Detection of progressive retinal nerve fiber layer thickness loss with optical coherence tomography using 4 criteria for functional progression

Abstract

Purpose: To compare the rates of retinal nerve fiber layer (RNFL) thickness loss using optical coherence tomography (OCT) in progressing versus nonprogressing eyes using 4 methods to define functional progression.

Methods: Normal and glaucomatous eyes with ≥3 years of follow up were prospectively enrolled. Standard automated perimetry (Swedish Interactive Threshold Algorithm Standard 24-2) and OCT (Stratus OCT, Carl Zeiss Meditec, Dublin, CA) imaging were performed every 6 months in glaucomatous eyes. OCT imaging was performed annually in normal eyes. Functional progression was determined using early manifest glaucoma trial criterion, visual field index (VFI), Progressor software, and the 3-omitting method.

Results: Seventy-six eyes (46 glaucoma and 30 normal) of 38 patients were enrolled with a mean follow-up of 43.9 ± 5.02 months (range: 36 to 48 mo). Eleven eyes progressed using Progressor criterion, 5 eyes using VFI, 2 eyes using the 3-omitting method, and 2 eyes using Early Manifest Glaucoma Trial criterion. The annual rate of average RNFL loss (μm/y) was significantly greater (P<0.05) in progressing versus nonprogressing eyes using Progressor (-1.0 ± 1.3 vs. 0.02 ± 1.6), VFI (-2.1 ± 1.1 vs. -0.002 ± 1.4), and the 3-omitting method (-2.2 ± 0.2 vs. -0.1 ± 1.5). Mean rate (μm/y) of average and superior RNFL thickness change was similar (P>0.05) in nonprogressing glaucomatous eyes compared with normal eyes. Using linear mixed-effect models, mean (P<0.001) and peak (P=0.01) intraocular pressure were significantly associated with rate of average RNFL atrophy in glaucomatous eyes.

Conclusions: Despite differences in criteria used to judge functional progression, eyes with standard automated perimetry progression have significantly greater rates of RNFL loss measured using OCT compared with nonprogressing eyes.

Figure 1

Criteria used for judgement of visual field progression. Guided Progression Analysis (GPA, left) identifies Likely Progression when a significant change in sensitivity is detected in ≥ 3 points and repeated in the same points (black triangles), on 3 consecutive follow-up tests. Progressor™ (center) identifies progression (red square) as a test point with significant (p < 0.01) sensitivity loss > 1 dB loss per year (non-edge points) or > 2 dB loss per year (edge points). A significant (p < 0.05) decline in the slope of the Visual Field Index (VFI, right) is defined as progression.

Figure 2

Scatterplot demonstrating relationship between the change of average retinal nerve fiber layer thickness (RNFLT) and mean visual field slope using Progressor™ among glaucomatous eyes (n = 46). The rate of RNFLT change (µm/year) was significantly (p < 0.001) correlated with the rate of visual field change (dB/year).