Background: Age-related macular degeneration (AMD) is one of the leading causes of blindness with loss of retinal layers over long term. We aim to evaluate these changes in eyes with progressive non-exudative AMD with geographic atrophy (GA).
Methods: This retrospective study included patients with GA with a minimum of 4 years follow up. Retinal layers on spectral domain optical coherence tomography (SD-OCT) were segmented based on their reflectivity patterns using validated semi-automated segmentation algorithm. The thickness of the segmented retinal layers was measured. Horizontal length of GA at baseline and last follow-up were also measured. Regression analysis was performed to correlate changes in RPE layer thickness with other retinal layers and the length of GA on OCT.
Results: A total of 351-line scans including 17 foveal scans showing presence of GA at final visit that is, a total of 2457 retinal layer bands were analyzed. Outer nuclear layer (ONL) (p = 0.02), outer segment layers (OSL) (p = 0.01), and retinal pigment epithelium (RPE) (p = 0.01) showed a statistically significant variation between baseline and final visit. Regression analysis showed the change in ONL (r = 0.72; p = 0.01) and OSL (r = 0.93, p < 0.01) correlated significantly with change in RPE thickness whereas rest of the layers failed to show significant correlation.
Conclusion: Outer retinal layers (ONL and OSL) show more significant and widespread changes in retinal thickness and correlated most significantly with RPE thickness changes in eyes with GA due to AMD. Assessment of various retinal layer bands can be used as surrogate quantitative parameters to study eyes with GA.
Keywords: Retinal thickness assessment; geographic atrophy; long-term retinal thickness changes; progressive retinal atrophy.