Scanning Laser Polarimetric Analysis of Retinal Nerve Fiber Layer Thickness in Turkish Patients with Glaucoma and Ocular Hypertension

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Abstract
Purpose: To assess the thickness of the retinal nerve fiber layer (RNFL) in patients with different stages of glaucoma, in comparison with ocular hypertensive (OHT) and healthy subjects in a Turkish population. Methods: Scanning laser polarimetry was done with a GDx Nerve Fiber Analyzer (NFA, GDx version, 1.0.08) on 270 eyes with glaucoma, 52 OHT eyes, and 81 normal eyes. The eyes were classified as having early (146 eyes), moderate (66 eyes) and severe (58 eyes) glaucoma based on the Humphrey Visual Field indices. We compared 14 NFA parameters by analysis of variance (ANOVA) and Scheffe multiple comparison analysis. Receiver operator characteristic curves (ROC) and Fisher linear discriminant analysis (LDF) were used to measure the sensitivity and specificity of the NFA parameters. Results: Except for symmetry, all NFA parameters showed significant differences between the groups (p<0.05). The eyes with glaucoma had significantly thinner RNFL than healthy eyes (p<0.01). The RNFL retardation measurements of OHT eyes were lower than controls, but higher than the early glaucoma group. The sensitivity and specificity of the GDx System were 87% and 72.8%, respectively. Applying LDF, the group with the highest sensitivity and specificity (85.9% and 74.1%) was determined as inferior ratio, superior/nasal ratio, superior maximum and the Number. Conclusions: Assessment of RNFL thickness with scanning laser polarimetry can distinguish glaucoma, OHT and normal subjects with relatively high sensitivity and specificity.