014-01-01

    Objective. The purpose of this study was to examine how patient, physician, and situational factors are associated with the extent to which providers educate patients about glaucoma and glaucoma medications, and which patient and provider characteristics are associated with whether providers educate patients about glaucoma and glaucoma medications. Methods. Patients with glaucoma who were newly prescribed or on glaucoma medications were recruited and a cross-sectional study was conducted at six ophthalmology clinics. Patients' visits were videotape recorded and patients were interviewed after visits. Generalized estimating equations were used to analyze the data. Results. Two hundred and seventy-nine patients participated. Providers were significantly more likely to educate patients about glaucoma and glaucoma medications if they were newly prescribed glaucoma medications. Providers were significantly less likely to educate African American patients about glaucoma. Providers were significantly less likely to educate patients of lower health literacy about glaucoma medications. Conclusion. Eye care providers did not always educate patients about glaucoma or glaucoma medications. Practice Implications. Providers should consider educating more patients about what glaucoma is and how it is treated so that glaucoma patients can better understand their disease. Even if a patient has already been educated once, it is important to reinforce what has been taught before. PMID:24868450

  9. Provider Education about Glaucoma and Glaucoma Medications during Videotaped Medical Visits

    PubMed Central

    Sleath, Betsy; Blalock, Susan J.; Carpenter, Delesha M.; Muir, Kelly W.; Sayner, Robyn; Lawrence, Scott; Giangiacomo, Annette L.; Hartnett, Mary Elizabeth; Tudor, Gail; Goldsmith, Jason; Robin, Alan L.

    2014-01-01

    Objective. The purpose of this study was to examine how patient, physician, and situational factors are associated with the extent to which providers educate patients about glaucoma and glaucoma medications, and which patient and provider characteristics are associated with whether providers educate patients about glaucoma and glaucoma medications. Methods. Patients with glaucoma who were newly prescribed or on glaucoma medications were recruited and a cross-sectional study was conducted at six ophthalmology clinics. Patients' visits were videotape recorded and patients were interviewed after visits. Generalized estimating equations were used to analyze the data. Results. Two hundred and seventy-nine patients participated. Providers were significantly more likely to educate patients about glaucoma and glaucoma medications if they were newly prescribed glaucoma medications. Providers were significantly less likely to educate African American patients about glaucoma. Providers were significantly less likely to educate patients of lower health literacy about glaucoma medications. Conclusion. Eye care providers did not always educate patients about glaucoma or glaucoma medications. Practice Implications. Providers should consider educating more patients about what glaucoma is and how it is treated so that glaucoma patients can better understand their disease. Even if a patient has already been educated once, it is important to reinforce what has been taught before. PMID:24868450

  10. Glaucoma - Multiple Languages: MedlinePlus

    MedlinePlus

    ... Glaucoma (Arabic) الجلوآوما - العربية Bilingual PDF Health Information Translations Chinese - Simplified (简体中文) Glaucoma 青光眼 - 简体中文 (Chinese - Simplified) Bilingual PDF Health Information Translations Glaucoma English 青光眼 - 简体中文 (Chinese - Simplified) PDF Chinese ...

  11. Laser-induced hybrid trap for microparticles

    NASA Astrophysics Data System (ADS)

    Wang, Yuzhu; Ni, H. Q.; Li, Yong Qing; Xu, Yuguang; Lu, Baolong; Shao, Wei

    1992-10-01

    This paper reports the observation of stable trapping of a transparent microparticle. The trap is a light induced hybrid one which consists of both light pressure force and fluid force. A theoretical analysis and experimental results are given. The possible applications are also discussed.

  12. Spatial confinement effects in laser-induced breakdown spectroscopy

    SciTech Connect

    Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F.

    2007-08-20

    The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.

  13. Laser-Induced Breakdown Spectroscopy (LIBS): specific applications

    NASA Astrophysics Data System (ADS)

    Trtica, M. S.; Savovic, J.; Stoiljkovic, M.; Kuzmanovic, M.; Momcilovic, M.; Ciganovic, J.; Zivkovic, S.

    2015-12-01

    A short overview of Laser Induced Breakdown Spectroscopy (LIBS) with emphasis on the new trends is presented. Nowadays, due to unique features of this technique, LIBS has found applications in a great variety of fields. Achievements in the application of LIBS in nuclear area, for hazardous materials detection and in geology were considered. Also, some results recently obtained at VINCA Institute, with LIBS system based on transversely excited atmospheric (TEA) CO2 laser, are presented. Future investigations of LIBS will be oriented toward further improvement of the analytical performance of this technique, as well as on finding new application fields.

  14. Laser induced fluorescence of biochemical for UV LIDAR application.

    PubMed

    Gupta, L; Sharma, R C; Razdan, A K; Maini, A K

    2014-05-01

    Laser induced fluorescence spectroscopy in the ultraviolet regime has been used for the detection of biochemical through a fiber coupled CCD detector from a distance of 2 m. The effect of concentration and laser excitation energy on the fluorescence spectra of nicotinamide adenine dinucleotide (NADH) has been investigated. The signature fluorescence peak of NADH was centred about 460 nm. At lower concentration Raman peak centred at 405 nm was also observed. The origin of this peak has been discussed. Detection limit with the proposed set up is found to be 1 ppm.

  15. Plasma temperature clamping in filamentation laser induced breakdown spectroscopy

    SciTech Connect

    Harilal, Sivanandan S.; Yeak, J.; Phillips, Mark C.

    2015-10-19

    Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filamentation channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also partly explains the reason for the occurrence of atomic plume during fs LIBS in air compared to long-pulse ns LIBS.

  16. Laser-induced stress transients: aqueous pores of membranes

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Lee, Shun; Zhang, Hong; McAuliffe, Daniel J., Sr.; Taitelbaum, Jeremy; Doukas, Apostolos G.

    1996-05-01

    Lasers can be used to enhance the delivery of a number of molecules. The model that best fits our data is for the formation of aqueous pores. These pores are present for up to 80 seconds. Our experiments have shown that laser-induced stress transients can be utilized as a vector for intracellular delivery of molecules that may or may not normally cross the cell membrane. These two conditions have been tested with Photofrin and DNA. This technology may have applications in cell and molecular biology, cancer therapy, gene therapy, and others.

  17. Search for Laser-Induced Formation of Antihydrogen Atoms

    SciTech Connect

    Amoretti, M.; Macri, M.; Testera, G.; Variola, A.; Amsler, C.; Pruys, H.; Regenfus, C.; Bonomi, G.; Bowe, P. D.; Ejsing, A. M.; Hangst, J. S.; Madsen, N.; Canali, C.; Carraro, C.; Lagomarsino, V.; Manuzio, G.; Cesar, C. L.; Charlton, M.; Joergensen, L. V.; Mitchard, D.

    2006-11-24

    Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n=11 quantum state by the introduction of light from a CO{sub 2} continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration.

  18. Search for laser-induced formation of antihydrogen atoms.

    PubMed

    Amoretti, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Ejsing, A M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Lodi Rizzini, E; Macrì, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Posada, L G C; Pruys, H; Regenfus, C; Rotondi, A; Telle, H H; Testera, G; Van der Werf, D P; Variola, A; Venturelli, L; Yamazaki, Y; Zurlo, N

    2006-11-24

    Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration.

  19. Laser-induced fluorescence spectroscopy of the secondary cataract

    NASA Astrophysics Data System (ADS)

    Maslov, N. A.; Larionov, P. M.; Rozhin, I. A.; Druzhinin, I. B.; Chernykh, V. V.

    2016-06-01

    Excitation-emission matrices of laser-induced fluorescence of lens capsule epithelium, the lens nucleus, and the lens capsule are investigated. A solid-state laser in combination with an optical parametric generator tunable in the range from 210 to 350 nm was used for excitation of fluorescence. The spectra of fluorescence of all three types of tissues exhibit typical features that are specific to them and drastically differ from one another. This effect can be used for intrasurgical control of presence of residual lens capsule epithelium cells in the capsular bag after surgical treatment of a cataract.

  20. Laser induced fluorescence of biochemical for UV LIDAR application.

    PubMed

    Gupta, L; Sharma, R C; Razdan, A K; Maini, A K

    2014-05-01

    Laser induced fluorescence spectroscopy in the ultraviolet regime has been used for the detection of biochemical through a fiber coupled CCD detector from a distance of 2 m. The effect of concentration and laser excitation energy on the fluorescence spectra of nicotinamide adenine dinucleotide (NADH) has been investigated. The signature fluorescence peak of NADH was centred about 460 nm. At lower concentration Raman peak centred at 405 nm was also observed. The origin of this peak has been discussed. Detection limit with the proposed set up is found to be 1 ppm. PMID:24337816

  1. Laser-induced shock waves effects in materials

    SciTech Connect

    Dingus, R.S.; Shafer, B.P.

    1990-01-01

    A review of the effects of pressure pulses on materials is presented with an orientation toward laser-induced shock wave effects in biological tissue. The behavior is first discussed for small amplitudes, namely sound waves, since many important features in this region are also applicable at large amplitudes. The generation of pressure pulses by lasers is discussed along with amplitudes. The origin and characteristic properties of shock waves are discussed along with the different types of effects they can produce. The hydrodynamic code techniques required for shock wave calculations are discussed along with the necessary empirical data base and methods for generating that data base. 7 refs., 15 figs.

  2. High time resolution laser induced fluorescence in pulsed argon plasma

    SciTech Connect

    Biloiu, Ioana A.; Sun Xuan; Scime, Earl E.

    2006-10-15

    A submillisecond time resolution laser induced fluorescence (LIF) method for obtaining the temporal evolution of the ion velocity distribution function in pulsed argon plasma is presented. A basic LIF system that employs a continuous laser wave pumping and lock-in aided detection of the subsequent fluorescence radiation is modified by addition of a high frequency acousto-optic modulator to provide measurements of the ion flow velocity and ion temperature in a helicon generated pulsed argon plasma with temporal resolutions as high as 30 {mu}s.

  3. Laser-induced micro-jetting from armored droplets

    NASA Astrophysics Data System (ADS)

    Marston, J. O.; Thoroddsen, S. T.

    2015-07-01

    We present findings from an experimental study of laser-induced cavitation within a liquid drop coated with a granular material, commonly referred to as "armored droplets" or "liquid marbles." The cavitation event follows the formation of plasma after a nanosecond laser pulse. Using ultra-high-speed imaging up to 320,610 fps, we investigate the extremely rapid dynamics following the cavitation, which manifests itself in the form of a plethora of micro-jets emanating simultaneously from the spaces between particles on the surface of the drop. These fine jets break up into droplets with a relatively narrow diameter range, on the order of 10 μm.

  4. Progress in fieldable laser-induced breakdown spectroscopy (LIBS)

    NASA Astrophysics Data System (ADS)

    Miziolek, Andrzej W.

    2012-06-01

    In recent years there has been great progress in the Laser Induced Breakdown Spectroscopy (LIBS) technology field. Significant advances have been made both in fundamental and applied research as well as in data processing/chemometrics. Improvements in components, most notably lasers/optics and spectrometers are enabling the development of new devices that are suitable for field use. These new commercial devices recently released to the marketplace, as well as ones currently under development, are bringing the potential of LIBS for CBRNE threat analysis into real-world applications.

  5. The effect of the laser wavelength on collinear double pulse laser induced breakdown spectroscopy (DP-LIBS)

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Lin, Yanqing; Liu, Jing; Fan, Shuang; Xu, Zhuopin; Huang, Qing; Wu, Yuejin

    2016-05-01

    The pulsed lasers at wavelengths of 532 nm and 1064 nm were used as two beams of light for collinear double pulse laser induced breakdown spectroscopy (DP-LIBS). By changing the time sequence of two beams of different lasers, we studied the effect of the interval of two pulses of DP-LIBS on spectral signals compared with single pulsed (SP) LIBS.

  6. Standoff laser-induced thermal emission of explosives

    NASA Astrophysics Data System (ADS)

    Galán-Freyle, Nataly Y.; Pacheco-Londoño, Leonardo C.; Figueroa-Navedo, Amanda; Hernandez-Rivera, Samuel P.

    2013-05-01

    A laser mediated methodology for remote thermal excitation of analytes followed by standoff IR detection is proposed. The goal of this study was to determine the feasibility of using laser induced thermal emission (LITE) from vibrationally excited explosives residues deposited on surfaces to detect explosives remotely. Telescope based FT-IR spectral measurements were carried out to examine substrates containing trace amounts of threat compounds used in explosive devices. The highly energetic materials (HEM) used were PETN, TATP, RDX, TNT, DNT and ammonium nitrate with concentrations from 5 to 200 μg/cm2. Target substrates of various thicknesses were remotely heated using a high power CO2 laser, and their mid-infrared (MIR) thermally stimulated emission spectra were recorded. The telescope was configured from reflective optical elements in order to minimize emission losses in the MIR frequencies and to provide optimum overall performance. Spectral replicas were acquired at a distance of 4 m with an FT-IR interferometer at 4 cm- 1 resolution and 10 scans. Laser power was varied from 4-36 W at radiation exposure times of 10, 20, 30 and 60 s. CO2 laser powers were adjusted to improve the detection and identification of the HEM samples. The advantages of increasing the thermal emission were easily observed in the results. Signal intensities were proportional to the thickness of the coated surface (a function of the surface concentration), as well as the laser power and laser exposure time. For samples of RDX and PETN, varying the power and time of induction of the laser, the calculated low limit of detections were 2 and 1 μg/cm2, respectively.

