Diabetes-associated retinal nerve fiber damage evaluated with scanning laser polarimetry.
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Diabetes Mellitus, Type 2↗
Biomedical subjects
Neil T Choplin
Publications and source records attributed to Neil T Choplin.
Retinal nerve fiber layer measurements do not change after LASIK for high myopia as measured by scanning laser polarimetry with custom compensation.
PURPOSE: Scanning laser polarimetry (SLP) estimates retinal nerve fiber layer (RNFL) thickness through measurement of retardation of polarized light passing through the birefringent RNFL and cornea. A compensation method is incorporated to eliminate the anterior segment contribution to the total birefringence measured. LASIK is a technique that corrects myopia by ablating corneal tissue. This study evaluated RNFL measurements before and after LASIK as determined by SLP with a new custom compensation device set for the individual cornea before and after ablation. DESIGN: Interventional case series. PATIENTS AND METHODS: Patients underwent SLP measurements before and 30 days after LASIK for high myopia with customized compensation for anterior segment birefringence. Postoperative measurements were obtained with both the same compensation as was used preoperatively and with newly determined customized compensation. Standard RNFL parameters obtained before and after ablation with customized compensation were compared by use of paired Student's t tests with Bonferroni's correction for multiple comparisons. Postoperative measurements were also compared with those obtained preoperatively with the same corneal compensation measures as used preoperatively. MAIN OUTCOME MEASURES: Retinal nerve fiber layer parameters as determined by SLP before and after LASIK with 2 custom cornea compensator settings postoperatively. RESULTS: Fifty-seven eyes of 29 patients with myopia > -5.00 diopters underwent LASIK (average central ablation depth 101+/-11.3 mum). None of the 13 parameters showed statistically significant differences between preoperative and postoperative values with individually determined corneal compensation. When the preoperative corneal compensation was used postoperatively, 10 of 13 parameters were significantly changed. Comparison of the compensator settings before and after LASIK showed substantial differences in some individuals. On the average, there was a statistically significant change in the slow polarization axis of the cornea, with no statistically significant change in the magnitude of the birefringence, with some eyes showing increases and others decreases. The change in an individual cornea could not be predicted. CONCLUSIONS: Changes in RNFL measurements by SLP observed after LASIK in patients with high myopia are due to changes in corneal birefringence. These RNFL changes are not seen when customized compensation is applied for the cornea. Thus, LASIK does change the corneal birefringence but does not affect the RNFL.
Adult↗
A six-month randomized clinical trial comparing the intraocular pressure-lowering efficacy of bimatoprost and latanoprost in patients with ocular hypertension or glaucoma.
PURPOSE: To compare the intraocular pressure (IOP)-lowering efficacy and safety of topical bimatoprost 0.03% with latanoprost 0.005%. DESIGN: Multicenter, randomized, investigator-masked clinical trial. METHODS: After washout of glaucoma medications, ocular hypertension or glaucoma patients were randomly assigned to once-daily bimatoprost 0.03% (n = 133) or latanoprost 0.005% (n = 136) for 6 months. The primary outcome measure was mean change from baseline IOP (8 AM, 12 PM, 4 PM). Secondary measures included mean IOP, ophthalmologic examination, adverse events, and the percentage of patients reaching specific target IOPs. RESULTS: Mean change from baseline IOP was significantly greater for bimatoprost patients than for latanoprost patients at all measurements on each study visit; 1.5 mm Hg greater at 8 AM (P <.001), 2.2 mm Hg greater at 12 PM (P <.001), and 1.2 mm Hg greater at 4 PM (P =.004) at month 6. At the end of the study, the percentage of patients achieving a > or = 20% IOP decrease was 69% to 82% with bimatoprost and 50% to 62% with latanoprost (P < or = .003). In addition, the distribution of patients achieving target pressures in each range (< or = 13 to < or = 15 mm Hg, >15 to < or = 18 mm Hg, and > 18 mm Hg) showed that bimatoprost produced lower target pressures compared with latanoprost at all times measured (P < or = .026). Few patients were discontinued for adverse events (6 on bimatoprost; 5 on latanoprost). On ophthalmologic examination, conjunctival hyperemia (P <.001) and eyelash growth (P =.064) were more common in bimatoprost patients. CONCLUSIONS: Bimatoprost is more effective than latanoprost in lowering IOP. Both drugs were well tolerated, with few discontinuations for adverse events.
Adult↗
Effect of individualized compensation for anterior segment birefringence on retinal nerve fiber layer assessments as determined by scanning laser polarimetry.
PURPOSE: Scanning laser polarimetry estimates retinal nerve fiber layer (RNFL) thickness through measurement of retardation of a polarized laser light passing through the naturally birefringent RNFL and cornea. The commercial instrument, the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies, Inc., San Diego, CA), uses an anterior segment compensator of fixed magnitude and slow polarization axis to eliminate the contribution of the cornea to the total signal. Previous studies have shown up to 30% of patients are not adequately compensated by this method. The aim of this study was to determine the effect of individualized anterior segment compensation using a newly designed variable compensator on estimates of retinal nerve fiber layer thickness compared with those as determined with the fixed compensator in the commercial device. DESIGN: Comparative, observational case series. PARTICIPANTS: Twenty-eight eyes from 14 normal participants and 24 eyes from 12 patients with bilateral glaucoma. METHODS: Using information derived from a scan of the macula, a newly designed variable anterior segment compensator for the GDx was set to neutralize anterior segment birefringence. Normal participants and patients with glaucoma underwent RNFL measurements using the standard (fixed) compensator and the variable compensator. The results were compared using Hotelling's generalized means test and Bonferroni's adjustment for multiple comparisons. MAIN OUTCOME MEASURES: Standard GDx modulation and thickness parameters as determined with the fixed and variable compensators. RESULTS: All thickness values were statistically significantly lower as determined with the variable compensator, with no discernible differences in any of the modulation parameters. CONCLUSIONS: Individualized anterior segment compensation lowers the RNFL thickness values as determined by scanning laser polarimetry compared with those determined with the standard fixed compensator. This may narrow the normal range and increase the discriminating ability of scanning laser polarimetry between normal and disease. However, modulation is less affected, and the modulation parameters may thus prove more useful for distinguishing between normal and glaucoma.
Aged↗