Retinal Nerve Fiber Layer Thickness Correlates Well with Glaucoma Severity in African Americans with Primary Open Angle Glaucoma

Abstract

Purpose : Primary open-angle glaucoma (POAG) presents earlier and progresses faster in individuals of African Americans (AA) descent compared to Caucasians. The correlation between optic nerve optical coherence tomography (OCT) and glaucoma severity has not been fully elucidated in an exclusively AA population. In a retrospective cross-sectional study, we evaluated the association between glaucoma severity and retinal nerve fiber layer (RNFL) thickness in POAG cases.

Methods : 1236 eyes of 456 female and 276 male POAG cases (Mean±SD age=70±11yrs) diagnosed by fellowship-trained glaucoma specialists were included. Data was collected within a year of enrollment including: best corrected visual acuity (BCVA), average intraocular pressure (IOP), maximum IOP (IOP_max), central corneal thickness, cup-to-disc ratio (CDR), RNFL thickness on OCT, VF mean deviation (MD) and pattern standard deviation (PSD). Glaucoma severity was assigned to each eye using the Enhanced Glaucoma Staging System (GSS2) criteria. Associations were established using Pearson’s correlation coefficient (r) and linear regression that accounted for inter-eye correlation by generalized estimating equations.

Results : BCVA and IOP_max were significantly correlated with RNFL and GSS2 stage (p<0.001; Table 1). CDR, MD, and PSD were moderately correlated with RNFL (r=-0.54, 0.51, and -0.46; Table 1). RNFL thickness decreased linearly with increased GSS2 stage from 86µm in stage 0 to 63um in stage 5 (r=-0.51; Figure 1). RNFL thickness in superior and inferior quadrants were moderately correlated with GSS2 (r=-0.49 and -0.55), while correlations in the nasal and temporal quadrants were mild (r=-0.24 and -0.18; Figure 1a). RNFL thickness in each clock hour except 3 and 9 (nasal and temporal) correlated with GSS2 stage, with the strongest correlation for clock hours 6 and 7 (r=-0.49 and -0.50; Figure 1a).

Conclusions : In AA patient with POAG, RNFL thickness decreased linearly with increased glaucoma severity. RNFL thinning preceded VF changes in line with the “ISNT” rule. The results of this study may ultimately inform OCT-based screening and management of POAG in AA patients.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Correlations of clinical measures with RNFL and GSS2 stage.

 

Figure 1. a) Association between GSS2 stage and RNFL thickness: averaged and regional. b) GSS2 stage, derived from MD and PSD, correlates linearly with average RNFL.