  7. OCT for glaucoma diagnosis, screening and detection of glaucoma progression.

    PubMed

    Bussel, Igor I; Wollstein, Gadi; Schuman, Joel S

    2014-07-01

    Optical coherence tomography (OCT) is a commonly used imaging modality in the evaluation of glaucomatous damage. The commercially available spectral domain (SD)-OCT offers benefits in glaucoma assessment over the earlier generation of time domain-OCT due to increased axial resolution, faster scanning speeds and has been reported to have improved reproducibility but similar diagnostic accuracy. The capabilities of SD-OCT are rapidly advancing with 3D imaging, reproducible registration, and advanced segmentation algorithms of macular and optic nerve head regions. A review of the evidence to date suggests that retinal nerve fibre layer remains the dominant parameter for glaucoma diagnosis and detection of progression while initial studies of macular and optic nerve head parameters have shown promising results. SD-OCT still currently lacks the diagnostic performance for glaucoma screening. PMID:24357497

  8. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    SciTech Connect

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  9. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Bullock, Anthony Burlingame

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time- delayed, two-color subpicoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence (θdivergence < 5°) shows the ablated plume temperature to be very low at long time delays (T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 μm films show these plumes to be of high neutral atom density (nn of order 10

  10. Neuroinflammation in advanced canine glaucoma

    PubMed Central

    Jiang, Bing; Harper, Matthew M.; Kecova, Helga; Adamus, Grazyna; Kardon, Randy H.; Grozdanic, Sinisa D.

    2010-01-01

    Purpose The pathophysiological events that occur in advanced glaucoma are not well characterized. The principal purpose of this study is to characterize the gene expression changes that occur in advanced glaucoma. Methods Retinal RNA was obtained from canine eyes with advanced glaucoma as well as from healthy eyes. Global gene expression patterns were determined using oligonucleotide microarrays and confirmed by real-time PCR. The presence of tumor necrosis factor (TNF) and its receptors was evaluated by immunolabeling. Finally, we evaluated the presence of serum autoantibodies directed against retinal epitopes using western blot analyses. Results We identified over 500 genes with statistically significant changes in expression level in the glaucomatous retina. Decreased expression levels were detected for large number of functional groups, including synapse and synaptic transmission, cell adhesion, and calcium metabolism. Many of the molecules with decreased expression levels have been previously shown to be components of retinal ganglion cells. Genes with elevated expression in glaucoma are largely associated with inflammation, such as antigen presentation, protein degradation, and innate immunity. In contrast, expression of many other pro-inflammatory genes, such as interferons or interleukins, was not detected at abnormal levels. Conclusions This study characterizes the molecular events that occur in the canine retina with advanced glaucoma. Our data suggest that in the dog this stage of the disease is accompanied by pronounced retinal neuroinflammation. PMID:21042562

  11. Femtosecond Laser-Induced Coulomb Explosion Imaging

    NASA Astrophysics Data System (ADS)

    Karimi, Reza; Liu, Wing-Ki; Sanderson, Joseph

    2016-07-01

    We review recent progress in the field of Coulomb imaging using femtosecond laser pulses of variable length, referred to as Femtosecond Multiple Pulse Length Spectroscopy (FEMPULS). This method introduces a multi-dimensional approach to the study of the molecular dynamics of the multiply ionized triatomic molecules: CO2, OCS, and N2O. We describe the experimental setup used and the approaches needed to optimize the multi-particle detection, coincidence technique. The results show the degree of high resolution imaging which can be achieved with few cycle pulses, and how the onset of charge resonance enhanced ionization (CREI) can be observed as pulse length is increased. By coupling pulse length variation with Dalitz and Newton plotting techniques, stepwise processes can be identified for all three molecules, giving insight into the dynamics, particularly on the 3+ state, which has been revealed as the doorway state to CREI. Finally, in the case of OCS, pulse length variation is shown to have the potential as a control mechanism, as it modulates the ratio of stepwise to concerted processes.

  12. Dielectric breakdown induced by picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

    1976-01-01

    The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

  13. UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry in the diagnostics of alopecia

    NASA Astrophysics Data System (ADS)

    Skomorokha, Diana P.; Pigoreva, Yulia N.; Salmin, Vladimir V.

    2016-04-01

    Development of optical biopsy methods has a great interest for medical diagnostics. In clinical and experimental studies it is very important to analyze blood circulation quickly and accurately, thereby laser Doppler flowmetry (LDF) is widely used. UV laser-induced fluorescence spectroscopy (UV LIFS) is express highly sensitive and widely-spread method with no destructive impact, high excitation selectivity and the possibility to use in highly scattering media. The goal of this work was to assess a correlation of UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry parameters, and a possibility to identify or to differentiate various types of pathological changes in tissues according to their autofluorescence spectra. Three groups of patients with diffuse (symptomatic) alopecia, androgenic alopecia, and focal alopecia have been tested. Each groups consisted of not less than 20 persons. The measurements have been done in the parietal and occipital regions of the sculls. We used the original automated spectrofluorimeter to record autofluorescence spectra, and standard laser Doppler flowmeter BLF-21 (Transonic Systems, Inc., USA) to analyze the basal levels of blood circulation. Our results show that UV LIFS accurately distinguishes the zones with different types of alopecia. We found high correlation of the basal levels of blood circulation and the integrated intensity of autofluorescence in the affected tissue.

  14. Laser-induced microbubble poration of localized single cells.

    PubMed

    Fan, Qihui; Hu, Wenqi; Ohta, Aaron T

    2014-05-01

    Laser-induced microbubbles were used to porate the cell membranes of localized single NIH/3T3 fibroblasts. Microsecond laser pulses were focused on an optically absorbent substrate, creating a vapour microbubble that oscillated in size at the laser focal point in a fluidic chamber. The shear stress accompanying the bubble size oscillation was able to porate nearby cells. Cell poration was demonstrated with the delivery of FITC-dextran dye with various molecular weights. Under optimal poration conditions, the cell poration efficiency was up to 95.2 ± 4.8%, while maintaining 97.6 ± 2.4% cell viability. The poration system is able to target a single cell without disturbing surrounding cells. PMID:24632785

  15. Trigonometric pulse envelopes for laser-induced quantum dynamics

    NASA Astrophysics Data System (ADS)

    Barth, I.; Lasser, C.

    2009-12-01

    We relate powers of trigonometric functions to Gaussians by proving that properly truncated cosn functions converge to a Gaussian as n tends to infinity. For an application, we analyse the laser-induced population transfer |X1Σ+rang → |A1Πxrang in a two-level model system of aluminium monochloride (AlCl) with fixed nuclei. We apply linearly x-polarized ultraviolet laser pulses with a trigonometric envelope function, whose square has full width at half-maximum of 2.5 fs and 5.0 fs. Studying population dynamics and optimized laser parameters, we find that the optimal field amplitude for trigonometric pulses with n = 20 and n = 1000 has a relative difference of 1%, which is below experimental resolution.

  16. Laser-induced stress transients: applications for molecular delivery

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Lee, Shun; Zhang, Hong; McAuliffe, Daniel J.; Douki, Tina; Doukas, Apostolos G.

    1995-05-01

    Lasers can be used to enhance the delivery of a number of molecules. Other investigators have demonstrated local release of molecules from liposomes following laser irradiation, microbeam disruption of the cell membrane to increase cell transport, microbeam ablation of the zona pellucida surrounding the ovum to increase the chances of fertilization, and increased transcutaneous transport following ablation of the stratum corneum. Our experiments have shown that laser-induced stress transients can be utilized as a vector for intracellular delivery of molecules that may or may not normally cross the cell membrane. These two conditions have been tested with Photofrin and DNA. This technology may have applications in cell and molecular biology, cancer therapy, gene therapy, and others.

  17. Laser-induced modification of transparent crystals and glasses

    SciTech Connect

    Bulgakova, N M; Stoian, Razvan; Rosenfeld, A

    2010-12-29

    We analyse the processes taking place in transparent crystals and glasses irradiated by ultrashort laser pulses in the regimes typical of various applications in optoelectronics and photonics. We consider some phenomena, which have been previously described by the authors within the different model representations: charging of the dielectric surface due to electron photoemission resulting in a Coulomb explosion; crater shaping by using an adaptive control of the laser pulse shape; optimisation of the waveguide writing in materials strongly resistant to laser-induced compaction under ordinary irradiation conditions. The developed models and analysis of the processes relying on these models include the elements of the solid-state physics, plasma physics, thermodynamics, theory of elasticity and plasticity. Some important experimental observations which require explanations and adequate description are summarised. (photonics and nanotechnology)

  18. Containerless study of metal evaporation by laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, Robert A.; Nordine, Paul C.

    1987-01-01

    Laser induced fluorescence (LIF) detection of atomic vapors was used to study evaporation from electromagnetically levitated and CW CO2 laser-heated molybdenum spheres and resistively-heated tungsten filaments. Electromagnetic (EM) levitation in combination with laser heating of tungsten, zirconium, and aluminum specimens was also investigated. LIF intensity vs temperature data were obtained for molybdenum atoms and six electronic states of atomic tungsten, at temperatures up to the melting point of each metal. The detected fraction of the emitted radiation was reduced by self-absorption effects at the higher experimental temperatures. Vaporization enthalpies derived from data for which less than half the LIF intensity was self-absorbed were -636 + or - 24 kJ/g-mol for Mo and 831 + or - 32 kJ/g-mol for W. Space-based applications of EM levitation in combination with radiative heating are discussed.

  19. Laser-induced jet formation in liquid films

    NASA Astrophysics Data System (ADS)

    Brasz, Frederik; Arnold, Craig

    2014-11-01

    The absorption of a focused laser pulse in a liquid film generates a cavitation bubble on which a narrow jet can form. This is the basis of laser-induced forward transfer (LIFT), a versatile printing technique that offers an alternative to inkjet printing. We study the influence of the fluid properties and laser pulse energy on jet formation using numerical simulations and time-resolved imaging. At low energies, surface tension causes the jet to retract without transferring a drop, and at high energies, the bubble breaks up into a splashing spray. We explore the parameter space of Weber number, Ohnesorge number, and ratio of film thickness to maximum bubble radius, revealing regions where uniform drops are transferred.

  20. Microfabrication of Fresnel zone plates by laser induced solid ablation

    NASA Astrophysics Data System (ADS)

    Rodrigues, Vanessa R. M.; Thomas, John; Santhosh, Chidangil; Ramachandran, Hema; Mathur, Deepak

    2016-07-01

    A novel and simple single-step method of inscribing optical elements on metal-coated transparent substrates is demonstrated. Laser induced solid ablation (LISA) demands very low laser energies (nJ), as can be amply provided by a femtosecond laser oscillator. Here, LISA is used to write Fresnel zone plates on indium and tungsten coated glass. With up to 100 zones, remarkable agreement is obtained between measured and expected values of the focal length. LISA has enabled attainment of focal spot sizes that are 38% smaller than what would be obtained using conventional lenses of the same numerical aperture. The simplicity with which a high degree of automation can readily be achieved using LISA makes this cost-effective method amenable to a wide variety of applications related to microfabrication of optical elements.

  1. Laser-induced breakdown spectroscopy expands into industrial applications

    NASA Astrophysics Data System (ADS)

    Noll, Reinhard; Fricke-Begemann, Cord; Brunk, Markus; Connemann, Sven; Meinhardt, Christoph; Scharun, Michael; Sturm, Volker; Makowe, Joachim; Gehlen, Christoph

    This paper presents R&D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal structure of LIBS machines embedded for inline process monitoring will be presented. A systematic requirement analysis for LIBS systems following Ishikawa's scheme was worked out. Stability issues are studied for laser sources and Paschen-Runge spectrometers as key components for industrial LIBS systems. Examples of industrial applications range from handheld LIBS systems using a fiber laser source, via a set of LIBS machines for inline process control tasks, such as scrap analysis, coal analysis, liquid slag analysis and finally monitoring of drill dust.

  2. Determination of phosphorus in steel by the combined technique of laser induced breakdown spectrometry with laser induced fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Kondo, Hiroyuki; Hamada, Naoya; Wagatsuma, Kazuaki

    2009-09-01

    Laser induced breakdown spectrometry (LIBS) combined with laser induced fluorescence spectrometry (LIFS) has been applied for detection of trace-level phosphorus in steel. The plasma induced by irradiation of Nd:YAG laser pulse for ablation was illuminated by the 3rd harmonic of Ti:Sapphire laser tuned to one of the resonant lines for phosphorus in the wavelength region of 253-256 nm. An excitation line for phosphorus was selected to give the highest signal-to-noise ratio. Fluorescence signals, P213.62 and P214.91 nm, were observed with high selectivity at the contents as low as several tens µg g - 1 . Fluorescence intensities were in a good linear correlation with the contents. Fluorescence intensity ratio of a collisionally assisted line (213.62 nm) to a direct transition line (214.91 nm) was discussed in terms of the analytical conditions and experimental results were compared with a calculation based on rate equations. Since the fluorescence signal light in the wavelength range longer than 200 nm can be transmitted relatively easily, even through fiber optics of moderate length, LIBS/LIFS would be a versatile technique in on-site applications for the monitoring of phosphorus contents in steel.

  3. Nanosecond laser-induced phase transitions in pulsed laser deposition-deposited GeTe films

    SciTech Connect

    Sun, Xinxing Thelander, Erik; Lorenz, Pierre; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

    2014-10-07

    Phase transformations between amorphous and crystalline states induced by irradiation of pulsed laser deposition grown GeTe thin films with nanosecond laser pulses at 248 nm and pulse duration of 20 ns are studied. Structural and optical properties of the Ge-Te phase-change films were studied by X-ray diffraction and optical reflectivity measurements as a function of the number of laser pulses between 0 and 30 pulses and of the laser fluence up to 195 mJ/cm². A reversible phase transition by using pulse numbers ≥ 5 at a fluence above the threshold fluence between 11 and 14 mJ/cm² for crystallization and single pulses at a fluence between 162 and 182 mJ/cm² for amorphization could be proved. For laser fluences from 36 up to 130 mJ/cm², a high optical contrast of 14.7% between the amorphous and crystalline state is measured. A simple model is used that allows the discussion on the distribution of temperature in dependency on the laser fluence.

  4. Characterization of hard coatings produced by laser cladding using laser-induced breakdown spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Varela, J. A.; Amado, J. M.; Tobar, M. J.; Mateo, M. P.; Yañez, A.; Nicolas, G.

