Changes in the parafoveal and perifoveal vessel density and the area of foveal avascular zone in patients with diabetic retinopathy

Abstract

Objective To investigate the parafoveal and perifoveal vessel density and the area of foveal avascular zone (FAZ) by optical coherence tomography angiography (OCTA) in diabetic patients with early diabetic retinopathy. Methods Clinical data of in-patients and out-patients with diabetes in Department of Endocrinology of Beijing Hospital from October 2015 to November 2016 were collected. All of the participants underwent examination with OCTA, and were examined for the condition of fundus according to Early Treatment Diabetic Retinopathy Study (ETDRS) international DR staging criteria. Total of 85 eyes from patients without diabetic retinopathy (NDR group) and 23 eyes with diabetic retinopathy (DR group) were checked in the study. Ninety eight eyes from healthy subjects were set as normal control. Differences of vessel density in macular region and the area of FAZ among the three groups were analyzed by analysis of variance and pairwise comparison was done by using LSD method. Results The difference in mean vessel density between the control and patients with diabetes was statistically significant (51%±4% vs 50%±5%, F=5.828, P=0.017). Vessel densities in fovea beside macula lutea, upper part of macula lutea,upward margin of central fovea, temporal margin of central fovea, nasal margin of central fovea of normal control group were all significantly higher than those in patients with diabetes (F=4.794, 6.677, 6.117, 7.294, 4.656, P<0.05). The size of FAZ of control group was significantly smaller than that in patients with diabetes [(0.29±0.08) vs (0.33±0.09) mm2, F=12.30, P=0.001]. Mean vessel densities of control group, NDR group and DR group were tapering off (51%±4% vs 50%±5% vs 47%±4%, F=10.605, P=0.000), and area of FAZ of the three groups increased instead [(0.29±0.08) vs (0.33±0.07) vs (0.38±0.10) mm2, F=10.892, P=0.000]. Therewas significant difference in vessel density in the macular region between the normal control and DR group [mean deviation (I-J value) 4.422, P=0.000], while no significant differences between the normal control and NDR group was found (I-J value 1.196, P=0.051). Significant difference in FAZ area between the normal control and NDR group, and between normal control and DR group were found with LSD method (I-J value 0.043, 0.091, both P<0.05). Similarly, significant differences in mean vessel densities in macular region and FAZ area were found between the NDR group and DR group (I-J value 3.227, 0.048, both P<0.05). Conclusion OCTA can detect early ischemia changes in macular region such as lower vessel density, greater size of FAZ, thus is helpful for early intervention. Key words: Diabetic retinopathy; Optical coherence tomography angiography; Macula lutea; Foveal avascular zone; Vessel density