Abstract
Purpose :
Alterations in retinal oxygen metabolism and microvascular perfusion have been described as signs indicative of the development of diabetic retinopathy. However, it is so far unknown which areas or quadrants of the retina are affected first. The purpose of this study was to investigate if early changes in microvascular alteration follow a distinct regional pattern of distribution.
Methods :
Type II diabetic patients without diabetic retinopathy were imaged consecutively with 2 devices and one eye in each patient was chosen randomly for analysis. Fundus camera-based, dual-wavelength oximetry was performed to measure retinal oxygen saturation in major peripapillary vessels (defined by a diameter ≥ 93 μm) supplying the four retinal quadrants. Inner retinal peripapillary microvascular flow was determined by optical coherence tomography angiography (OCTA) using a prototype system with a swept-source laser at a central wavelength of 1050 nm, a post-processing sweep rate of 400 kHz and a 16 degrees field of view. After manual segmentation and exclusion of vessels with a diameter ≥ 93 μm, the flow index, defined as the mean flow signal intensity ranging from 0 to 1, was calculated in the remaining microvascular bed.
Results :
Sixteen eyes of 16 patients (59±11 years, 5 female) were included in this study. Retinal oxygen saturation was 97.25±5.39 % in arterioles (128.88±10.72 μm diameter) and 61.58±7.95 % in venules (156.96±14.14 μm diameter), resulting in a total oxygen extraction of 35.67±5.63 %. In general, the saturation was higher nasally than temporally showing a decreasing pattern from the upper nasal through the lower nasal, upper temporal and lower temporal quadrant in arterioles and venules. In contrast, DOCTA peripapillary flux tended to be lower nasally than temporally following an increasing trend from the upper nasal through the lower nasal, lower temporal and upper temporal quadrant. Increased microvascular flux was associated with increased arteriolar and decreased venular saturations temporally as well as nasally.
Conclusions :
Functional imaging identified a pathognomonic distribution of alteration in retinal hemodynamic parameters representative of early diabetic microvascular dysfunction, which might improve the understanding of the pathophysiology of diabetic retinopathy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.