Evaluation of retinal vascularization in diabetic retinopathy before and after panretinal photocoagulation using optical coherence tomography angiography

Abstract

Purpose : Previous studies have shown that retinal blood flow is reduced after panretinal photocoagulation (PRP) for diabetic retinopathy using laser speckle flowgraphy. The purpose of our study was to describe modifications of retinal vascularization on optical coherence tomography angiography (OCT A) after PRP for diabetic retinopathy.

Methods : This prospective observational longitudinal clinical study included 35 eyes of 24 patients with severe nonproliferative diabetic retinopathy (n=17) or proliferative diabetic retinopathy (n=18). Exclusion criteria were macular edema, media opacities, and prior PRP. Macular vascular density was measured on 6x6mm scans, and peripapillary vascular density was measured on 4.5x4.5mm scans using OCT A (Optovue Inc, Fremont, California) at baseline, after 3 PRP sessions (M2), and 3 months after PRP (M5). Peripheral vascularization was assessed by automated reconstruction of five 9x9mm scans (PLEX Elite 9000 Swept Source OCT, Zeiss, Dublin, California) at M0 and M5.

Results : The mean whole image macular vascular density did not significantly change during the follow-up period compared to baseline (M0: 45.58%±0.60; M2: 44.48%±0.67; M5: 45.26%±0.57 for superficial vascular complex ; p=0.99 and 0.98; and M0: 45.39%±0.73; M2: 44.63%±1.28; M5: 45.49%±0.86 for deep capillary plexus; p=0.99 and 0.98). Mean global RNFL thickness was significantly increased at M2 but did not differ from baseline at M5 (M0: 111.0µm±2.4; M2:119.4µm±2.1; M5: 110.3µm±3; p=0.01 and p=0.91). Peripapillary vascular density was decreased at M2 but not at M5 in nasal superior (M0 : 45.1%±0.9; M2: 42.7%±1.2; M5: 45.2%±0.1, p<0.01 and p=0.98), superotemporal (M0: 51.0%±0.8; M2: 48.57%±1.5; M5: 50.5%±1.0; p<0.01 and p=0.93), and inferonasal quadrant (M0:47.7%±1.0; M2: 44.8%±1.6; M5: 45.17%±1.2; p<0.01 and p=0.72). Ten eyes had neovessels elsewhere or on the disc at baseline. After PRP, neovessels morphology showed pruning in 5 cases, and worsening of preexisting vitreoretinal tractions in 3 cases.

Conclusions : Macular vascular density does not change after PRP. A transient elevation of RNFL thickness is associated with a reduction of peripapillary vascular density. Wide-Field OCT A is useful to follow morphologic changes of neovessels after PRP.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.