Atul Jain

Effect of Pulse Duration on Size and Character of the Lesion in Retinal Photocoagulation

OBJECTIVE To systematically evaluate the effects of laser beam size, power, and pulse duration of 1 to 100 milliseconds on the characteristics of ophthalmoscopically visible retinal coagulation lesions. METHODS A 532-nm Nd:YAG laser was used to irradiate 36 retinas in Dutch Belt rabbits with retinal beam sizes of 66, 132, and 330 mum. Lesions were clinically graded 1 minute after placement, their size measured by digital imaging, and their depth assessed histologically at different time points. RESULTS Retinal lesion size increased linearly with laser power and logarithmically with pulse duration. The width of the therapeutic window, defined by the ratio of the threshold power for producing a rupture to that of a mild coagulation, decreased with decreasing pulse durations. For 132- and 330-mum retinal beam sizes, the therapeutic window declined from 3.9 to 3.0 and 5.4 to 3.7, respectively, as pulse duration decreased from 100 to 20 ms. At pulse durations of 1 millisecond, the therapeutic window decreased to unity, at which point rupture and a mild lesion were equally likely to occur. CONCLUSIONS At shorter pulse durations, the width and axial extent of the retinal lesions are smaller and less dependent on variations in laser power than at longer durations. The width of the therapeutic window, a measure of relative safety, increases with the beam size. CLINICAL RELEVANCE Pulse durations of approximately 20 milliseconds represent an optimal compromise between the favorable impact of speed, higher spatial localization, and reduced collateral damage on one hand, and sufficient width of the therapeutic window (> 3) on the other.

Healing of Retinal Photocoagulation Lesions

PURPOSE To systematically assess the changes in retinal morphology during the healing of retinal photocoagulation lesions of various clinical grades. METHODS Rabbits were irradiated with a 532-nm Nd:YAG laser with a beam diameter of 330 microm at the retinal surface, a power of 175 mW, and pulse durations between 5 and 100 ms. Retinal lesions were clinically graded 1 minute after placement as invisible, barely visible, light, moderate, intense, very intense, and rupture and were assessed histologically at six time points from 1 hour to 4 months. RESULTS At all pulse durations, the width of the retinal lesions decreased over time. At clinical grades of light and more severe (pulse durations, 10-100 ms), retinal scarring stabilized at 1 month at approximately 35% of the initial lesion diameter. Lesions clinically categorized as barely visible and invisible (pulse durations of 7 and 5 ms) exhibited coagulation of the photoreceptor layer but did not result in permanent scarring. In these lesions, photoreceptors completely filled in the damaged areas by 4 months. CONCLUSIONS The decreasing width of the retinal damage zone suggests that photoreceptors migrating from unaffected areas fill in the gap in the photoreceptor layer. Laser photocoagulation parameters can be specified to avoid not only the inner retinal damage, but also permanent disorganization and scarring in the photoreceptor layer. These data may facilitate studies to determine those aspects of laser treatment necessary for beneficial clinical response and those that result in extraneous retinal damage.

Surveillance for potential adverse events associated with the use of intravitreal bevacizumab for retinal and choroidal vascular disease.

Purpose: To systematically study potential adverse events associated with the use of intraocular bevacizumab at a single medical center. Methods: Retrospective study of all consecutive patients receiving intraocular bevacizumab injections at the Stanford University Department of Ophthalmology between November 15, 2005 and July 14, 2006. Bevacizumab was given for exudative age-related macular degeneration, retinal vascular occlusion, diabetic macular edema, neovascular glaucoma, and five other indications. Results: We analyzed medical records of 186 subjects (203 eyes) who received a total of 578 injections of 1.25 mg of bevacizumab. The average follow-up was approximately 6 months. Five eyes with exudative age-related macular degeneration developed retinal pigment epithelial (RPE) tears, all with preexisting RPE detachments. These five eyes represented 2.9% of all age-related macular degeneration eyes treated and 7% of the age-related macular degeneration eyes with preexisting RPE detachments at initiation of treatment. Other adverse events were rare and included retinal ischemia, subretinal hemorrhage, vitreous hemorrhage, ocular irritation or pain, worsened hypertension, and headache. No death or thromboembolic events were observed. Conclusion: Intraocular bevacizumab appears to be well tolerated for the treatment of a variety of retinal and choroidal vascular diseases. RPE tears may occur when treating choroidal neovascularization, particularly in patients with preexisting RPE detachment.

