Name

Comparaison de la perte capillaire dans les régions maculaires et en moyenne périphérie dans la rétinopathie diabétique en OCT-angiographie grand champ

The growing availability of wide-field OCTA has allowed evaluation of retinal microvasculature in a wider area up to the equatorial region. Previous studies showed a significant increase in the percentage of nonperfusion area as diabetic retinopathy (DR) severity increases. The aim of the present study was to compare the capillary loss beetween macular versus mid-periphery regions in patients with different degrees of DR severity and healthy control patients using SS- OCTA.

This is an observational case series conducted in Lariboisiere hospital, Paris, France beetwen august and october 2020. Inclusion criteria were confirmed diagnosis of diabetes with or without non proliferative DR. Exclusion criteria were the presence of a diabetic macular edema, previous focal macular laser and panretinal photocoagulation or intravitreal injection; intraocular surgery in the last 6 months, glaucoma, low quality OCTA images (signal index lower than 7 or significant motion artifacts). DR stage was classified based on ultra-widefield fundus photography using the ETDRS-simplified American Academy of Ophthalmology DR grading scale. Diabetic eyes were divided into two groups for statistical analysis : no DR or mild non-proliferative DR (mild NPDR group) ; moderate or severe NPDR (severe NPDR group). These groups were compared to a control group of age-matched healthy volunteers. For each eye, four 3x3mm OCTA volumes were acquired at 4 fixation points, including the following scans : central, superior, inferior and temporal. Each peripheral volume was acquired at the same location for all patients and the mean distance of mid-periphery scans was 6,7mm from the fovea center. To quantify the capillary density (CD), each 3x3mm en face SS-OCTA images were converted into binary images using ImageJ according to previously reported methods. CD loss was calculated as the percentage of CD value in the healthy eyes in the same area.

A total of 24 eyes from 24 patients (18 men, mean age of 57,6+/-13,8 years) were included, including 8 eyes in the mild NPDR group and 8 eyes in the severe NPDR, and 8 were healthy control eyes. The CD of superficial capillary plexus (SCP) was significantly decreased in the severe NPDR group compared with controls in the central area (33.8 vs 38.1%, p=0.0022), in the superior mid-periphery (27.5 vs 33.0%, p=0.0022) and in the inferior mid-periphery (26.2 vs 31.2%, p=0.0093). The CD of deep capillary complex  (DCC) was significantly decreased in eyes with severe NPDR compared with controls in the superior mid-periphery (19.5 vs 25.0%, p=0.0012) and in the inferior mid-periphery (17.6 vs 25.4%, p=0.0003). A significant higher CD loss was found in the mid-periphery compared to the central area in the DCC in the group of severe NPDR (CD was 73,14% of the normal value in the mid-periph vs 90,56% in the center, p=0,0036). A significant higher ratio of central CD/mid-periphery CD was found in the DCC (1,237 vs 1,00, p=0,0005), while no difference was found in the SCP in the severe NPDR group compared with controls.

In this case series, we aimed at comparing the capillary loss in the center vs mid-periphery in mild and severe NPDR. The capillary loss in the SCP did not differ in the mid-periphery compared with the central area in both mild and servere NPDR. Conversely, the capillary loss in the DCC was not homogenous, comparing central CD to mid-periphery and was higher in mid-periphery in the DCC. Similarly, the ratio of central CD/mid periph CD was significantly higher in eyes with severe NPDR compared with control and mild NPDR groups.

The capillary loss in the DCC of NPDR eyes was heterogeneous in the mid-periphery vs center.