E.J.H.GOH1, S.B.B.TUN2, N.Z.B.S.HAMID2, G.C.M.CHEUNG3, R.AGRAWAL4, V.A.BARATHI2
MOH Holdings Pte Ltd (MOHH)1, Singapore Eye Research Institute, Singapore2, Singapore National Eye Centre3, Tan Tock Seng Hospital4
Diabetic retinopathy (DR) is a leading cause of blindness worldwide. First-line treatment involves pan-retinal photocoagulation (PRP) of the retina to reduce the impetus for neovascularisation. The choroidal circulation is responsible for 85% of ocular blood supply. Studies have shown significant reduction in choroidal blood flow post-PRP. However, these studies were based on patients with diabetic retinopathy, also subject to confounding factors such as disease severity, lifestyle and treatment compliance.
We evaluated changes in choroidal angioarchitecture on optical coherence tomography (OCT) post-PRP in non-human primates (NHPs) using the choroidal vascularity index (CVI), a sensitive method that detects changes in choroidal angioarchitecture.
Four (n = 8 eyes) healthy NHPs (Macaca fascicularis) were treated with PRP on Day 0 in both eyes. Laser-induced lesions were confirmed and severity scored using fluorescein angiography from grade 1 (no hyperfluorescence) to 4 (bright hyperfluorescence and leakage) by a masked investigator on Day 14 and 28. Enhanced depth imaging OCTs were also performed at the same time and segmented by modified image binarization technique, calculating the CVI.
In 7 of 8 eyes, there was a decrease in choroidal vascularity at day 14 and 28. 1 eye showed a converse increase in vascularity of 0.44%. However, the same primate’s other eye showed a corresponding decrease of 14.10%. There was an overall decrease in choroidal vascularity in both eyes in all primates (mean percentage 7.09%).
This study evaluates the treatment outcomes of PRP on the choroidal vasculature in healthy, NHPs, eliminating potential confounding factors in human subjects.