Prospective Long-term Evaluation of the Efficacy, Safety, and Stability of the Phakic Intraocular Lens for High Myopia

OBJECTIVE To evaluate the safety, efficacy, predictability, and long-term stability of the Artisan Phakic Intraocular Lens (Ophtec BV, Groningen, the Netherlands) for the correction of high myopia. METHODS Prospective analysis of 26 eyes from 15 patients who underwent placement of the Artisan lens for the correction of high and extreme myopia. The mean (SD) preoperative spherical equivalent was - 12.30 (2.69) diopters (D) (range, - 17.25 to - 8.25 D). RESULTS At 5 years, the mean (SD) manifest refraction was - 0.37 (0.69) D, with 95% of eyes within 1 D of attempted correction and 74% of eyes within 0.5 D of the attempted correction. Ninety-five percent of eyes achieved an uncorrected visual acuity of 20/40 or better and 74% achieved an uncorrected visual acuity of 20/20 or better. No eyes experienced a loss of 1 or more lines of best-corrected visual acuity. Sixteen percent of eyes gained 2 or more lines of best-corrected visual acuity. From preoperative measurements, the mean endothelial cell density decreased by 14.05% at 5 years postoperatively. CONCLUSIONS Placement of the Artisan lens is predictable, stable, and effective at reducing high and extreme myopia 5 years after implantation. The rate of endothelial cell loss was significantly higher than has been reported in previous studies.

Mucosa-associated lymphoid tissue lymphoma with intraocular involvement.

Purpose: To report the clinicopathologic features of a patient with mucosa-associated lymphoid tissue (MALT) lymphoma of the conjunctiva and associated intraocular involvement. Methods: This study is a retrospective clinicopathologic correlative case report summarizing the clinical, radiologic, and histopathologic findings of a patient with conjunctival MALT lymphoma and associated intraocular involvement. Results: Ophthalmic examination and fluorescein angiography demonstrated progressive conjunctival infiltration bilaterally, marked uveal effusions in the left eye, and cellular white infiltrates of the choroid in the right eye. MRI of the orbit revealed a diffusely infiltrating intra- and extraocular lesion extending around the globe and optic nerve in the left eye without evidence of intracranial extension. Conjunctival biopsy showed low-grade tumor cells, consistent with the diagnosis of MALT lymphoma. The patient was successfully treated with external beam radiation with marked clinical improvement. Conclusion: Conjunctival MALT lymphomas, typically indolent and localized tumors, may extend into the orbit and invade local tissues such as the choroid with devastating consequences. A conjunctival biopsy can provide an easy diagnosis of this treatable entity.

Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP): 12-month experience with telemedicine screening

Background/aims: To report the 1-year experience of the Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP) telemedicine initiative. Methods: Forty-two consecutively enrolled infants who met ROP examination criteria were screened between 1 December 2005 through 30 November 2006 with the RetCam II and evaluated by the SUNDROP reading centre at Stanford University. Nurses obtained five images in each eye. All patients also received a dilated examination by the author within 1 week of discharge from the hospital. Outcomes included referral-warranted disease, need for treatment and anatomical outcomes. Referral-warranted disease was defined as any Early Treatment Retinopathy of Prematurity (ROP) Disease Type 2 or greater, or any plus disease. A retrospective analysis of 84 eyes, 131 unique examinations and 1315 unique images from the SUNDROP archival data is reported here. Results: In the initial 12-month period, the SUNDROP telemedicine screening initiative had not missed any referral warranted ROP. Calculated sensitivity and specificity was 100% and 95%, respectively. No patient progressed to retinal detachment or other adverse outcomes. Conclusions: The SUNDROP telemedicine screening initiative for ROP has proven to have a high degree of sensitivity and specificity for identification of referral warranted disease. These results indicate that telemedicine may improve accessibility of ROP screening.

Selective retinal therapy with microsecond exposures using a continuous line scanning laser.

