Researchers from Japan have determined that changes in the retina’s thickness were also reflected in its perfusion status; thus, retinal thickness maps could possibly provide clues about retinal circulation. Swept-source OCT-A analysis of eyes with proliferative diabetic retinopathy (PDR) revealed the inner retina was thinned at large areas of nonperfusion and local retinal thickening with smooth shapes corresponds with capillary abnormalities, while local retinal thickening with irregular shapes corresponded with neovascularization.

The study reviewed medical records of 70 eyes from 55 patients with diabetes. The researchers measured retinal layer thickness in nonperfused areas larger than two optic disc area, areas of sparse capillaries and perfused areas in eyes. The inner retinal thickness in nonperfused areas was significantly thinner than the inner retinal thicknesses in sparse capillary areas and perfused areas in both DR and non-DR eyes. Of these remaining groups, the inner retinal thickness in perfused areas in non-DR eyes and sparse capillary areas was significantly thinner than that in perfused areas in DR eyes. There were capillary abnormalities, such as capillary dropout and microaneurysms, at sites of local thickening with smooth shapes and gentle borders.

The researchers also found neovascularization at sites of local thickening with irregular shapes and unnatural clear borders in the extramacular area. A distribution analysis of the extramacular areas revealed that nonperfused areas overlapped with areas of severe retinal thinning in all locations.

“In circumstances where both OCT-A and fluorescein angiography are difficult, analysis of retinal thickness map can provide a clue to speculate the functioning of retinal circulation, although the retinal thickness map needs to be carefully interpreted along with B-scans,” the study authors conclude in their paper. “Advances in SS-OCT technology continue to progress, so the analysis of retinal layer thickness in the periphery should soon be possible.”

Ito H, Ito Y, Kataoka, K, et al. Association between retinal layer thickness and perfusion status in extramacular areas in diabetic retinopathy. Am J Ophthalmol. March 26, 2020. [Epub ahead of print].