    2015-05-01

    Protective coatings with a high abrasive wear resistance can be obtained from powders by laser cladding technique, in order to extend the service life of some industrial components. In this work, laser clad layers of self-fluxing NiCrBSi alloy powder mixed with WC powder have been produced on stainless steel substrates of austenitic type (AISI 304) in a first step and then chemically characterized by laser-induced breakdown spectroscopy (LIBS) technique. With the suitable laser processing parameters (mainly output power, beam scan speed and flow rate) and powders mixture proportions between WC ceramics and NiCrBSi alloys, dense pore free layers have been obtained on single tracks and on large areas with overlapped tracks. The results achieved by LIBS technique and applied for the first time to the analysis of laser clads provided the chemical composition of the tungsten carbides in metal alloy matrix. Different measurement modes (multiple point analyses, depth profiles and chemical maps) have been employed, demonstrating the usefulness of LIBS technique for the characterization of laser clads based on hardfacing alloys. The behavior of hardness can be explained by LIBS maps which evidenced the partial dilution of some WC spheres in the coating.

  5. Effects of laser parameters on propagation characteristics of laser-induced stress wave for gene transfer

    NASA Astrophysics Data System (ADS)

    Ando, Takahiro; Sato, Shunichi; Terakawa, Mitsuhiro; Ashida, Hiroshi; Obara, Minoru

    2010-02-01

    Laser-based gene delivery is attractive as a new method for topical gene therapy because of the high spatial controllability of laser energy. Previously, we demonstrated that an exogenous gene can be transferred to cells both in vitro and in vivo by applying nanosecond pulsed laser-induced stress waves (LISWs) or photomechanical waves (PMWs). In this study, we investigated effects of laser parameters on the propagation characteristics of LISWs in soft tissue phantoms and depth-dependent properties of gene transfection. Temporal pressure profiles of LISWs were measured with a hydrophone, showing that with a larger laser spot diameter, LISWs can be propagated more efficiently in phantoms with keeping flat wavefront. Phantoms with various thicknesses were placed on the rat dorsal skin that had been injected with plasmid DNA coding for reporter gene, and LISWs were applied from the top of the phantom. Efficient gene expression was observed in the rat skin that had interacted with LISWs propagating through a 15-mm-thick phantom. These results would be useful to determine appropriate laser parameters for gene delivery to deep-located tissue by transcutaneous application of LISWs.

  6. Enhanced efficiency of laser shock cleaning process by geometrical confinement of laser-induced plasma

    SciTech Connect

    Jang, Deoksuk; Oh, Joon Ho; Kim, Dongsik; Lee, Jong-Myoung

    2009-07-01

    Surface cleaning based on the laser-induced breakdown of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. Accordingly, several studies were performed to expand the cleaning capability of the process. In this work, the cleaning process using laser-induced plasma (LIP) under geometrical confinement is analyzed both theoretically and experimentally. Two-dimensional numerical analysis is conducted to examine the behavior of the LIP shock wave under geometrical confinement for several geometries. As a result of the analysis, we propose a simple and practical method to amplify the intensity of laser-induced shock. In the proposed method, a flat quartz plate placed close to the focal point of the laser pulse confines the expansion of the LIP, allowing the plasma to expand only in one direction. As a consequence of the plasma confinement, the intensity of the shock wave produced is increased significantly. Experiments demonstrate that the enhanced shock wave can remove smaller particles from the surface better than the existing process.

  7. Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma: A Review of the Literature with Updates on Surgical Management

    PubMed Central

    Plateroti, Pasquale; Plateroti, Andrea Maria; Abdolrahimzadeh, Solmaz; Scuderi, Gianluca

    2015-01-01

    Pseudoexfoliation syndrome (PES) is a systemic disorder caused by progressive accumulation of extracellular material over various tissues. PES usually determines increased intraocular pressure, changes in the anatomical aspects of the optic nerve, and visual field alterations leading to the diagnosis of pseudoexfoliation glaucoma (PEG). Use of topical medical treatment usually leads to poor results in terms of long-term follow-up but many surgical techniques, such as Argon Laser or Selective Laser Trabeculoplasty, have been proposed for the management of PEG affected patients. The present paper is a review on the pseudoexfoliation syndrome and pseudoexfoliation glaucoma with an update on surgical management. PMID:26605078

  8. Laser-induced autofluorescence for medical diagnosis.

    PubMed

    Koenig, K; Schneckenburger, H

    1994-03-01

    The naturally occurring autofluorescence of cells and tissues is based on biomolecules containing intrinsic fluorophores, such as porphyrins, the amino acids tryptophan and tyrosine, and the coenzymes NADH, NADPH, and flavins. Coenzymes fluoresce in the blue/green spectral region (fluorecence lifetimes: 0.5-6 ns) and are highly sensitive indicators of metabolic function. Steadystate and time-resolved blue-green autofluorescence is, therefore, an appropriate measure of the function of the respiratory chain as well as of cellular and tissue damage. Autofluorescence in the yellow/red spectral region is based mainly on endogenous porphyrins and metalloporphyrins, such as coproporphyrin, protoporphyrin (fluorescence lifetime of porphyrin monomers: >10 ns), and Zn-protoporphyrin (2 ns). Various pathological microorganisms such asPropionibacterium acnes, Pseudomonas aeruginosa, Actinomyces odontolyticus, Bacteroides intermedius, andSaccharomyces cerevisiae are able to synthesize large amounts of these fluorophores and can therefore be located. This permits fluorescence-based detection of a variety of diseases, including early-stage dental caries, dental plaque, acne vulgaris, otitis externa, and squamous cell carcinoma. The sensitivity of noninvasive autofluorescence diagnostics can be enhanced by time-gated fluorescence measurements using an appropriate time delay between ultrashort laser excitation and detection. For example, videocameras with ultrafast shutters, in the nanosecond region, can be used to create "caries images" of the teeth. Alternatively, autofluorescence can be enhanced by stimulating protoporphyrin biosynthesis with the exogenously administered porphyrin precursor 5-aminolevulinic acid (ALA). The fluorophore protoporphyrin IX (PP IX) is photolabile and photodynamically active. Irradiation of PP IX-containing tissue results in cytotoxic reactions which correlate with modifications in fluorescence due to photobleaching and singlet oxygen

  9. Pediatric genetic diseases causing glaucoma.

    PubMed

    Ichhpujani, Parul; Singh, Rohan B

    2014-12-01

    Glaucomatous optic neuropathy may be considered as an endpoint of multiple systemic factors. Genetic conditions commonly causing glaucoma in children and adolescents include Axenfeld-Reiger syndrome, aniridia, Marfan syndrome, Weill-Marchessani syndrome, Sturge-Weber syndrome, Rubinstein-Taybi syndrome, nevus of Ota, congenital rubella and neurofibromatosis type 1. In the recent years, with the advancements in genetic research our understanding of the fundamental causes of glaucoma associated with inherited disorders has improved. In addition to intraocular pressure reduction, it is important for the clinician to be familiar with the multiple systemic associations with glaucoma, to re-evaluate treatment frequently, and to target the underlying disease process, if present. PMID:27625878

  10. [Non-penetrating glaucoma surgery].

    PubMed

    Klink, T; Matlach, J; Grehn, F

    2012-08-01

    Patients at high risk of developing complications (e.g. high myopia, aphakia, advanced visual field defects) benefit from non-penetrating glaucoma surgery (NPGS). Neovascular glaucoma, traumatic glaucoma or patients with a narrow angle (a scleral spur must at least be visible) are not suitable for NPGS. The aim of deep sclerectomy (DS) is mainly external subconjunctival drainage. Modified with mitomycin C and intrascleral implants, intraocular pressure (IOP) and success of DS are comparable to trabeculectomy. Viscocanalostomy and the further development to canaloplasty aim for blebless IOP control. Viscocanalostomy has an extremely low complication profile but only a slight reduction in IOP. Canaloplasty creates much more favourable results. Combined with phacoemulsification canaloplasty appears to lower IOP comparable to phacotrabeculectomy and demonstrates a more sustainable success compared to canaloplasty alone.

  11. Pediatric genetic diseases causing glaucoma

    PubMed Central

    Ichhpujani, Parul; Singh, Rohan B.

    2014-01-01

    Glaucomatous optic neuropathy may be considered as an endpoint of multiple systemic factors. Genetic conditions commonly causing glaucoma in children and adolescents include Axenfeld-Reiger syndrome, aniridia, Marfan syndrome, Weill-Marchessani syndrome, Sturge-Weber syndrome, Rubinstein-Taybi syndrome, nevus of Ota, congenital rubella and neurofibromatosis type 1. In the recent years, with the advancements in genetic research our understanding of the fundamental causes of glaucoma associated with inherited disorders has improved. In addition to intraocular pressure reduction, it is important for the clinician to be familiar with the multiple systemic associations with glaucoma, to re-evaluate treatment frequently, and to target the underlying disease process, if present. PMID:27625878

  12. Laser ablation of powdered samples and analysis by means of laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ctvrtnickova, T.; Cabalin, L.; Laserna, J.; Kanicky, V.; Nicolas, G.

    2009-03-01

    The presented work proves the capacities of laser-induced breakdown spectroscopy (LIBS) as a fast, universal, and versatile technique for analysis of complex materials as ceramics. This paper reports on the analysis of ceramic raw materials (brick clays and kaolin) submitted to laser ablation in the form of pressed pellets. Spectrographic study was provided by standard single-pulse LIBS technique and orthogonal reheating double-pulse LIBS. It was found that both methods are comparable in terms of analytical performance, if adequate experimental parameters and signal detection systems are used.

  13. Common-Path Heterodyne Laser-Induced Thermal Acoustics for Seedless Laser Velocimetry

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, G. C.; Balla, R. Jeffrey; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    We demonstrate the use of a novel technique for the detection of heterodyne laser-induced thermal acoustics signals, which allows the construction of a highly stable seedless laser velocimeter. A common-path configuration is combined with quadrature detection to provide flow direction, greatly improve robustness to misalignment and vibration, and give reliable velocity measurement at low flow velocities. Comparison with Pitot tube measurements in the freestream of a wind tunnel shows root-mean-square errors of 0.67 m/s over the velocity range 0.55 m/s.

  14. Laser-based diagnostics for coal gasification instrumentation. [Coherent anti-Stokes Raman spectroscopy (CARS), laser induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF)

    SciTech Connect

    Taylor, D.J.; Loree, T.R.; Hartford, A. Jr.; Tiee, J.J.

    1984-01-01

    In this program the investigators have investigated the suitability of a number of optical diagnostic techniques for nonintrusive real-time measurements of species concentrations and temperatures of coal gasification streams. They have identified and evaluated several promising techniques including coherent Raman spectroscopy, laser-induced breakdown spectroscopy, and laser-induced fluorescence. They emphasize that these are complementary, rather than competing, diagnostic technologies, as each can provide a different class of data for gasifier operation. The results of their gasifier field tests and supporting laboratory work on these diagnostic techniques have been summarized and recommendations for continued work on optical diagnostics for coal gasification streams are presented. 12 references, 17 figures.

  15. Laser-induced nuclear magnetic resonance splitting in hydrocarbons.

    PubMed

    Ikäläinen, Suvi; Lantto, Perttu; Manninen, Pekka; Vaara, Juha

    2008-09-28

    Irradiation of matter with circularly polarized light (CPL) shifts all nuclear magnetic resonance (NMR) lines. The phenomenon arises from the second-order interaction of the electron cloud with the optical field, combined with the orbital hyperfine interaction. The shift occurs in opposite directions for right and left CPL, and rapid switching between them will split the resonance lines into two. We present ab initio and density functional theory predictions of laser-induced NMR splittings for hydrocarbon systems with different sizes: ethene, benzene, coronene, fullerene, and circumcoronene. Due to the computationally challenging nature of the effect, traditional basis sets could not be used for the larger systems. A novel method for generating basis sets, mathematical completeness optimization, was employed. As expected, the magnitude of the spectral splitting increases with the laser beam frequency and polarizability of the system. Massive amplification of the effect is also observed close to the optical excitation energies. A much larger laser-induced splitting is found for the largest of the present molecules than for the previously investigated noble gas atoms or small molecules. The laser intensity required for experimental detection of the effect is discussed.

  16. Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

    NASA Astrophysics Data System (ADS)

    Viljanen, Jan; Sun, Zhiwei; Alwahabi, Zeyad T.

    2016-04-01

    Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45 GHz and of 1 millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~ 100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1 ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

  17. Laser-induced nucleation of carbon dioxide bubbles.

    PubMed

    Ward, Martin R; Jamieson, William J; Leckey, Claire A; Alexander, Andrew J

    2015-04-14

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm(-2)) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm(-2)) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm(-2)). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  18. Laser-induced breakdown spectroscopy of tantalum plasma

    SciTech Connect

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq

    2013-07-15

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  19. A retrospective survey of childhood glaucoma prevalence according to Childhood Glaucoma Research Network classification

    PubMed Central

    Hoguet, Ambika; Grajewski, Alana; Hodapp, Elizabeth; Chang, Ta Chen Peter

    2016-01-01

    Purpose: To evaluate the Childhood Glaucoma Research Network (CGRN) classification system and describe the prevalence of each subtype according to this classification. Materials and Methods: Retrospectively, the medical records of 205 consecutive childhood glaucoma and glaucoma suspect patients at an urban tertiary care center were reviewed. The initial diagnosis and new diagnosis according to CGRN classification were recorded. Results: All patients fit one of the seven categories of the new classification. Seventy-one percent of diagnoses were changed upon reclassification. Twenty-three percent of patients had primary glaucoma (juvenile open-angle glaucoma and primary congenital glaucoma [PCG]); 36% had secondary glaucoma (glaucoma associated with nonacquired ocular anomalies; glaucoma associated with nonacquired systemic disease or syndrome; glaucoma associated with acquired condition; and glaucoma following cataract surgery); and 39% were glaucoma suspect. Of the patients diagnosed with glaucoma, PCG was the most common diagnosis, seen in 32% of patients. Conclusion: The CGRN classification provides a useful method of classifying childhood glaucoma. PMID:27050345

  20. Liquid explosions induced by X-ray laser pulses

    NASA Astrophysics Data System (ADS)

    Stan, Claudiu; Laksmono, Hartawan; Sierra, Raymond; McQueen, Trevor; Milathianaki, Despina; Koglin, Jason; Lane, Thomas; Messerschmidt, Marc; Williams, Garth; Hayes, Matt; Guillet, Serge; Botha, Sabine; Nass, Karol; Schlichting, Ilme; Shoeman, Robert; Stone, Howard; Boutet, Sébastien

    2015-11-01

    Sudden generation and release of enough energy to vaporize matter are encountered in systems that range from supernovae explosions and asteroid impacts to applications in fusion energy generation, materials processing, and laser surgery. Understanding these strong explosions is important to both fundamental science and technical applications. We studied a new type of microexplosion, induced by absorption of X-ray pulses from a free-electron laser in micron-sized drops and jets of water. These explosions are related to, but different from, those observed in experiments performed with optical lasers. Unlike explosions caused by optical lasers, X-ray laser explosions produce symmetric expansion patterns that are simpler to rationalize. The release of energy initially concentrated in a small region inside drops and jets leads to ballistic vapor flow and inertial liquid flow. The kinematics of these flows indicates that the conversion of the energy deposited by X-rays into flow has a scaling that is similar to the one encountered in shock waves.

