Topographic measurement of the sub-retinal pigment epithelium space in normal aging and age-related macular degeneration using volumetric high-resolution OCT

Abstract

Purpose : Micrometer scale changes in the hyporeflective band/split within the retinal pigment epithelium basal lamina (RPE-BL) – Bruch’s membrane (BrM) complex associated with aging and age-related macular degeneration (AMD) are topographically measured using high-resolution spectral domain-OCT (SD-OCT) and neural network segmentation.

Methods : A total of 90 normal eyes from 76 subjects (23-90 yrs) and 53 nonexudative (dry) AMD eyes from 47 patients (62-91 yrs) were enrolled in a prospective cross-sectional study. Isotropic volume raster scan protocols over 6 mm × 6mm field-of-view (500 × 500 A-scans) were acquired using a high-resolution SD-OCT prototype instrument with an axial resolution of 2.7 µm. Six consecutive OCT volumes were acquired, then computationally motion corrected and fused in 3D to improve feature visibility. A boundary regression neural network, Depth-Map Regression Network, was developed to measure the hyporeflective band vi thickness within the RPE-BL-BrM. A 6 mm diameter Early Treatment Diabetes Retinopathy Study (ETDRS) grid was utilized to evaluate the subfield dependence.

Results : The topographic thickness (µm) map of the hyporeflective band vi exhibits a radially symmetric pattern (Figure). In normal eyes, age-associated changes occur at the inner ring subfield (p<0.05). Hyporeflective band thickness decreases with normal aging, but significantly increases in AMD eyes at 0 – 2.1 mm foveal eccentricity (p<0.05), with stronger statistical power at <1.5 mm (p<0.0002). The inner ring subfield is the most sensitive location to detect age- and AMD-associated structural changes in the RPE-BL-BrM. AMD eyes with subretinal drusenoid deposits (SDDs) show a significantly thicker hyporeflective band, hypothesized to be from basal laminar deposit (BLamD), at 0.5 – 3 mm foveal eccentricity (p<0.001) than AMD eyes without SDDs.

Conclusions : Age- and AMD-associated hyporeflective band changes are more pronounced in the inner ETDRS subfield compared to the outer subfield. The hyporeflective band may be quantifiable biomarker which can facilitate clinical studies investigating the earliest structural-functional changes associated with disease pathogenesis and progression.

This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.

 

Figure A, Fused B-scan. COST=cone outer segment tip; ROST=rod outer segment tip. B-D, Flattened B-scan, zoomed in layer segmentations, and topographic thickness map.