Correlation of Average RNFL Thickness Using the STRATUS OCT with the Perimetric Staging of Glaucoma

Objective: To determine the correlation between average peripapillary retinal nerve fiber layer (RNFL) thickness measured with time domain optical coherence tomography (TD-OCT) in normal and glaucoma eyes. Methods: This was a cross-sectional study of 281 eyes randomly selected from a previous study. Assessment of glaucomatous damage was done by glaucoma specialists who based their diagnosis on the visual field tests and optic disc photos, independent of OCT results. Eyes were classified into the following groups: normal, mild, moderate, or severe glaucoma. Severity of glaucoma was based on visual field abnormalities following a modified Hodapp-Anderson-Parish criteria for staging. Average RNFL thickness of normal and glaucoma subgroups, as measured with STRATUS–OCT, were analyzed using single ANOVA test. Association between average RNFL thickness and severity of glaucomatous visual field loss was evaluated using the Pearson’s correlation coefficient analysis. Results: 183 eyes had no glaucoma; 27 had mild, 32 had moderate, and 39 had severe glaucoma. Mean average peripapillary RNFL thickness (μm) in the normal, mild, moderate, and severe glaucoma groups were 98.05(±13.46), 76.27(±11.79), 76.42(±16.01), and 56.17(±14.92) respectively. Significant differences were seen in the average RNFL thickness among the groups (P<0.05), except in eyes with mild to moderate glaucoma. A moderately strong correlation of -0.57 (P<0.05) was observed between average RNFL thickness and the stage of glaucoma. Conclusion: TD-OCT showed moderately strong correlation between the average RNFL thickness and perimetric stages of glaucoma. Average RNFL thickness is a good parameter to discriminate normal from glaucoma eyes.