Effects of photocoagulation on ocular blood flow in patients with severe non-proliferative diabetic retinopathy

Purpose To investigate ocular blood flow and correlations between ocular blood flow and variables in patients with severe non-proliferative diabetic retinopathy (S-NPDR) following panretinal photocoagulation (PRP). Methods In this retrospective, cross-sectional study, the blood flow on the optic nerve head (ONH) and choroid was assessed with laser speckle flowgraphy (LSFG) using the mean blur rate (MBR) in 76 eyes of 76 patients with S-NPDR who underwent PRP, 39 eyes of 39 patients with S-NPDR who did not undergo PRP, and 71 eyes of 71 normal subjects. The correlation between MBR and variables, including visual acuity (VA) and choroidal area determined by binarization method, was analyzed. Results The mean age was 62.9 11.9 years in the S-NPDR with PRP eyes, 55.6 11.4 years in the S-NPDR without PRP eyes, and 60.3 11.1 years in the normal subject eyes. The ONH MBR in vessel and tissue areas and the choroidal MBR were significantly lower in the SNDR with PRP group than in the other groups (p < 0.001, p < 0.001, and p < 0.001, respectively). The luminal and the stromal areas were significantly smaller in the S-NDR with PRP group than in the other groups (p < 0.001 and p < 0.001, respectively). LogMAR best corrected visual acuity (BCVA) exhibited significant negative correlation with the ONH MBR in vessel (r = 0.386, p < 0.001), tissue (r= 0.348, p < 0.001), and the choroid MBR (r= 0.339, p= 0.002) in the S-NDR with PRP group. Stepwise multiple regression analysis demonstrated that BCVA was a common independent factor associated with the ONH MBR in vessel, tissue, and the choroidal MBR in the S-NDR with PRP group. Conclusions ONH and choroid MBR in addition to choroidal component, including the luminal area, were significantly lower in eyes of patients with S-NPDR after PRP compared with no PRP and normal subjects group. This could suggest that the significantly reduced ocular blood flow in PRP-treated S-NPDR eyes correlated with long-term decreased post-PRP luminal area and visual acuity.