  1. Laser-Induced Shocks in Strongly Coupled Aluminum Plasmas

    NASA Astrophysics Data System (ADS)

    Tierney, T.; Benage, J.; Evans, S.; Glocer, A.; Kyrala, G.; Montoya, R.; Munson, C.; Roberts, J.; Skidmore, B.; Taylor, A.; Wood, B.; Workman, J.; Wysocki, F.

    2001-10-01

    Inverse bremsstrahlung is a dominant absorption mechanism at high densities and low temperatures, such as in strongly coupled plasmas. We electrically produce a 0.1 g/cm^3, 1 eV SCP target which is struck by a 2-3 J, 0.8 ns frequency-doubled Nd:Yag laser pulse. Under these conditions, the laser pulse couples into the plasma where the electron plasma frequency equals the laser frequency. For a wavelength of 532 nm, this happens at a critical density of ne = 4x10^21 cm-3. The rapid deposition of energy heats and compresses the plasma to shock conditions. The surface temperature of the plasma is measured using four filtered PMTs with the assumption of blackbody emission with constant emissivity. Pre-shocked and shocked density measurements are simultaneously made using a laser-produced Ti K-shell (4.75 keV) x-ray shadowgraph. We present the experiment design and results of a laser-induced shock in a strongly coupled plasma.

  2. Applications of laser-induced gratings to spectroscopy and dynamics

    SciTech Connect

    Rohlfing, E.A.

    1993-12-01

    This program has traditionally emphasized two principal areas of research. The first is the spectroscopic characterization of large-amplitude motion on the ground-state potential surface of small, transient molecules. The second is the reactivity of carbonaceous clusters and its relevance to soot and fullerene formation in combustion. Motivated initially by the desire to find improved methods of obtaining stimulated emission pumping (SEP) spectra of transients, most of our recent work has centered on the use of laser-induced gratings or resonant four-wave mixing in free-jet expansions. These techniques show great promise for several chemical applications, including molecular spectroscopy and photodissociation dynamics. The author describes recent applications of two-color laser-induced grating spectroscopy (LIGS) to obtain background-free SEP spectra of transients and double resonance spectra of nonfluorescing species, and the use of photofragment transient gratings to probe photodissociation dynamics.

  3. Laser-induced photo-thermal magnetic imaging

    NASA Astrophysics Data System (ADS)

    Thayer, David A.; Lin, Yuting; Luk, Alex; Gulsen, Gultekin

    2012-08-01

    Due to the strong scattering nature of biological tissue, optical imaging beyond the diffusion limit suffers from low spatial resolution. In this letter, we present an imaging technique, laser-induced photo-thermal magnetic imaging (PMI), which uses laser illumination to induce temperature increase in a medium and magnetic resonance imaging to map the spatially varying temperature, which is proportional to absorbed energy. This technique can provide high-resolution images of optical absorption and can potentially be used for small animal as well as breast cancer and lymph node imaging. First, we describe the theory of PMI, including the modeling of light propagation and heat transfer in tissue. We also present experimental data with corresponding predictions from theoretical models, which show excellent agreement.

  4. Nanosecond-gated laser induced breakdown spectroscopy in hydrocarbon mixtures

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazunobu; Bak, Moon Soo; Tanaka, Hiroki; Do, Hyungrok

    2015-09-01

    Nanosecond-gated laser induced breakdown spectroscopy have been carried out in four different hydrocarbon gas mixtures (CH4/CO2/O2/N2, C2H4/O2/N2, C3H8/CO2/O2/N2 and C4H10/CO2/O2/N2) to investigate the effect of gas species on the laser induced breakdown kinetics and resulting the plasma emission. For this purpose, each mixture that consists of different species has the same atom composition. It is found that the temporal emission spectra and the decay rates of atomic line-intensities are almost identical for the breakdowns in the four different mixtures. This finding may indicate that the breakdown plasmas of these mixtures reach a similar thermodynamic and physiochemical state after its formation, resulting in a similar trend of quenching of excited species.

  5. FEM simulation of residual stresses induced by laser Peening

    NASA Astrophysics Data System (ADS)

    Peyre, P.; Sollier, A.; Chaieb, I.; Berthe, L.; Bartnicki, E.; Braham, C.; Fabbro, R.

    2003-08-01

    Benefits from laser Peening have been demonstrated several times in fields like fatigue, wear or stress corrosion cracking. However, in spite of recent work on the calculation of residual stresses, very few authors have considered a finite element method (FEM) approach to predict laser-induced mechanical effect. This comes mainly from the high strain rates involved during LP (10^6 s^{-1}), that necessitate the precise determination of dynamic properties, and also from the possible combination of thermal and mechanical loadings in the case of LP without protective coatings. In this paper, we aim at presenting a global approach of the problem, starting from the determination of loading conditions and dynamic yield strengths, to finish with FEM calculation of residual stress fields induced on a 12% Cr martensitic stainless steel and a 7075 aluminium alloy.

  6. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R.; Di Benedetto, J.

    1994-06-01

    The ability to induce, detect and discriminate fluorescence of uranium oxides makes available new capabilities for screening the surface of large complex facilities for uranium. This paper will present the results of field tests evaluate laser-induced fluorescence (LIF) as a contamination screening tool and report on the progress to produce a field portable instrument for uranium surveys on exposed surfaces. The principal effect is to illuminate the surface of an object or an area with a remotely-located light source, and to evaluate the re-radiated emission energy. A gated intensified CCD camera was used with ultraviolet (UV) laser excitation to discriminate the phosphorescent (persistent) green uranium emission from the prompt background fluorescence which results from excitation of plants, concrete, soils, and other background materials.

  7. Blood groups as genetic markers in glaucoma.

    PubMed

    Brooks, A M; Gillies, W E

    1988-04-01

    A series of 474 mixed cases of glaucoma was assessed to determine whether there were any genetic differences between different types of glaucoma. A careful distinction was made between chronic open angle glaucoma (COAG), acute and chronic angle closure glaucoma, ocular hypertension, low tension glaucoma, patients with large cup disc ratios, and various types of secondary glaucoma including pseudoexfoliation of the lens capsule, uveitic and traumatic glaucoma. Using ABO blood groups, Rhesus groups, ABH secretion or non-secretion, and phenylthiourea tasting we identified certain differences. The differences from normal were significant decrease in Rh-negative patients in chronic closed angle glaucoma (p less than 0.05), a decrease in ABH secretors in ocular hypertension (p less than 0.01), and fewer HB secretors in patients with COAG (p less than 0.02). There was a significant decrease in AH secretors and increase in HB secretors in both pseudoexfoliation with raised intraocular pressure compared with COAG (p less than 0.01) and in secondary glaucomas as a group compared with COAG (p less than 0.01). Tasters of phenylthiourea were more common in traumatic and uveitic glaucoma than in normal controls (p less than 0.05). These results suggest that secondary glaucoma develops in different subjects from COAG, while patients who develop a rise in intraocular pressure proceed to cupping and field loss if they have a certain genetic constitution. The groups of patients are too small for the differences to be of great prognostic value.

  8. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, S.M.

    1983-10-31

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  9. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, Steven M.

    1988-01-01

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  10. Laser-induced transient grating setup with continuously tunable period

    SciTech Connect

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.

    2015-12-15

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  11. Dynamics of femtosecond laser induced voidlike structures in fused silica

    SciTech Connect

    Mermillod-Blondin, A.; Bonse, J.; Rosenfeld, A.; Hertel, I. V.; Meshcheryakov, Yu. P.; Bulgakova, N. M.; Audouard, E.; Stoian, R.

    2009-01-26

    Focused ultrafast laser irradiation of fused silica usually induces a spatially modulated refractive index variation in the bulk material. Strong energy concentration leads to the localized formation of a lower-density cavitylike depressed structure surrounded by compacted matter. We report on applying time-resolved phase contrast microscopy to investigate the timescale of the void formation. We indicate a temporal behavior consistent with shock wave generation and subsequent rarefaction.

  12. Laser-induced breakdown spectroscopy for specimen analysis

    DOEpatents

    Kumar, Akshaya; Yu-Yueh, Fang; Burgess, Shane C.; Singh, Jagdish P.

    2006-08-15

    The present invention is directed to an apparatus, a system and a method for detecting the presence or absence of trace elements in a biological sample using Laser-Induced Breakdown Spectroscopy. The trace elements are used to develop a signature profile which is analyzed directly or compared with the known profile of a standard. In one aspect of the invention, the apparatus, system and method are used to detect malignant cancer cells in vivo.

  13. High repetition rate laser induced fluorescence applied to Surfatron Induced Plasmas

    NASA Astrophysics Data System (ADS)

    van der Mullen, J. J. A. M.; Palomares, J. M.; Carbone, E. A. D.; Graef, W.; Hübner, S.

    2012-05-01

    The reaction kinetics in the excitation space of Ar and the conversion space of Ar-molecule mixtures are explored using a combination of high rep-rate YAG-Dye laser systems with a well defined and easily controllable Surfatron Induced Plasma set-up. Applying the method of Saturation Time Resolved Laser Induced Fluorescence (SaTiRe-LIF), we could trace excitation and conversion channels and determine rates of electron and heavy particle excitation kinetics. The time resolved density disturbances observed in the Ar excitation space, which are initiated by the laser, reveal the excitation channels and corresponding rates; responses of the molecular radiation in Ar-molecule mixtures corresponds to the presence of conversion processes induced by heavy particle excitation kinetics.

  14. Simulation and characterization of laser induced deformation processes

    NASA Astrophysics Data System (ADS)

    Fan, Yajun

    2006-04-01

    Laser induced deformation processes include laser forming (LF) and laser shock processing. LF is a recently developed and highly flexible thermal forming technique, and laser shock processing is an innovative mechanical process in which shock waves up to 10GPa are generated by a confined laser ablation process. The generated high pressure imparts beneficial residual stress into the surface layer of metal parts as well as shapes thin metal parts. In laser forming, it has been known that microstructural evolution has an important effect on the deformation process, and that the typical thermal cycles in laser forming are much steeper than those in other thermal mechanical processes like welding and hot rolling. In this study, microstructural evolution in laser forming has been investigated, and a thermal-microstructural-mechanical model is developed to predict microstructural changes (phase transformations and recrystallization) and their effects on flow behavior and deformation. Grain structure and phase transformation in heat affected zone (HAZ) is experimentally characterized, and measurement of bending curvature also helps to validate the proposed model. Based on the similar methodology, two different materials have been studied: AISI 1010 low carbon steel and Ti-6Al-4V alloy. In the case of Ti-6A1-4V alloy, the initial phase ratio of Ti-alpha and Ti-beta need to be measured by X-ray diffraction. In laser shock processing, under shock loading solid material behavior is fluidlike and shock-solid interactions play a key role in determining the induced residual stress distributions and the final deformed shape. In this work shock-solid interactions under high pressure and thus high strain rate in laser shock processing are studied and simulated based on conservation's law, equation of state and elastoplasticity of material. A series of carefully controlled experiments, including spatially resolved residual stress measurement by synchrotron X-ray diffraction and

  15. Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions

    NASA Astrophysics Data System (ADS)

    Yan, Zijie

    2011-12-01

    Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been

  16. Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

  17. Laser filamentation induced bubbles and their motion in water.

    PubMed

    Liu, Fengjiang; Yuan, Shuai; Zuo, Zhong; Li, Wenxue; Ding, Liang'en; Zeng, Heping

    2016-06-13

    We demonstrate femtosecond filamentation induced convection in water by using a microscope directly observing the dynamic processes of the generated bubbles on a macroscopic time scale. The bubbles are driven by the filament in water and do directional movements. The angles between the bubbles' moving directions and the laser propagation direction varied at different positions along the filament, exhibiting a fusiform distribution. It indicates a fluid dynamic phenomenon depending on the local filament intensity, and reveals the convection processes induced by filamentation in water indirectly. PMID:27410343

  18. Laser-induced fluorescence detection of hot molecular oxygen in flames using an alexandrite laser.

    PubMed

    Kiefer, Johannes; Zhou, Bo; Zetterberg, Johan; Li, Zhongshan; Alden, Marcus

    2014-01-01

    The use of an alexandrite laser for laser-induced fluorescence (LIF) spectroscopy and imaging of molecular oxygen in thermally excited vibrational states is demonstrated. The laser radiation after the third harmonic generation was used to excite the B-X (0-7) band at 257 nm in the Schumann-Runge system of oxygen. LIF emission was detected between 270 and 380 nm, revealing distinct bands of the transitions from B(0) to highly excited vibrational states in the electronic ground state, X (v > 7). At higher spectral resolution, these bands reveal the common P- and R-branch line splitting. Eventually, the proposed LIF approach was used for single-shot imaging of the two-dimensional distribution of hot oxygen molecules in flames.

  19. Laser-induced breakdown spectroscopy with laser irradiation on mid-infrared hydride stretch transitions: polystyrene

    NASA Astrophysics Data System (ADS)

    Khachatrian, A.; Dagdigian, P. J.

