Assessment of Intraretinal Microvascular Abnormalities Distribution and Their Clinical Significance in Non-Proliferative Diabetic Retinopathy Using Swept-Source Optical Coherence Tomography Angiography

Abstract

Purpose : To assess the distribution and clinical significance of intraretinal microvascular abnormalities (IRMAs) in non-proliferative diabetic retinopathy (NPDR) eyes using swept-source optical coherence tomography angiography (SS-OCTA).

Methods : In this cross-sectional observational study, 139 eyes (101 subjects, age 59.1±11.0) with NPDR underwent 12x12-mm SS-OCTA (PLEX® Elite 9000) centered on the macula and optic nerve. The resulting montage angiographic image was evaluated by two masked graders for 1) the presence of IRMAs (defined as abnormal, branching, dilated retinal vessels that stay within the inner limiting membrane) in each 6x6-mm field supertemporal [ST], inferotemporal [IT], superonasal [SN], and inferonasal [SN] to the macula, and SN and IN to the optic nerve for the extent of IRMAs (Figure 1); 2) the presence of IRMAs in the 6x6-mm center field; and 3) subtypes of IRMAs (dilated trunk, net shape, loop, sea fan, and IRMAs with tufts. Mixed-effects logistic regression models assessed the association between IRMA features and NPDR severity.

Results : IRMAs were identified in 58.3% of all NPDR eyes and were significantly more prevalent in severe (96.9%) than mild (28.8%) to moderate (70.6%) NPDR (p<0.01). The median number of affected fields was 0 for mild, 2 for moderate, and 5 for severe NPDR (p<0.01). Dilated trunk was the most frequently identified subtype (58.3%), followed by net shape (35.3%), loop (11.5%), sea fan (6.5%), and tufts (5.8%). The median number of different IRMA subtypes was 0 in mild, 1 in moderate, and 2 in severe NPDR (p<0.01). After adjusting for age, diabetes duration, and prior anti-VEGF treatment, more advanced NPDR was associated with IRMAs in the center field (OR: 8.7, p<0.01), a higher number of affected fields (OR: 2.2, p<0.01) and IRMA subtypes (OR: 4.2, p<0.01), and the presence of net shape (OR: 16.1, p=0.02), sea fan (OR: 26.0, p<0.01), and tufts (OR: 13.4, p=0.03).

Conclusions : IRMA can be observed across all stages of NPDR utilizing SS-OCTA. The number of affected fields and the variety of IRMA subtypes increases with severity. In addition to a more widespread and central distribution, specific IRMA subtypes and a greater diversity of these subtypes indicate a more severe disease.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Montage of 12x12-mm angiography with seven 6x6-mm fields