Optical coherence tomography and glaucoma progression: A region of interest approach is better than average retinal nerve fiber layer thickness

Abstract

Purpose : To determine whether retinal nerve fiber layer (RNFL) change in a region of interest (ROI) is a better measure of glaucoma progression than the change in average circumpapillary (cp) RNFL thickness, optical coherence tomography (OCT) scans were obtained on patients with mild glaucoma and both methods were compared.

Methods : Frequency domain OCT disc cube scans (3D-OCT2000, Topcon) were obtained from 71 eyes of 71 patients with or suspected early glaucoma, normal IOP, and at least 2 visits. All eyes had suspicious discs and 24-2 mean deviations better than -6 dB. Eleven eyes were excluded due to poor scan quality. For the remaining 60 eyes (age: 61.7 + 12.7 years), the last scan was an average of 3.2 + 1.8 yrs after the first. En-face images of the scans were aligned based on the blood vessels; circumpapillary images were derived for an annulus 100 µm in width centered on the optic disc; RNFL thickness plots were generated.[1] An ROI was defined as the portion of these plots within the temporal half of the disc that extended below the 1% confidence interval for 5° or more. The average cpRNFL thickness and ROI measurements were calculated for each eye on each visit and for repeat scans on the same visit from the same eyes. Additionally, 42 of the 71 eyes had repeat 24-2 visual fields, separated by 3.0 ±1.7 yrs on average.

Results : 26 of the 60 eyes had a total of 33 ROIs; 29 were in the central ±8°. The between-visit ROI change (median: 4.9 ^o; Q1=1.03 ^o, Q3=10.5^o) was significantly greater (p<0.00001) than the within-visit ROI change (median: 0^o; Q1= -1.7 ^o, Q3=1.7 ^o). In comparison, the between-visit average cpRNFL change (median: -0.7 µm; Q1= -2.7 µm, Q3=2.7 µm) was not significantly different (p=0.33) than the within-visit RNFL change (median: 0 µm; Q1= -1.6 µm, Q3=1.4 µm). Additionally, there was no relationship between ROI change and average cpRNFL change (r² = 0.003); the time between visits and the change in ROI width (r² = 0.04); or the RNFL thickness (r² = 0.17, p=0.17). The change in mean deviation or pattern standard deviation on the visual fields between visits for the early glaucoma subjects was not statistically significant.

Conclusions : In this population, cpRNFL thinning in a ROI is a better measure of progression than is average cpRNFL thickness. 1. Hood et al, JAMA Ophthal, 2015

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.