    2009-09-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of a polymer (polystyrene) with laser irradiation in the mid-infrared (mid-IR) spectral region is presented. A particular goal of this study is to determine whether the LIBS signals are enhanced when the laser wavelength is tuned to that of a vibrational transition of the polymer. Significant enhancements were indeed observed upon irradiation on the C-H stretch fundamental vibrational transitions. In addition, mode-specific effects were observed; the signals were stronger, compared to the relative intensities in the one-photon absorption spectrum, for irradiation on the aromatic (phenyl) C-H stretch transitions, rather than those involving aliphatic (backbone) C-H modes. The applicability of mid-IR resonance enhanced LIBS for detection of residues on surfaces is discussed.

  20. Laser-induced breakdown spectroscopy with laser irradiation resonant with vibrational transitions

    SciTech Connect

    Khachatrian, Ani; Dagdigian, Paul J.

    2010-05-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of polymers, both in bulk form and spin coated on Si wafers, with laser irradiation in the mid-infrared spectral region is presented. Of particular interest is whether the LIBS signals are enhanced when the laser wavelength is resonant with a fundamental vibrational transition of the polymer. Significant increases in the LIBS signals were observed for irradiation on hydride stretch fundamental transitions, and the magnitude of the enhancement showed a strong dependence on the mode excited. The role of the substrate was investigated by comparison of results for bulk and spin-coated samples. The polymers investigated were Nylon 12 and poly(vinyl alcohol-co-ethylene).

  1. Laser-induced heat diffusion limited tissue coagulation as a laser therapy mode

    NASA Astrophysics Data System (ADS)

    Lubashevsky, Ihor A.; Priezzhev, Alexander V.; Gafiychuk, Vasyl V.

    2000-11-01

    Previously we have developed a free boundary model for local thermal coagulation induced by laser light absorption when the tissue region affected directly by laser light is sufficiently small and heat diffusion into the surrounding tissue governs the necrosis growth. In the present paper keeping in mind the obtained results we state the point of view on the necrosis formation under these conditions as the basis of an individual laser therapy mode exhibiting specific properties. In particular, roughly speaking, the size of the resulting necrosis domain is determined by the physical characteristics of the tissue and its response to local heating, and by the applicator form rather than the treatment duration and the irradiation power.

  2. Laser-induced fluorescence detection of hot molecular oxygen in flames using an alexandrite laser.

    PubMed

    Kiefer, Johannes; Zhou, Bo; Zetterberg, Johan; Li, Zhongshan; Alden, Marcus

    2014-01-01

    The use of an alexandrite laser for laser-induced fluorescence (LIF) spectroscopy and imaging of molecular oxygen in thermally excited vibrational states is demonstrated. The laser radiation after the third harmonic generation was used to excite the B-X (0-7) band at 257 nm in the Schumann-Runge system of oxygen. LIF emission was detected between 270 and 380 nm, revealing distinct bands of the transitions from B(0) to highly excited vibrational states in the electronic ground state, X (v > 7). At higher spectral resolution, these bands reveal the common P- and R-branch line splitting. Eventually, the proposed LIF approach was used for single-shot imaging of the two-dimensional distribution of hot oxygen molecules in flames. PMID:25279538

  3. Low-reflectance laser-induced surface nanostructures created with a picosecond laser

    NASA Astrophysics Data System (ADS)

    Sarbada, Shashank; Huang, Zhifeng; Shin, Yung C.; Ruan, Xiulin

    2016-04-01

    Using high-speed picosecond laser pulse irradiation, low-reflectance laser-induced periodic surface structures (LIPSS) have been created on polycrystalline silicon. The effects of laser fluence, scan speed, overlapping ratio and polarization angle on the formation of LIPSS are reported. The anti-reflective properties of periodic structures are discussed, and the ideal LIPSS for low surface reflectance is presented. A decrease of 35.7 % in average reflectance of the silicon wafer was achieved over the wavelength range of 400-860 nm when it was textured with LIPSS at high scan speeds of 4000 mm/s. Experimental results of broadband reflectance of silicon wafers textured with LIPSS have been compared with finite difference time domain simulations and are in good agreement, showing high predictability in reflectance values for different structures. The effects of changing the LIPSS profile, fill factor and valley depth on the surface reflectance were also analyzed through simulations.

  4. Detection of trace phosphorus in steel using laser-induced breakdown spectroscopy combined with laser-induced fluorescence

    SciTech Connect

    Shen, X. K.; Wang, H.; Xie, Z. Q.; Gao, Y.; Ling, H.; Lu, Y. F.

    2009-05-01

    Monitoring of light-element concentration in steel is very important for quality assurance in the steel industry. In this work, detection in open air of trace phosphorus (P) in steel using laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) has been investigated. An optical parametric oscillator wavelength-tunable laser was used to resonantly excite the P atoms within plasma plumes generated by a Q-switched Nd:YAG laser. A set of steel samples with P concentrations from 3.9 to 720 parts in 10{sup 6}(ppm) were analyzed using LIBS-LIF at wavelengths of 253.40 and 253.56 nm for resonant excitation of P atoms and fluorescence lines at wavelengths of 213.55 and 213.62 nm. The calibration curves were measured to determine the limit of detection for P in steel, which is estimated to be around 0.7 ppm. The results demonstrate the potential of LIBS-LIF to meet the requirements for on-line analyses in open air in the steel industry.

  5. Detection of trace phosphorus in steel using laser-induced breakdown spectroscopy combined with laser-induced fluorescence.

    PubMed

    Shen, X K; Wang, H; Xie, Z Q; Gao, Y; Ling, H; Lu, Y F

    2009-05-01

    Monitoring of light-element concentration in steel is very important for quality assurance in the steel industry. In this work, detection in open air of trace phosphorus (P) in steel using laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) has been investigated. An optical parametric oscillator wavelength-tunable laser was used to resonantly excite the P atoms within plasma plumes generated by a Q-switched Nd:YAG laser. A set of steel samples with P concentrations from 3.9 to 720 parts in 10(6) (ppm) were analyzed using LIBS-LIF at wavelengths of 253.40 and 253.56 nm for resonant excitation of P atoms and fluorescence lines at wavelengths of 213.55 and 213.62 nm. The calibration curves were measured to determine the limit of detection for P in steel, which is estimated to be around 0.7 ppm. The results demonstrate the potential of LIBS-LIF to meet the requirements for on-line analyses in open air in the steel industry. PMID:19412215

  6. Silicone oil pupil block glaucoma in a pseudophakic eye

    PubMed Central

    Yusuf, Imran H; Fung, Timothy H M; Salmon, John F; Patel, Chetan Kantibhai

    2014-01-01

    Intravitreal silicone oil achieves an effective endotamponade in patients with complex retinal detachments. Silicone oil displacement into the anterior chamber risks glaucoma and endothelial failure. We describe a 52-year-old patient with pseudophakia with silicone oil endotamponade presenting with visual loss and intraocular pressure of 60 mm Hg. Inferior YAG iridotomy was undertaken to repatriate silicone oil to the posterior segment. Despite normal intraocular pressure, acute corneal oedema occurred postiridotomy, resolving spontaneously over 2 weeks. Pupil block glaucoma secondary to silicone oil requires a management approach based on an understanding of silicone oil fluidics. Careful selection of inferior laser iridotomy site is critical to effectively reverse pupil block. Anterior migration of silicone oil in patients with pseudophakia is rare. We offer an hypothesis to explain unanticipated transient corneal oedema following silicone oil displacement from the anterior chamber. Clinicians must discuss the possibility of transient or permanent endothelial failure preoperatively in this patient group. PMID:25249219

  7. Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

    SciTech Connect

    Pan, A.; Dias, A.; Gomez-Aranzadi, M.; Olaizola, S. M.; Rodriguez, A.

    2014-05-07

    The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.

  8. Laser-induced growth of nanocrystals embedded in porous materials

    PubMed Central

    2013-01-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  9. Laser-induced fluorescence in diagnosis of dental caries

    NASA Astrophysics Data System (ADS)

    Drakaki, Eleni A.; Makropoulou, Mersini I.; Khabbaz, Maruan; Serafetinides, Alexandros A.

    2003-09-01

    laser induces better discrimination in deep caries diagnosis.

  10. Laser-induced growth of nanocrystals embedded in porous materials

    NASA Astrophysics Data System (ADS)

    Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed

    2013-06-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  11. Imaging laser-induced thermal fields and effects

    NASA Astrophysics Data System (ADS)

    Verdaasdonck, Rudolf M.

    1995-05-01

    Laser light interaction with biological tissues is a combination of optical, thermal and mechanical effects depending on the energy applied per unit of volume per unit of time. Visualization of the phenomena with a high temporal and spatial resolution, contributes to a better understanding of the mechanism of action, especially when pulsed lasers are involved. For this goal, setups were developed based on Schlieren techniques to image the interaction of pulsed (CO2, Holmium and Excimer) and CW (CO2, Nd:YAG, Cu-vapor) lasers with physiological media and biological tissues. In a 'fast' Schlieren setup, images of shock waves and fast expanding and imploding vapor bubbles were captured using very short light flashes (10 ns-10 microseconds). These recordings suggest that these explosive vapor bubbles seem to be the main dynamism for tissue ablation. In a 'color' Schlieren setup, very small changes in optical density of the media induced by temperature gradients, were color coded. Calibration of the color images to absolute temperatures were performed by using calculated temperature distributions and by thermocouple measurements. Cameras with high speed shutters (0.1-50 ms) enabled the recording of dynamic images of the thermal relaxation and heat diffusion in tissues during variation of pulse length and repetition rate. Despite pulse lengths < ms, heat generation in tissue was considerable already at pulse repetition rates above a few Hz. Similar Schlieren techniques were applied to study the thermal characteristics of laser probes, e.g. for the treatment of Benign Prostatic Hyperplasia (BPH). In combination with thermal modeling an optimal therapy might be predicted. Schlieren techniques, generating high-speed and 'thermal' images, can provide a good understanding of the ablation mechanism and the thermo-dynamics during laser-tissue interaction with continuous wave and pulse lasers.

  12. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  13. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy.

    PubMed

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications. PMID:27036765

  14. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.

  15. Surface modifications induced by pulsed-laser texturing—Influence of laser impact on the surface properties

    NASA Astrophysics Data System (ADS)

    Costil, S.; Lamraoui, A.; Langlade, C.; Heintz, O.; Oltra, R.

    2014-01-01

    Laser cleaning technology provides a safe, environmentally friendly and very cost effective way to improve cleaning and surface preparation of metallic materials. Compared with efficient cleaning processes, it can avoid the disadvantages of ductile materials prepared by conventional technologies (cracks induced by sand-blasting for example) and treat only some selected areas (due to the optical fibers). By this way, laser technology could have several advantages and expand the range of thermal spraying. Moreover, new generations of lasers (fiber laser, disc laser) allow the development of new methods. Besides a significant bulk reduction, no maintenance, low operating cost, laser fibers can introduce alternative treatments. Combining a short-pulse laser with a scanner allows new applications in terms of surface preparation. By multiplying impacts using scanning laser, it is possible to shape the substrate surface to improve the coating adhesion as well as the mechanical behaviour.

  16. Prevention of Blindness: Chronic Glaucoma

    ERIC Educational Resources Information Center

    Richardson, Kenneth T.

    1970-01-01

    An evaluation of present screening procedures for chronic open-angle glaucoma includes suggestions for improvement: greater distribution of screening and education, conversion from monophasic to multiphasic screen, and examination of visual fields, optic nerve, and medical history in addition to the tonometry currently done. (KW)

  17. Optical Coherence Tomography in Glaucoma

    NASA Astrophysics Data System (ADS)

    Berisha, Fatmire; Hoffmann, Esther M.; Pfeiffer, Norbert

    Retinal nerve fiber layer (RNFL) thinning and optic nerve head cupping are key diagnostic features of glaucomatous optic neuropathy. The higher resolution of the recently introduced SD-OCT offers enhanced visualization and improved segmentation of the retinal layers, providing a higher accuracy in identification of subtle changes of the optic disc and RNFL thinning associated with glaucoma.

  18. [The Progress in Remote Laser-Induced Breakdown Spectroscopy].

    PubMed

    Zhang, Ting-ting; Wan, Xiong; Shu, Rong; Liu, Peng-xi

    2015-07-01

    As a kind of spectroscopic technique, the remote laser-induced breakdown spectroscopy (Remote LIBS) can measure elemental compositions of remote targets by using high-power lasers and focusing approaches. In this paper, three remote detection approaches (open path LIBS, fiber optic LIBS and compact probe fiber optic LIBS) and their system architectures are summarized and analyzed. Conventional open path LIBS, with high requirement of specifications of lasers, optical systems, spectrographs and detectors, has always been a research focus in remote testing field. Fiber optic LIBS has the advantages of simplification of optical focusing system and high collection efficiency of the plasma light. This paper reviews the progress in new techniques of LIBS, for instance Filament-LIBS techniques and LIBS combines with other spectral detection techniques, and emphatically analyzes their characteristics and advantages. These new techniques have greatly broadened the detection range of LIBS, enhanced material recognition ability of LIBS, and made a great contribution to expanding applications of remote LIBS. Latest development of applications of remote LIBS in fields of deep space exploration, hazardous material detection, pollution testing, metallurgical industries and heritage restoration is introduced in detail. With the development of laser techniques, spectral detection and calibration techniques, the detection range of remote LIBS has been expended, their application fields has been extended, and the detection precision and accuracy have been improved. PMID:26717768

  19. Construction of a Laser Induced Breakdown Spectroscopy Setup

    NASA Astrophysics Data System (ADS)

    Mays, Joseph; Palmer, Andria; Amos, James; Dynka, Tom; Ujj, Lazlo

    Laser Induced Breakdown Spectroscopy (LIBS) is a practical spectroscopy to determine the chemical and atomic composition of materials. The third harmonic output of a Nd:YAG Q-switched laser generating 5ns pulses with 10Hz repetition rate was used to ablate the sample and create a micro-plasma. The emission of the radiating plasma was focused into an optical fiber with 0.22 numerical aperture. The spectra was measured with an Ocean Optics micro spectrometer. A synchronized shutter was used to select single laser pulses. In order to reach the breakdown threshold of the sample using the available energy of the laser pulses (<5 mJ) a beam expander and a parabolic mirror was used for tight focusing. The optical and technical details including the characterization of the system will be presented. LIBS spectra taken from a variety of metal and organic samples show appropriate selectivity for quantitative and qualitative analysis for materials. UWF NIH MARC U-STAR 1T34GM110517-01, UWF Office of Undergraduate Research.

