Macular Capillary Nonperfusion in Eyes With Stable Laser-Treated Proliferative Diabetic Retinopathy

Importance Some eyes with proliferative diabetic retinopathy (PDR) treated to stability with panretinal photocoagulation (PRP) continue to lose vision without diabetic macular edema. One presumed cause is macular capillary nonperfusion (CNP)–associated ischemia or infarction. Natural history data of macular CNP might guide treatment trials for it. Objective To assess visual function and optical coherence tomography angiography (OCTA) changes over 12 months in PRP-treated stable eyes with PDR and macular CNP. Design, Setting, and Participants This prospective observational cohort study was conducted in a single center in the United Kingdom. Participants had stable laser-treated PDR in at least 1 eye with macular CNP and a best-corrected visual acuity (BCVA) letter score of at least 54 (Snellen equivalent ≥20/80) using Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Recruitment was from December 2019 to August 2021 and follow-up for 12 months; data were analyzed from May to July 2024. Main Outcomes and Measures Changes in BCVA, low-luminance visual acuity (LLVA), and OCTA metrics over 12 months using linear mixed-effects models with unstructured variance accounting for within-participant correlation between the eligible study eye and repeated measures across time. Results The cohort included 63 participants and 88 eyes. The mean (SD) age was 57.4 (11.9) years; 41 were male (65.1%) and 22 female (34.9%). Mean BCVA and LLVA ETDRS letter scores were 77.52 (SD, 8.0; approximate Snellen equivalent, 20/32) and 68.33 (SD, 8.9; Snellen, 20/40) at baseline and 78.76 (SD, 8.3; Snellen 20/25) and 70.20 (SD, 8.1; Snellen, 20/40) at 12 months. However, 7 participants (9.3%) lost at least 5 letters of visual acuity at 12 months. Linear mixed-effects analysis showed the foveal avascular zone (FAZ) area deteriorated over 12 months, with a mean increase of 1.80% (95% CI, 0.01%-3.63%; P = .05) at 6 months and 2.26% (95% CI, 0.29%-4.26%; P = .03) from baseline. Eyes that lost 5 or more letters had lower baseline superficial vascular density in both the 3 × 3–mm scan (mean [SD], 36.7 [4.8] vs 33.5 [2.0]; P = .006) and parafoveal area (38.7 [5.6] vs 34.7 [2.6]; P = .005). No association was found between a loss of 5 or more letters at 12 months and any baseline FAZ parameters. Conclusions and Relevance This study found that FAZ area deteriorated over 12 months in eyes with stable laser-treated peripheral retina in eyes and macular CNP. Vision loss was uncommon and more prevalent in eyes with decreased SVD at baseline rather than FAZ parameters. Longer trials may be required to observe more events of change of 5 or more letters.