Effect of panretinal photocoagulation on retina and choroid in diabetic retinopathy: An optical coherence tomography angiography study

Background: To analyze the quantitative changes in both macular, and choroidal thickness, and micro-vascularization after panretinal photocoagulation (PRP) in eyes with proliferative diabetic retinopathy (PDR) or severe non-proliferative diabetic retinopathy (NPDR) by using optical coherence tomography angiography (OCT-A).Methods: The patients diagnosed with severe NPDR or PDR according to the Early Treatment Diabetic Reti-nopathy Study (ETDRS) and decided to be treated with PRP were included in this prospective and observational study. Ten eyes of 10 patients with PDR and twelve eyes of 12 patients with severe NPDR were examined. Macular scans (6 x 6 mm) were obtained from OCT-A at baseline and at month 6 after PRP. Subfoveal choroidal thickness (SFCT) measurements that were obtained through the foveolar center on a high-definition line scan were recorded.Results: Best-corrected visual acuity (BCVA) significantly decreased (p = 0.018), central foveal thickness and mean parafoveal thickness significantly increased (p < 0001 and p < 0.001, respectively) six months after PRP. The thickness of all parafoveal retinal quadrants (temporal, superior, nasal, inferior) increased (p = 0.001, p = 0.003, p < 0.001, p < 0.001, respectively) and mean parafoveal, parafoveal temporal, and parafoveal nasal vessel density of the deep capillary plexus (DCP) significantly decreased six months after PRP compared with the baseline values (p = 0.023, p = 0.041, p = 0.018, respectively).Conclusions: The parafoveal vessel density of DCP decreased significantly 6 months after PRP in eyes with PDR or severe NPDR. While the difference in SFCT and choroidal flow density was not significant from the baseline; central and parafoveal retinal thickness increased and BCVA decreased significantly 6 months after PRP treatment.