  20. Liquid explosions induced by X-ray laser pulses

    NASA Astrophysics Data System (ADS)

    Stan, Claudiu A.; Milathianaki, Despina; Laksmono, Hartawan; Sierra, Raymond G.; McQueen, Trevor A.; Messerschmidt, Marc; Williams, Garth J.; Koglin, Jason E.; Lane, Thomas J.; Hayes, Matt J.; Guillet, Serge A. H.; Liang, Mengning; Aquila, Andrew L.; Willmott, Philip R.; Robinson, Joseph S.; Gumerlock, Karl L.; Botha, Sabine; Nass, Karol; Schlichting, Ilme; Shoeman, Robert L.; Stone, Howard A.; Boutet, Sébastien

    2016-10-01

    Explosions are spectacular and intriguing phenomena that expose the dynamics of matter under extreme conditions. We investigated, using time-resolved imaging, explosions induced by ultraintense X-ray laser pulses in water drops and jets. Our observations revealed an explosive vaporization followed by high-velocity interacting flows of liquid and vapour, and by the generation of shock trains in the liquid jets. These flows are different from those previously observed in laser ablation, owing to a simpler spatial pattern of X-ray absorption. We show that the explosion dynamics in our experiments is consistent with a redistribution of absorbed energy, mediated by a pressure or shock wave in the liquid, and we model the effects of explosions, including their adverse impact on X-ray laser experiments. X-ray laser explosions have predictable dynamics that may prove useful for controlling the state of pure liquids over broad energy scales and timescales, and for triggering pressure-sensitive molecular dynamics in solutions.

  1. Dust Removal on Mars Using Laser-Induced Breakdown Spectroscopy

    NASA Technical Reports Server (NTRS)

    Graff, T. G.; Morris, R. V.; Clegg, S. M.; Wiens, R. C.; Anderson, R. B.

    2011-01-01

    Dust coatings on the surface of Mars complicate and, if sufficiently thick, mask the spectral characteristics and compositional determination of underlying material from in situ and remote sensing instrumentation. The Laser-Induced Breakdown Spectroscopy (LIBS) portion of the Chemistry & Camera (ChemCam) instrument, aboard the Mars Science Laboratory (MSL) rover, will be the first active remote sensing technique deployed on Mars able to remove dust. ChemCam utilizes a 5 ns pulsed 1067 nm high-powered laser focused to less than 400 m diameter on targets at distances up to 7 m [1,2]. With multiple laser pulses, dust and weathering coatings can be remotely analyzed and potentially removed using this technique [2,3]. A typical LIBS measurement during MSL surface operations is planned to consist of 50 laser pulses at 14 mJ, with the first 5 to 10 pulses used to analyze as well as remove any surface coating. Additionally, ChemCam's Remote Micro-Imager (RMI) is capable of resolving 200 m details at a distance of 2 m, or 1 mm at 10 m [1,4]. In this study, we report on initial laboratory experiments conducted to characterize the removal of dust coatings using similar LIBS parameters as ChemCam under Mars-like conditions. These experiments serve to better understand the removal of surface dust using LIBS and to facilitate the analysis of ChemCam LIBS spectral data and RMI images.

  2. Optofluidic tunable lenses using laser-induced thermal gradient.

    PubMed

    Chen, Qingming; Jian, Aoqun; Li, Zhaohui; Zhang, Xuming

    2016-01-01

    This paper reports a new design of optofluidic tunable lens using a laser-induced thermal gradient. It makes use of two straight chromium strips at the bottom of the microfluidic chamber to absorb the continuous pump laser to heat up the moving benzyl alcohol solution, creating a 2D refractive index gradient in the entrance part between the two hot strips. This design can be regarded as a cascade of a series of refractive lenses, and is distinctively different from the reported liquid lenses that mimic the refractive lens design and the 1D gradient index lens design. CFD simulation shows that a stable thermal lens can be built up within 200 ms. Experiments were conducted to demonstrate the continuous tuning of focal length from initially infinite to the minimum 1.3 mm, as well as the off-axis focusing by offsetting the pump laser spot. Data analyses show the empirical dependences of the focal length on the pump laser intensity and the flow velocity. Compared with previous studies, this tunable lens design enjoys many merits, such as fast tuning speed, aberration-free focusing, remote control, and enabling the use of homogeneous fluids for easy integration with other optofluidic systems. PMID:26584422

  3. Laser induced focusing for over-dense plasma beams

    SciTech Connect

    Schmidt, Peter; Boine-Frankenheim, Oliver; Mulser, Peter

    2015-09-15

    The capability of ion acceleration with high power, pulsed lasers has become an active field of research in the past years. In this context, the radiation pressure acceleration (RPA) mechanism has been the topic of numerous theoretical and experimental publications. Within that mechanism, a high power, pulsed laser beam hits a thin film target. In contrast to the target normal sheath acceleration, the entire film target is accelerated as a bulk by the radiation pressure of the laser. Simulations predict heavy ion beams with kinetic energy up to GeV, as well as solid body densities. However, there are several effects which limit the efficiency of the RPA: On the one hand, the Rayleigh-Taylor-instability limits the predicted density. On the other hand, conventional accelerator elements, such as magnetic focusing devices are too bulky to be installed right after the target. Therefore, we present a new beam transport method, suitable for RPA-like/over-dense plasma beams: laser induced focusing.

  4. In vivo laser-induced breakdown in the rabbit eye

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; DiCarlo, Cheryl D.; Kennedy, Paul K.; Noojin, Gary D.; Amnotte, Rodney E.; Roach, William P.

    1995-05-01

    Threshold measurements for femtosecond laser pulsewidths have been made for retinal minimum visible lesions (MVLs) in Dutch Belted rabbit and rhesus monkey eyes. Laser-induced breakdown (LIB) thresholds in biological materials including vitreous, normal saline, tap water, and ultrapure water have been measured and reported using an artificial eye. We have recorded on video the first LIB causing bubble formation in any eye in vivo using albino rabbit eyes (New Zealand white) with 120- femtosecond (fs) pulses and pulse energies as low as 5 microjoules ((mu) J). These bubbles were clearly formed anterior to the retina within the vitreous humor and, with 60 (mu) J of energy, they lasted for several seconds before disappearing and leaving no apparent damage to the retina. We believe this to be true LIB because of the lack of pigmentation or melanin granules within the albino rabbit eye (thus no absorptive elements) and because of the extremely high peak powers within the 5-(mu) J, 120-fs laser pulse. These high peak powers produce self-focusing of the pulse within the vitreous. The bubble formation at the breakdown site acts as a limiting mechanism for energy transmission and may explain why high-energy femotsecond pulses at energies up to 100 (mu) J sometimes do not cause severe damage in the pigmented rabbit eye. This fact may also explain why it is so difficult to produce hemorrhagic lesions in either the rabbit or primate eye with 100-fs laser pulses.

  5. Laser-induced forward transfer (LIFT) of congruent voxels

    NASA Astrophysics Data System (ADS)

    Piqué, Alberto; Kim, Heungsoo; Auyeung, Raymond C. Y.; Beniam, Iyoel; Breckenfeld, Eric

    2016-06-01

    Laser-induced forward transfer (LIFT) of functional materials offers unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements. The use of LIFT for printing high viscosity metallic nano-inks and nano-pastes can be optimized for the transfer of voxels congruent with the shape of the laser pulse, forming thin film-like structures non-lithographically. These processes are capable of printing patterns with excellent lateral resolution and thickness uniformity typically found in 3-dimensional stacked assemblies, MEMS-like structures and free-standing interconnects. However, in order to achieve congruent voxel transfer with LIFT, the particle size and viscosity of the ink or paste suspensions must be adjusted to minimize variations due to wetting and drying effects. When LIFT is carried out with high-viscosity nano-suspensions, the printed voxel size and shape become controllable parameters, allowing the printing of thin-film like structures whose shape is determined by the spatial distribution of the laser pulse. The result is a new level of parallelization beyond current serial direct-write processes whereby the geometry of each printed voxel can be optimized according to the pattern design. This work shows how LIFT of congruent voxels can be applied to the fabrication of 2D and 3D microstructures by adjusting the viscosity of the nano-suspension and laser transfer parameters.

  6. [Surgical indications in coexisting cataracts and glaucoma].

    PubMed

    Collignon-Brach, J D; Ravet, O; Robe-Collignon, N

    2000-01-01

    Cataract surgery in glaucoma patients remains a controversial subjects. Indication of surgery depends on a lot of clinical parameters: diagnosis, state, evolution of glaucoma as well as compliance with medical treatment--surgical procedures of cataract and glaucoma--sites of the surgery--use of antifibrosis agents and surgeon's experience. As cataract extraction alone decreases the intraocular pressure in open angle glaucoma and mainly in uncomplicated closed angle glaucoma and trabeculectomy alone reduces the intraocular pressure more than combined surgery with less complications we recommended the following surgical options: Cataract extraction alone in patients with controlled open angle glaucoma and in patients with closed angle glaucoma. A two step procedure: filtering surgery followed by cataract extraction in patients with poorly controlled open angle glaucoma or mixed closed angle glaucoma. Ambulatory surgery and topical anesthesia permit a two stages surgery with less inconveniences. A combined procedure in patients with a chronic closed angle glaucoma where filtering procedure alone is associated with important complications. Actually, the best surgical cataract procedure is phacoemulsification with a small supero-corneal incision and implantation of a foldable intraocular lens. The best filtering procedure remains trabeculectomy, or the new non penetrating trabecular surgery for experimented surgeons, in the superior quadrant. In the future new surgical procedures and new safe and non toxic pharmacologic drugs which modulate wound healing could be found in order to increase the efficacity and indications of combined surgery. PMID:11262885

  7. Corneal hysteresis and its relevance to glaucoma

    PubMed Central

    Deol, Madhvi; Taylor, David A.; Radcliffe, Nathan M.

    2015-01-01

    Purpose of review Glaucoma is a leading cause of irreversible blindness worldwide. It is estimated that roughly 60.5 million people had glaucoma in 2010 and that this number is increasing. Many patients continue to lose vision despite apparent disease control according to traditional risk factors. The purpose of this review is to discuss the recent findings with regard to corneal hysteresis, a variable that is thought to be associated with the risk and progression of glaucoma. Recent findings Low corneal hysteresis is associated with optic nerve and visual field damage in glaucoma and the risk of structural and functional glaucoma progression. In addition, hysteresis may enhance intraocular pressure (IOP) interpretation: low corneal hysteresis is associated with a larger magnitude of IOP reduction following various glaucoma therapies. Corneal hysteresis is dynamic and may increase in eyes after IOP-lowering interventions are implemented. Summary It is widely accepted that central corneal thickness is a predictive factor for the risk of glaucoma progression. Recent evidence shows that corneal hysteresis also provides valuable information for several aspects of glaucoma management. In fact, corneal hysteresis may be more strongly associated with glaucoma presence, risk of progression, and effectiveness of glaucoma treatments than central corneal thickness. PMID:25611166

  8. Femtosecond laser induced nanostructuring for surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Messaoudi, H.; Das, S. K.; Lange, J.; Heinrich, F.; Schrader, S.; Frohme, M.; Grunwald, R.

    2014-03-01

    The formation of periodical nanostructures with femtosecond laser pulses was used to create highly efficient substrates for surface-enhanced Raman spectroscopy (SERS). We report about the structuring of silver and copper substrates and their application to the SERS of DNA (herring sperm) and protein molecules (egg albumen). The maximum enhancement factors were found on Ag substrates processed with the second harmonic generation (SHG) of a 1-kHz Ti:sapphire laser and structure periods near the SHG wavelength. In the case of copper, however, the highest enhancement was obtained with long-period ripples induced with at fundamental wavelength. This is explained by an additional significant influence of nanoparticles on the surface. Nanostructured areas in the range of 1.25 mm2 were obtained in 10 s. The surfaces were characterized by scanning electron microscopy, Fast Fourier Transform and Raman spectroscopy. Moreover, the role of the chemical modification of the metal structures is addressed. Thin oxide layers resulting from working in atmosphere which improve the biocompatibility were indicated by vibration spectra. It is expected that the detailed study of the mechanisms of laser-induced nanostructure formation will stimulate further applications of functionalized surfaces like photocatalysis, selective chemistry and nano-biology.

  9. Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation

    SciTech Connect

    Gebauer, Bernhard Tunn, Per-Ulf; Gaffke, Gunnar; Melcher, Ingo; Felix, Roland; Stroszczynski, Christian

    2006-04-15

    The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

  10. Glaucoma in a New Zealand White Rabbit Fed High-cholesterol Diet

    PubMed Central

    Kashiwagi, Emi; Masuno, Koichi; Fujisawa, Kae; Matsushima, Shuuichi; Torii, Mikinori; Takasu, Nobuo

    2012-01-01

    Goniodysgenesis, malformation of the filtration angle, was observed in a New Zealand white rabbit supplied with 100 g/day rabbit chow containing 0.2% cholesterol for 10 months. Histopathology revealed cupping of the optic disc, atrophy of the retina and hyalinization of the ciliary body in the bilateral eyeballs. These findings corresponded with histopathological features caused by glaucoma. On the basis of these findings, we diagnosed this lesion as glaucoma, and classified it as primary glaucoma because of the presence of developmental defects of the filtration angle. In this case, hypercholesterolemia-induced changes, such as aggregation of lipid-laden macrophages and cholesterin clefts in the sclera or choroid, might cause deterioration of the lesions in glaucoma. PMID:22481859

  11. Formation of carbon nanotubes: In situ optical analysis using laser-induced incandescence and laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Cau, M.; Dorval, N.; Attal-Trétout, B.; Cochon, J.-L.; Foutel-Richard, A.; Loiseau, A.; Krüger, V.; Tsurikov, M.; Scott, C. D.

