Choroidal And Retinal Layer-By-Layer Analysis In Intermediate AMD Patients Using Manually-Segmented SD-OCT High Resolution B-Scans

Abstract

Purpose: To study the retinal and choroidal structure in age-related macular degeneration (AMD) patients with bilateral large drusen and pigment changes (intermediate AMD [iAMD]) analyzing SD-OCT high resolution (HR) B-scans

Methods: 21 eyes of 42 patients with iAMD, mean age 77.90±8.60 years, 11F and 10M, were studied. 19 eyes randomly selected in 38 healthy, age-matched, subjects were used as control eyes (CEs).<br /> All subjects had ametropia < 3D and underwent clinical examination including visual acuity evaluation using ETDRS chart and slit-lamp biomicroscopy with +90 D lens. The macula was studied with a SD-OCT Cirrus 5000 (Carl Zeiss Meditec, Inc) using a HR 6 mm horizontal B-scan (EDI HD5 line raster merged in a single scan), crossing the center of the fovea. The B-scan was divided in the middle of the fovea and the nasal and temporal scans were analyzed separately; total retina (TR) from inner limiting membrane to Bruch’s membrane, subretinal layers outer nuclear (ONL), inner nuclear (INL), ganglion cells (GCL) and choroid (Ch) were segmented using the software ImageJ ver.1.48v. Data underwent to indipendent 2-sample unequal variance t-test to evaluate difference between groups; a level of P<0,05 was accepted as statistically significant

Results: No significant differences were found when nasal and temporal ONL, INL and GCL thickness were compared in iAMD eyes vs CEs (0.379±0,005 vs 0.382±0.007 mm², P=0.70; 0.370±0,007 vs 0.366±0.006 mm², P=0.63; 0.153±0.004 vs 0.158±0.004 mm², P=0.37, 0.135±0.003 vs 0.143±0.004 mm², P=0.09; 0.226±0.005 vs 0.218±0.003 mm², P=0.21, 0.218±0.004 vs 0.218±0.004 mm², P=0.93; respectively). Significant differences were found between Ch and TR thickness (0.855±0.062 vs 0.680±0.054 mm², P=0.04; 0.901±0.040 vs 0.727±0.053 mm², P=0.01; 0.918±0.015 vs 0.984±0.029 mm², P=0.05; 0.814±0.008 vs 0.915±0.041 mm², P=0.02; respectively)

Conclusions: Data from this study show that SD-OCT HR B-scans analysis with proper software allows a reliable retinal and choroidal segmentation. We found a significant choroidal and total retinal thinning in iAMD eyes, as also demonstrated by other studies; however, it is interesting to highlight that in this study ONL, INL and GCL thickness differences between iAMD eyes and CEs were not significant. These findings could support the hypothesis that the choroid could play major role in the pathogenesis of iAMD