Background: The relation between UWF fluorescein angiography (FA) and retinal non-perfusion were studied previously. The relationship between retinal thickness and retinal non-perfusion in subjects with diabetic retinopathy has not been studied using SD-OCT and UWF. Thus, in this current study we used SD-OCT to visualize the individual layers of retina and to evaluate whether the extent of non-perfusion is correlated with macular retinal layer thickness in subjects with PDR with no diabetic macular edema.
Methods: In this prospective longitudinal multicenter, randomized study a total of 36 eyes of thirty six subjects were included in final analysis. Subjects with any history of anti-VEGF therapy, steroid therapy, pan-retinal photocoagulation or vitreoretinal surgery, macular edema, or SD-OCT determined central retinal thickness (CRT) of more than 320 μm in the study eye were excluded. All subjects underwent ETDRS BCVA testing, slit lamp and indirect ophthalmoscopy examination and diagnostic testing at all visits using Optos 200Tx (Optos plc, Dunfermline, United Kingdom), Heidelberg Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) with 9X image averaging. UWFA images were obtained and then transformed to stereographic projection images using proprietary manufacturer software. Regions of non-perfusion were identified and manually graded using Image J.
Results: The mean age of the subjects was 57 ± 13 years and 19 were female. The mean total retinal thickness was significantly lower at month 12 when compared to baseline 258.47 ± 23.52 µm vs. 285.19 ± 23.62 µm (p0.05). For both the treatment arms, the mean total NPA at month 12 (280 ± 143 mm2) increased, but not significantly (p=0.12) differ, when compared with baseline (242 ± 169 mm2). Ischemic index (ISI, %), however, was significantly (p=0.009) increased at month 12 (34 ± 17) when compared with baseline (27 ± 16).
Conclusion: The total NPA was significant and independently correlated with GCL and thinning of inner retinal layers continues even after treatment. The thickness of multiple retinal sublayers appears to decrease over time in eyes receiving intravitreal aflibercept for proliferative diabetic retinopathy despite an absence of a change in peripheral non-perfusion. The underlying pathophysiology for these reductions over time warrants further investigation