    2010-04-01

    Gas-phase production of carbon nanotubes in presence of a metal catalyst with a continuous wave CO2 laser is investigated by combining coherent anti-Stokes Raman scattering (CARS), laser-induced fluorescence (LIF), and laser-induced incandescence (LII). These in situ techniques provide a unique investigation of the different transformation processes of the primarily carbon and metal vapors issued from the vaporization of the target by the laser and the temperature at which these processes occur. Continuous-wave laser provides with stable continuous vaporization conditions very well suited for such in situ investigations. Temperature profiles inside the reactor are known from CARS measurements and flow calculations. Carbon soot, density, and size of carbon aggregates are determined by LII measurements. LIF measurements are used to study the gas phases, namely, C2 and C3 radicals which are the very first steps of carbon recombination, and metal catalysts gas phase. Spectral investigations allow us to discriminate the signal from each species by selecting the correct pair of excitation/detection wavelengths. Spatial distributions of the different species are measured as a function of target composition and temperature. The comparison of LIF and LII signals allow us to correlate the spatial evolution of gas and soot in the scope of the different steps of the nanotube growth already proposed in the literature and to identify the impact of the chemical nature of the catalyst on carbon condensation and nanotube nucleation. Our study presents the first direct evidence of the nanotube onset and that the nucleation proceeds from a dissolution-segregation process from metal particles as assumed in the well-known vapor-liquid-solid model. Comparison of different catalysts reveals that this process is strongly favored when Ni is present.

  12. Laser ablation laser induced fluorescence for sensitive detection of heavy metals in water

    NASA Astrophysics Data System (ADS)

    Godwal, Yogesh

    Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the first pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (≤ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy single-pulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 muJ and an excitation laser pulse energy of 8 muJ. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the effect of detector gain, the gate delay and the gate width were studied. In

  13. Drainage devices in glaucoma surgery.

    PubMed

    Hille, K; Moustafa, B; Hille, A; Ruprecht, K W

    2004-01-01

    Glaucoma drainage devices, also termed aqueous shunts (AS), are widely used in the USA. Indications for AS include excessive conjunctival scarring diminishing the success of another filtration surgeries, abnormalities of the iridocorneal angle, neovascular glaucoma, presence of corneal grafts, and inflammatory glaucoma. Qualified success has been achieved for many years in 50 to 100 % of the treated eyes, depending on the patient selection. An AS consists of a silicone tube that is inserted into the anterior chamber and a plate (explant) made of silicone or polypropylene. The latter is positioned between the recti muscles. Within some weeks the surrounding tissue forms a fibrous bleb around the plate. This serves as a permanent filtration reservoir. The most serious complication is postoperative hypotonia, that can lead to serious choroidal detachment, suprachoroidal hemorrhage, anterior chamber flattening, and corneal decompensation. To avoid this complication some devices, e.g. the Ahmed Glaucoma valve and the Krupin valve, have integrated mechanisms to sustain a residual intraocular pressure. With other devices such as the Molteno and the Baerveldt devices the tube has to be temporarily ligated until a scar area forms around the explant. On the other hand, fibrous infiltration of the wall of the bleb often leads to a reversible rise in intraocular pressure about one to four months after surgery which can be treated by massaging the bulb, needling the bleb, or injection of antimetabolites. There are no obvious differences between the different AS regarding the success of pressure control. With appreciation of indications and therapy of complications, AS are an useful option in the management of complicated glaucoma, where conventional filtration surgery is considered to carry a high risk of failure.

  14. Enhancement of airborne shock wave by laser-induced breakdown of liquid column in laser shock cleaning

    SciTech Connect

    Jang, Deoksuk; Kim, Dongsik; Park, Jin-Goo

    2011-04-01

    In laser shock cleaning (LSC), the shock wave is generated by laser-induced breakdown of the ambient gas. The shock wave intensity has thus been a factor limiting the performance of the LSC process. In this work, a novel method of amplifying a laser-induced plasma-generated shock wave by the breakdown of a liquid column is proposed and analyzed. When the laser beam is focused on a microscale liquid column, a shock wave having a significantly amplified intensity compared to that generated by air breakdown alone can be generated in air. Therefore, substantially amplified cleaning force can be obtained. The dynamics of a shock wave induced by a Q-switched Nd:YAG laser was analyzed by laser flash shadowgraphy. The peak pressure of the laser-induced shock wave was approximately two times greater than that of air breakdown at the same laser fluence. The proposed method of shock wave generation is expected to be useful in various applications of laser shock processing, including surface cleaning.

  15. Analysis of fresco by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Caneve, L.; Diamanti, A.; Grimaldi, F.; Palleschi, G.; Spizzichino, V.; Valentini, F.

    2010-08-01

    The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition. The depth profiling permitted to put in evidence the presence of successive paint layers with different compositions. A comparison with the results obtained by the microscopy inspection of the sample has been done.

  16. Stimulated emission and lasing in laser-induced plasma plume

    NASA Astrophysics Data System (ADS)

    Nagli, Lev; Gaft, Michael; Gornushkin, Igor; Glaus, Reto

    2016-11-01

    The lasing effect is demonstrated in laser plasmas induced on various metal targets and pumped by a laser tuned in resonance with a strong optical transition of a metal. The intense, polarized and low-divergent radiation is emitted from a longitudinally pumped plasma plume in forward and backward directions with respect to the pump beam. Lasing occurs only within duration of the pumping pulse. The effect is found for elements of 13th and 14th groups and for Ca, Ti, Zr, Fe and Ni. The Einstein coefficients for spontaneous emission of all lasing transitions are higher than 107 s-1. For some elements like Al and In, a three-level lasing scheme is realized. For others, like Tl, both three- and four-level lasing schemes are realized. It is found that the longitudinal pump geometry is more efficient than the transversal one.

  17. Laser-induced vibration of a thin soap film.

    PubMed

    Emile, Olivier; Emile, Janine

    2014-09-21

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems. PMID:25017934

  18. Laser-induced breakdown spectroscopy for elemental analysis

    SciTech Connect

    Loree, T.R.

    1984-01-01

    Laser-Induced Breakdown Spectroscopy, or LIBS, is a laser-based form of atomic emission spectroscopy that can be used for the in-situ elemental analysis of coal gasifier product streams. At this point, LIBS has been deployed in three gasifier field tests, and C, H, O, N, Na, K, S, Cr, Cu, Fe, Mg, Pb, Se, Al, Ba, Ca, Cd, Li, and Mn were qualitatively detected in the various product streams. In laboratory experiments on quantitative detection, a detection limit of 4 ppB was demonstrated for sodium. The long-range goal of this program is add the trace elements As, B, Mo, Ni, V, and Zn to the detection list, and to develop the capability of quantitative detection in real time for the trace elements. 4 figures.

  19. Laser-induced propagation and destruction of amyloid beta fibrils.

    PubMed

    Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

    2010-06-18

    The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

  20. Laser-induced fluorescence spectroscopy in tissue local necrosis detection

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Buchta, Zdenek; Lesundak, Adam; Randula, Antonin; Mikel, Bretislav; Lazar, Josef; Veverkova, Lenka

    2014-03-01

    The recent effort leads to reliable imaging techniques which can help to a surgeon during operations. The fluorescence spectroscopy was selected as very useful online in vivo imaging method to organics and biological materials analysis. The presented work scopes to a laser induced fluorescence spectroscopy technique to detect tissue local necrosis in small intestine surgery. In first experiments, we tested tissue auto-fluorescence technique but a signal-to-noise ratio didn't express significant results. Then we applied a contrast dye - IndoCyanine Green (ICG) which absorbs and emits wavelengths in the near IR. We arranged the pilot experimental setup based on highly coherent extended cavity diode laser (ECDL) used for stimulating of some critical areas of the small intestine tissue with injected ICG dye. We demonstrated the distribution of the ICG exciter with the first file of shots of small intestine tissue of a rabbit that was captured by high sensitivity fluorescent cam.

  1. Laser-induced damage thresholds of starched PMMA waveplates

    NASA Astrophysics Data System (ADS)

    Melninkaitis, A.; Mikšys, D.; Maciulevičius, M.; Sirutkaitis, V.; Šlekys, G.; Samoylov, A. V.

    2007-01-01

    Polymethyl methacrylate (PMMA) is a versatile polymeric material that is well suited for fabrication of many commercial optical components: lenses, fibers, windows, phase waveplates and others. Our focus is achromatic zero-order waveplates made of anisotropic PMMA which can be used to modify the state of polarization of electromagnetic radiation. Such waveplates have a broad range of application in devices where polarized radiation is used. For example, when tunable lasers are used or when spectropolarimetric measurements are performed, one needs an achromatic waveplate providing a specific retardation in a wide wavelength range. Herewith anisotropic properties of PMMA subjected to one-axis stretching are analyzed and the technology for manufacturing such achromatic and super-achromatic, one-axis-stretched PMMA waveplates is described. This technology excludes any mechanical processing of waveplate component surfaces. Technical characteristics of achromatic and super-achromatic waveplates manufactured of PMMA including results of laser-induced damage threshold (LIDT) measurements are discussed below.

  2. Microfabrication of polystyrene microbead arrays by laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, Alexandra; Dinca, Valentina; Paraico, Iurie; Moldovan, Antoniu; Shaw-Stewart, James; Schneider, Christof W.; Kovacs, Eugenia; Lippert, Thomas; Dinescu, Maria

    2010-08-01

    In this study we describe a simple method to fabricate microarrays of polystyrene microbeads (PS-μbeads) on Thermanox coverslip surfaces using laser induced forward transfer (LIFT). A triazene polymer layer which acts as a dynamic release layer and propels the closely packed microspheres on the receiving substrate was used for this approach. The deposited features were characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. Ultrasonication was used to test the adherence of the transferred beads. In addition, the laser ejection of the PS-μbead pixels was investigated by time resolved shadowgraphy. It was found that stable PS-μbeads micropatterns without any specific immobilization process could be realized by LIFT. These results highlight the increasing role of LIFT in the development of biomaterials, drug delivery, and tissue engineering.

  3. Laser-induced vibration of a thin soap film.

    PubMed

    Emile, Olivier; Emile, Janine

    2014-09-21

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems.

  4. Enhanced Spore Biomarker Detection Following Laser Induced Lysis

    SciTech Connect

    Wunschel, David S.; Beck, Kenneth M.; Wahl, Karen L.

    2002-12-01

    Matrix assisted laser desorption/ionization (MALDI) has grown in popularity as a means to rapidly analyze proteins directly from bacterial cells. This method provides identifying information by generating protein ?fingerprints? for each organism. However, generating rich protein fingerprints from spores, such as from the genus Bacillus, has proven difficult. We have examined the use of laser energy to induce spore lysis and increase the protein signature complexity. As a measure of lysis, the ions from calcium and dipicolinic acid (DPA) were monitored along with the higher m/z protein ions. DPA is a known marker of eubacterial spores usually as a complex with calcium. This is in contrast to the abundant geogenic calcium complexes with carbonate among other forms. A combination of general bacterial markers, DPA and calcium, and protein fingerprints can be used to provide complementary biomarkers from a single sample preparation.

  5. Laser induced heat source distribution in bio-tissues

    NASA Astrophysics Data System (ADS)

    Li, Xiaoxia; Fan, Shifu; Zhao, Youquan

    2006-09-01

    During numerical simulation of laser and tissue thermal interaction, the light fluence rate distribution should be formularized and constituted to the source term in the heat transfer equation. Usually the solution of light irradiative transport equation is given in extreme conditions such as full absorption (Lambert-Beer Law), full scattering (Lubelka-Munk theory), most scattering (Diffusion Approximation) et al. But in specific conditions, these solutions will induce different errors. The usually used Monte Carlo simulation (MCS) is more universal and exact but has difficulty to deal with dynamic parameter and fast simulation. Its area partition pattern has limits when applying FEM (finite element method) to solve the bio-heat transfer partial differential coefficient equation. Laser heat source plots of above methods showed much difference with MCS. In order to solve this problem, through analyzing different optical actions such as reflection, scattering and absorption on the laser induced heat generation in bio-tissue, a new attempt was made out which combined the modified beam broaden model and the diffusion approximation model. First the scattering coefficient was replaced by reduced scattering coefficient in the beam broaden model, which is more reasonable when scattering was treated as anisotropic scattering. Secondly the attenuation coefficient was replaced by effective attenuation coefficient in scattering dominating turbid bio-tissue. The computation results of the modified method were compared with Monte Carlo simulation and showed the model provided reasonable predictions of heat source term distribution than past methods. Such a research is useful for explaining the physical characteristics of heat source in the heat transfer equation, establishing effective photo-thermal model, and providing theory contrast for related laser medicine experiments.

  6. Discriminating crude oil grades using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    El-Hussein, A.; Marzouk, A.; Harith, M. A.

    2015-11-01

    The analysis of crude oil using laser-based analytical techniques such as laser-induced breakdown spectroscopy (LIBS) has become of great interest to various specialists in different fields such as geology, petro-chemistry and environmental science. In this work, a detailed study is presented wherein the implementation of an efficient and simple LIBS technique to identify the elemental constituents of crude oil and to distinguish between different grades of petroleum crude oil is discussed. Laser-induced plasma (LIP) technique has been used in this work for direct measurements of atomic, ionic and molecular species in dry crude oil samples with API gravities ranging between 18 and 36. The technique was implemented using the first harmonic of a pulsed Nd-YAG laser source. Atomic and molecular emission bands were observed, consisting of characteristic spectral lines of atoms and diatomic molecular bands, namely from C, H, Si, Na, Ca, Mg, AL, Fe, Ti, Mo, C2 and CN. The intensities of high-resolution spectral lines for some atoms and molecules of elements such as Ca, Na, Fe, Mo, C2 and CN were evaluated at different wavelengths along the obtained spectra. The molecular bands and the elemental spectral lines were used to assess the possibility of adopting the LIBS technique in differentiating between crude oil samples with different American Petroleum Institute (API) gravity values. The results indicate the presence of a distinct correlation between the API gravity values of the various oil samples and the spectral line intensities of the elements and some molecular radical constituents. In addition, the possibility of identifying the API gravity values of unknown oil samples is also indicated.