Purpose: To evaluate the safety, selectivity, and healing of retinal lesions created using a continuous line scanning laser. Methods: A 532-nm Nd:YAG laser (PASCAL) with retinal beam diameters of 40 μm and 66 μm was applied to 60 eyes of 30 Dutch-belted rabbits. Retinal exposure duration varied from 15 μs to 60 μs. Lesions were acutely assessed by ophthalmoscopy and fluorescein angiography. Retinal pigment epithelial (RPE) flatmounts were evaluated with live-dead fluorescent assay. Histological analysis was performed at 7 time points from 1 hour to 2 months. Results: The ratios of the threshold of rupture and of ophthalmoscopic visibility to fluorescein angiography visibility (measures of safety and selectivity) increased with decreasing duration and beam diameter. Fluorescein angiography and live-dead fluorescent assay yielded similar thresholds of RPE damage. Above the ophthalmoscopic visibility threshold, histology showed focal RPE damage and photoreceptor loss at 1 day, without inner retinal effects. By 1 week, photoreceptor and RPE continuity was restored. By 1 month, photoreceptors appeared normal. Conclusion: Retinal therapy with a fast scanning continuous laser achieves selective targeting of the RPE and, at higher power, of the photoreceptors without permanent scarring or inner retinal damage. Continuous scanning laser can treat large retinal areas within standard eye fixation time.

Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP): 24-month experience with telemedicine screening

Purpose:  To report the 24‐month experience of the Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP) telemedicine initiative.

Long-term follow-up of hyperopic laser in situ keratomileusis correction using the Star S2 excimer laser

PURPOSE: To prospectively evaluate the safety, efficacy, predictability, and long‐term stability of hyperopic laser in situ keratomileusis (LASIK) using the Star S2 excimer laser (Visx). SETTING: Department of Ophthalmology, Stanford University School of Medicine, Stanford, California, USA. METHODS: This study evaluated 41 eyes of 27 patients who had LASIK for the correction of spherical hyperopia. Patients were divided into 3 groups based on preoperative cycloplegic refraction: low hyperopia (less than +2.00 diopters [D]), medium hyperopia (+2.00 to +4.00 D), and high hyperopia (more than +4.00 D). RESULTS: In all eyes, the mean preoperative spherical equivalent (SE) was +2.53 D (range +0.75 to +5.25 D) and the mean attempted SE was +2.58 D (range +0.75 to +5.25 D). At the last visit (mean 5.29 years), the mean SE was +0.44 D ± 0.69 (SD) in the low hyperopia group, +0.58 ± 0.56 D in the medium hyperopia group, and +0.59 ± 1.18 D in the high hyperopia group. The percentage of eyes within ±1.00 D of emmetropia was 82.4%, 75.0%, and 66.7%, respectively (68.9% overall). The uncorrected visual acuity was 20/40 or better in 100% of eyes in the low hyperopia group, 91.7% in the medium hyperopia group, and 66.7% in the high hyperopia group (87.8% overall). The hyperopic shift between 1 year and the last visit was +0.18 D, +0.30 D, and +0.55 D, respectively (+0.40 D overall; range −1.25 to +2.63 D). CONCLUSIONS: Hyperopic LASIK using the Star S2 excimer laser was safe, effective, and predictable for hyperopia up to +4.10 D (mean of high group). A mild regression of the refractive effect was seen over the 5‐year follow‐up.

Resolution of Persistent Exudative Retinal Detachment in a Case of Sturge-Weber Syndrome with Anti-VEGF Administration

Purpose: Report the resolution of a persistent exudative retinal detachment in a patient with Sturge-Weber syndrome following intravitreal pegaptanib injection. Design: Case report. Methods: A 13-year-old male with Sturge-Weber syndrome presented with a choroidal hemangioma associated with an exudative retinal detachment that failed to resolve 6 months after external beam radiation therapy. Results: A single intravitreal pegaptanib injection resulted in 50% resolution of the detachment within 1 week and complete resolution within a month. Despite anatomic success, vision remained poor. Conclusions: VEGF likely plays a role in the pathogenesis of Sturge-Weber choroidal hemangioma-associated exudative retinal detachment and offers potential treatment.