Foveal avascular zone changes in patients with diabetes, no retinopathy, and oscillatory potential delays

Abstract

Purpose : Optical coherence tomography angiography (OCT-A) can be used to capture changes in microvasculature in diabetic eyes before clinically diagnosable retinopathy. Previous studies have found foveal avascular zone (FAZ) enlargement and irregularity in patients with diabetes and no retinopathy compared to healthy controls. We have previously shown that delays in electroretinogram (ERG) oscillatory potential (OP) implicit times (IT) in patients with diabetes precede vascular pathology observed in fundus exams. Here, we evaluated microvascular changes using OCT-A in individuals with diabetes with and without OP delays.

Methods : OCT-A en face images (30x15°) from 29 patients with diabetes and without clinical diabetic retinopathy or other ocular conditions were acquired using OCT-A (Heidelberg SPECTRALIS HRA+OCTA). The eye with the greatest average OP IT was used for analysis of the FAZ. OCT-A metrics included FAZ circularity, size, and perimeter length in the superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Using a modified version of the Kanno-Saitama macro, en face scans were analyzed (ImageJ). ERGs were recorded with a handheld device (LKC RETeval) under dim flash conditions. Correlation analysis was performed with Pearson’s correlation coefficient.

Results : Eighteen eyes without OP delays and eleven eyes with OP delays were included in the study. FAZ circularity between groups with and without OP delays was not significantly different at any layer. Eyes with OP delays had significantly smaller FAZ areas in the ICP (0.20 +/- 0.09 mm²) compared to individuals with diabetes without OP delays (0.28 +/- 0.09 mm²; p < 0.05). FAZ perimeters in the ICP were also significantly smaller in diabetic eyes with OP delays (1.78 +/- 0.44 mm) than eyes without OP delays (2.13 +/- 0.41 mm; p < 0.05). There were no significant correlations between OP IT and FAZ metrics at any layer.

Conclusions : Our results suggest that FAZ microvasculature at the ICP may change in diabetic eyes with inner retinal dysfunction, as assessed by OP delays. These results support the hypothesis that early dysfunction in diabetic retinas may be accompanied by changes in retinal microvasculature, prior to detection of clinical diabetic retinopathy.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.