  7. A handheld laser-induced fluorescence detector for multiple applications.

    PubMed

    Fang, Xiao-Xia; Li, Han-Yang; Fang, Pan; Pan, Jian-Zhang; Fang, Qun

    2016-04-01

    In this paper, we present a compact handheld laser-induced fluorescence (LIF) detector based on a 450 nm laser diode and quasi-confocal optical configuration with a total size of 9.1 × 6.2 × 4.1 cm(3). Since there are few reports on the use of 450 nm laser diode in LIF detection, especially in miniaturized LIF detector, we systematically investigated various optical arrangements suitable for the requirements of 450 nm laser diode and system miniaturization, including focusing lens, filter combination, and pinhole, as well as Raman effect of water at 450 nm excitation wavelength. As the result, the handheld LIF detector integrates the light source (450 nm laser diode), optical circuit module (including a 450 nm band-pass filter, a dichroic mirror, a collimating lens, a 525 nm band-pass filter, and a 1.0mm aperture), optical detector (miniaturized photomultiplier tube), as well as electronic module (including signal recording, processing and displaying units). This detector is capable of working independently with a cost of ca. $2000 for the whole instrument. The detection limit of the instrument for sodium fluorescein solution is 0.42 nM (S/N=3). The broad applicability of the present system was demonstrated in capillary electrophoresis separation of fluorescein isothiocyanate (FITC) labeled amino acids and in flow cytometry of tumor cells as an on-line LIF detector, as well as in droplet array chip analysis as a LIF scanner. We expect such a compact LIF detector could be applied in flow analysis systems as an on-line detector, and in field analysis and biosensor analysis as a portable universal LIF detector. PMID:26838391

  8. In Vitro Effect of Laser-Induced Hydrodynamics on Cancer Cells.

    PubMed

    Elagin, V V; Pavlikov, A I; Yusupov, V I; Shirmanova, M V; Zagaynova, E V; Bagratashvili, V N

    2015-11-01

    We studied the effect of laser-induced hydrodynamic on viability of Colo-26 murine colon carcinoma cells in vitro. Laser-induced hydrodynamics was generated by a laser (λ=1.56 μ, power 3 W, 5 min exposure); to this end, the fiber end was submersed into a buffer above the cell monolayer. It was found that laser-induced hydrodynamics destructed the monolayer at standoff distances of between the working end of the laser fiber to cell monolayer of 1 and 5 mm and triggers apoptotic and necrotic death in remaining cells at a distance of 4 mm from the emitter.

  9. Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

    SciTech Connect

    Huynh, T. T. D.; Petit, A.; Semmar, N.

    2015-11-09

    Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.

  10. Investigation of the early stages in laser-induced ignition by Schlieren photography and laser-induced fluorescence spectroscopy.

    PubMed

    Lackner, Maximilian; Charareh, S; Winter, F; Iskra, K; Rüdisser, D; Neger, T; Kopecek, H; Wintner, E

    2004-09-20

    Laser ignition has been discussed widely as a potentially superior ignition source for technical appliances such as internal combustion engines. Ignition strongly affects overall combustion, and its early stages in particular have strong implications on subsequent pollutant formation, flame quenching, and extinction. Our research here is devoted to the experimental investigation of the early stages of laser-induced ignition of CH4/air mixtures up to high pressures. Tests were performed in a 0.9-l combustion cell with initial pressures of up to 25 bar with stoichiometric to fuel-lean mixtures using a 5-ns 50-mJ 1064-nm Nd:YAG laser. Laserinduced fluorescence (LIF) was used to obtain two dimensionally resolved images of the OH radical distribution after the ignition event. These images were used to produce an animation of laser ignition and early flame kernel development. Schlieren photography was used to investigate the laserinduced shock wave, hot core gas, and developing flame ball. We extend existing knowledge to high-pressure regimes relevant for internal combustion engines.

  11. Investigation of the early stages in laser-induced ignition by Schlieren photography and laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lackner, Maximilian; Charareh, S.; Winter, F.; Iskra, K. F.; Rüdisser, D.; Neger, T.; Kopecek, H.; Wintner, E.

    2004-09-01

    Laser ignition has been discussed widely as a potentially superior ignition source for technical appliances such as internal combustion engines. Ignition strongly affects overall combustion, and its early stages in particular have strong implications on subsequent pollutant formation, flame quenching, and extinction. Our research here is devoted to the experimental investigation of the early stages of laser-induced ignition of CH4/air mixtures up to high pressures. Tests were performed in a 0.9-l combustion cell with initial pressures of up to 25 bar with stoichiometric to fuel-lean mixtures using a 5-ns 50-mJ 1064-nm Nd:YAG laser. Laserinduced fluorescence (LIF) was used to obtain two dimensionally resolved images of the OH radical distribution after the ignition event. These images were used to produce an animation of laser ignition and early flame kernel development. Schlieren photography was used to investigate the laserinduced shock wave, hot core gas, and developing flame ball. We extend existing knowledge to high-pressure regimes relevant for internal combustion engines.

  12. Laser induced mechanisms controlling the size distribution of metallic nanoparticles.

    PubMed

    Liu, Zeming; Vitrant, Guy; Lefkir, Yaya; Bakhti, Said; Destouches, Nathalie

    2016-09-21

    This paper describes a model to simulate changes in the size distribution of metallic nanoparticles (NPs) in TiO2 films upon continuous wave light excitation. Interrelated laser induced physical and chemical processes initiated directly by photon absorption or by plasmon induced thermal heating are considered. Namely the model takes into account the NP coalescence, Ostwald ripening, the reduction of silver ions and the oxidation of metallic NPs, competitive mechanisms that can lead to counter-intuitive behaviors depending on the exposure conditions. Theoretical predictions are compared successfully to the experimental results deduced from a thorough analysis of scanning transmission electron microscopy (STEM) pictures of Ag:TiO2 films processed with a scanning visible laser beam at different speeds. Ag:TiO2 systems are considered for many applications in solar energy conversion, photocatalysis or secured data printing. Numerical investigations of such a system provide a better understanding of light induced growth and shrinking processes and open up prospects for designing more efficient photocatalytic devices based on metal NP doped TiO2 or for improving the size homogeneity in self-organized metallic NP patterns, for instance. PMID:27539293

  13. [Neovascular glaucoma--etipathogeny and diagnosis].

    PubMed

    Călugăru, D; Călugăru, M

    2012-01-01

    Neovascular glaucoma is defined as an iris and/or anterior chamber angle neovascularization associated with increased intraocular presure. It is a secondary glaucoma most frequently determined by a severe retinal ischemia. The most common diseases responsible for the development of neovascular glaucoma are diabetic retinopathy, ischemic central retinal vein occlusion and ocular ischemic syndrome; the uncommon causes include ocular radiation, ocular tumors, uveitis and other miscellaneous conditions. Vascular endothelial growth factor is an important and probably predominant agent in the pathogenesis of both intraocular neovascularization and neovascular glaucoma. The evolution of clinical and histopathological changes from predisposing conditions to the occurrence of rubeosis iridis as well as neovacular glaucoma is divided into four grades that is prerubeotic, preglaucomatous, open-angle and angle closure glaucoma stages.

  14. Study on elucidation of bactericidal effects induced by laser beam irradiation Measurement of dynamic stress on laser irradiated surface

    NASA Astrophysics Data System (ADS)

    Furumoto, Tatsuaki; Kasai, Atsushi; Tachiya, Hiroshi; Hosokawa, Akira; Ueda, Takashi

    2010-09-01

    In dental treatment, many types of laser beams have been used for various surgical treatments, and the influences of laser beam irradiation on bactericidal effect have been investigated. However, most of the work has been performed by irradiating to an agar plate with the colony of bacteria, and very few studies have been reported on the physical mechanism of bactericidal effects induced by laser beam irradiation. This paper deals with the measurement of dynamic stress induced in extracted human enamel by irradiation with Nd:YAG laser beams. Laser beams can be delivered to the enamel surface through a quartz optical fiber. Dynamic stress induced in the specimen using elastic wave propagation in a cylindrical long bar made of aluminum alloy is measured. Laser induced stress intensity is evaluated from dynamic strain measured by small semiconductor strain gauges. Carbon powder and titanium dioxide powder were applied to the human enamel surface as absorbents. Additionally, the phenomenon of laser beam irradiation to the human enamel surface was observed with an ultrahigh speed video camera. Results showed that a plasma was generated on the enamel surface during laser beam irradiation, and the melted tissues were scattered in the vertical direction against the enamel surface with a mushroom-like wave. Averaged scattering velocity of the melted tissues was 25.2 m/s. Induced dynamic stress on the enamel surface increased with increasing laser energy in each absorbent. Induced dynamic stresses with titanium dioxide powder were superior to those with carbon powder. Induced dynamic stress was related to volume of prepared cavity, and induced stress for the removal of unit volume of human enamel was 0.03 Pa/mm 3.

  15. Confocal scanning laser ophthalmoscopic imaging resolution of secondary retinal effects induced by laser radiation

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Lund, David J.; Stuck, Bruce E.; Zuclich, Joseph A.; Elliot, Rowe; Schuschereba, Steven T.; Gagliano, Donald A.; Belkin, M.; Glickman, Randolph D.

    1996-02-01

    We have evaluated secondary laser induced retinal effects in non-human primates with a Rodenstock confocal scanning laser ophthalmoscope. A small eye animal model, the Garter snake, was employed to evaluate confocal numerical aperture effects in imaging laser retinal damage in small eyes vs. large eyes. Results demonstrate that the confocal image resolution in the Rhesus monkey eye is sufficient to differentiate deep retinal scar formation from retinal nerve fiber layer (NFL) damage and to estimate the depth of the NFL damage. The best comparison with histological depth was obtained for the snake retina, yielding a ratio close to 1:1 compared to 2:1 for the Rhesus. Resolution in the Garter snake allows imaging the photoreceptor matrix and therefore, evaluation of the interrelationship between the primary damage site (posterior retina), the photoreceptor matrix, and secondary sites in the anterior retina such as the NFL and the epiretinal vascular system. Alterations in both the retinal NFL and epiretinal blood flow rate were observed within several minutes post Argon laser exposure. Unique aspects of the snake eye such as high tissue transparency and inherently high contrast cellular structures, contribute to the confocal image quality. Such factors may be nearly comparable in primate eyes suggesting that depth of resolution can be improved by smaller confocal apertures and more sensitive signal processing techniques.

  16. Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.

    PubMed

    Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

    2013-11-19

    The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown.

  17. Neurodegeneration severity can be predicted from early microglia alterations monitored in vivo in a mouse model of chronic glaucoma

    PubMed Central

    Bosco, Alejandra; Romero, Cesar O.; Breen, Kevin T.; Chagovetz, Alexis A.; Steele, Michael R.; Ambati, Balamurali K.; Vetter, Monica L.

    2015-01-01

    ABSTRACT Microglia serve key homeostatic roles, and respond to neuronal perturbation and decline with a high spatiotemporal resolution. The course of all chronic CNS pathologies is thus paralleled by local microgliosis and microglia activation, which begin at early stages of the disease. However, the possibility of using live monitoring of microglia during early disease progression to predict the severity of neurodegeneration has not been explored. Because the retina allows live tracking of fluorescent microglia in their intact niche, here we investigated their early changes in relation to later optic nerve neurodegeneration. To achieve this, we used the DBA/2J mouse model of inherited glaucoma, which develops progressive retinal ganglion cell degeneration of variable severity during aging, and represents a useful model to study pathogenic mechanisms of retinal ganglion cell decline that are similar to those in human glaucoma. We imaged CX3CR1+/GFP microglial cells in vivo at ages ranging from 1 to 5 months by confocal scanning laser ophthalmoscopy (cSLO) and quantified cell density and morphological activation. We detected early microgliosis at the optic nerve head (ONH), where axonopathy first manifests, and could track attenuation of this microgliosis induced by minocycline. We also observed heterogeneous and dynamic patterns of early microglia activation in the retina. When the same animals were aged and analyzed for the severity of optic nerve pathology at 10 months of age, we found a strong correlation with the levels of ONH microgliosis at 3 to 4 months. Our findings indicate that live imaging and monitoring the time course and levels of early retinal microgliosis and microglia activation in glaucoma could serve as indicators of future neurodegeneration severity. PMID:25755083

  18. Laser-induced breakdown in large transparent water droplets.

    PubMed

    Chang, R K; Eickmans, J H; Hsieh, W F; Wood, C F; Zhang, J Z; Zheng, J B

    1988-06-15

    Recent experiments on the laser-induced breakdown (LIB) of large transparent liquid droplets are reviewed. A physical model of LIB processes is presented with the aim of integrating the following recent results: (1) the internal and near-field distributions for large transparent spheres; (2) the location of LIB initiation based on spatially resolved plasma emission spectroscopic techniques; (3) spatially resolved but time-averaged density of the plasma plumes and temperature of the atomic species within the plasma; (4) the plasma front propagation velocities inside and outside the droplet; and (5) the fate of the remaining superheated droplet and the expelled material.

  19. Interaction between jets during laser-induced forward transfer

    SciTech Connect

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.; Hennig, G.; Delaporte, P.

    2014-07-07

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  20. Laser-induced backward transfer of nanoimprinted polymer elements

    NASA Astrophysics Data System (ADS)

    Feinaeugle, Matthias; Heath, Daniel J.; Mills, Benjamin; Grant-Jacob, James A.; Mashanovich, Goran Z.; Eason, Robert W.

    2016-04-01

    Femtosecond laser-induced backward transfer of transparent photopolymers is demonstrated in the solid state, assisted by a digital micromirror spatial light modulator for producing shaped deposits. Through use of an absorbing silicon carrier substrate, we have been able to successfully transfer solid-phase material, with lateral dimensions as small as ~6 µm. In addition, a carrier of silicon incorporating a photonic waveguide relief structure enables the transfer of imprinted deposits that have been accomplished with surface features exactly complementing those present on the substrate, with an observed minimum feature size of 140 nm.