Name

079 - Densité capillaire maculaire et acuité visuelle chez les patients diabétiques de type 1 avec déséquilibre glycémique chronique

Although capillary drop-out is a hallmark of diabetic retinopathy, its role in visual loss remains unclear, as some patients may have a normal visual acuity despite macular capillary loss.

Objective: To explain how visual acuity is influenced by macular vessel density in young type 1 diabetes patients with severe diabetic retinopathy but without macular edema.

Design: Retrospective study based on visual acuity and Optical Coherence Tomography Angiography data collected during a single visit. Eyes were classified into two groups: normal visual acuity (logMAR= 0) and decreased visual acuity (logMAR>0).

Settings: Lariboisière University Hospital, Paris, France, a tertiary referral center for ophthalmologic complications of diabetes.

Participants:  Twenty-two eyes of 22 type 1 diabetes patients with a median age of 30 years, with severe diabetic retinopathy, already treated by panretinal photocoagulation but without macular edema. Control group included twenty-four eyes of 12 age-matched healthy subjects with normal visual acuity.

Main outcome measures: Mean vessel density in the superficial (SVP), intermediate (ICP) and deep (DCP) retinal vascular plexuses, and in the deep capillary complex (DCC); foveal avascular zone area; visual acuity.

Thirteen out of the 22 diabetic eyes (59%) had a normal visual acuity, and 9 (41%) had a decreased visual acuity. Vessel density measured by OCTA was decreased compared to healthy age-matched controls even in diabetic eyes with normal vision (P <0.0001). However, diabetic eyes with decreased visual acuity had a lower vessel density compared to diabetics with normal visual acuity (40 vs 44.1 in the SVP, P <0.002, 34.7 vs 44.3 in the DCC, 34.8 vs 43.8 in the ICP, 15.2 vs 24.5 in the DCP, P <0.0001). The decrease was more pronounced in the DCC (ICP and DCP) than in the SVP (mean Ls = -9.6, -9.3, and -9 vs -4.5, respectively, ANOVA model). The vessel density loss in the DCP was the most marked change, and more discriminant than foveal avascular zone area enlargement between eyes with normal and decreased vision.

Several studies have shown, using OCTA, that the macular capillary density is impaired regardless of the severity of DR and that capillary non-perfusion tends to increase with DR severity. The DCC seems to be more affected than the SVP. When we analyzed the DCC as a whole, and the ICP and DCP separately, we found that the VA mainly depended on the VD in the ICP and the DCP (the inner and outer layers of the DCC, respectively), rather than in the SVP. Our results suggest that there might be a threshold of macular non-perfusion, especially in the DCP, beyond which a normal vision cannot be maintained. A significant loss of DCP perfusion could have detrimental effects on the middle retina and even on the photoreceptors. The DCP could partially contribute to the oxygen supply to the photoreceptors unlike what was assumed before.

In type 1 diabetes patients with severe diabetic retinopathy but without macular edema, visual acuity decrease mainly depends on the degree of vessel density loss in the deep capillary complex.