High-Resolution Blood Flow Imaging for Mild Non-Proliferative Diabetic Retinopathy by Adaptive Optics Scanning Laser Ophthalmoscopy

Abstract

Purpose: : To determine pathologic changes in the blood flow in eyes with mild nonproliferative diabetic retinopathy (NPDR) by using high-resolution images obtained by adaptive optics scanning laser ophthalmoscopy (AO-SLO).

Methods: : Six eyes of six patients with mild NPDR and 20 normal eyes of 20 volunteers were examined. All the subjects underwent a complete ophthalmologic examination, spectral-domain optical coherence tomography, and imaging with an original prototype of the AO-SLO system fabricated using liquid crystal-on-silicon technology. The AO-SLO system has a transverse resolution of 3 µm and can be used to observe retinal pathology at the cellular level,including direct visualization of the cone photoreceptors and the flow of white blood cells. Fluorescein angiography (FA) was performed in all patients with mild NPDR to compare the pathologic changes observed on AO-SLO with the FA findings.

Results: : In the cases of normal eyes, AO-SLO images showed a regular blood flow pattern. In the cases of eyes with mild NPDR, many highly reflective spots (about 10µm diameter) were seen on the inner walls of vessels on AO-SLO images, even in areas where FA showed no abnormalities; this may indicate the adhesion of leukocytes to the inner wall of the retinal vessels or leukocyte entrapment in retinal microcirculation. In some eyes, several bumps were observed in the blood flow images on AO-SLO, and FA showed the presence of microaneurysms in these areas. These bumps may indicate leukocyte entrapment in microaneurysms. These findings were not observed in normal eyes.

Conclusions: : AO-SLO images showed abnormal blood flow patterns in eyes with mild NPDR. These abnormalities may indicate the entrapment or adhesion of leukocytes in the retinal vessels; these findings have been shown to be involved in the pathogenesis of various pathogenic conditions, including diabetes, only in animal models. Thus, AO-SLO may be a useful modality to study the abnormalities in microcirculation that are associated with the pathogenesis of diabetic retinopathy.

Keywords: imaging/image analysis: clinical • diabetic retinopathy