Quantitative analysis of diabetic macular ischemia using optical coherence tomography

Abstract

Purpose: We described the optical coherence tomography (OCT) features of diabetic macular ischemia (DMI), and correlate these findings with visual acuity (VA).

Methods: Clinical and imaging data were collected from 100 patients with type 2 diabetes. Qualitative grading of DMI severity was determined according to criteria defined by the Early Treatment Diabetic Retinopathy Study. Quantitative analysis of foveal avascular zone (FAZ), and OCT images were performed using custom software.

Results: In all eyes, the outer retina was thicker in eyes with DMI (167.4 ± 18.5 vs. 150.4 ± 31.4 μm, P = 0.04). However, subanalysis of eyes "without macular edema" revealed the converse; outer retinal thinning in eyes with DMI (223.1 ± 31.2 vs. 244.9 ± 37.2 μm, P = 0.007). A thinner retinal nerve fiber layer also was observed to correlate with increasing FAZ size (r = -0.231, P = 0.03), which strengthened in eyes "without macular edema" (r = -0.62, P = 0.001). In the choroid, quantification of its sublayers revealed a thicker Haller's large vessel layer in the presence of DMI (144.3 ± 51.0 vs. 103.5 ± 39.4 μm, P = 0.01). In eyes with DMI, a thicker retina was correlated with worsening VA (r = 0.52, P = 0.001). However, when eyes with macular edema were excluded, a thinner retina was associated with poor VA (r = -0.37, P = 0.004).

Conclusions: In eyes with DMI, we observed thinning of the retinal nerve fiber layer, outer retina, and thickening of Haller's large vessel layer of the choroid. These parameters showed good correlation with VA and may serve as a useful tool for monitoring DMI in clinical practice or future clinical trials.

Keywords: diabetes mellitus; diabetic retinopathy; fluorescein angiography; ischemia; maculopathy; optical coherence tomography; visual acuity.