Pilot study of doppler optical coherence tomography of retinal blood flow following laser photocoagulation in poorly controlled diabetic patients

Purpose. To investigate the effect of panretinal photocoagulation (PRP) on retinal blood flow and shear rate using Doppler Fourier-domain optical coherence tomography (FD-OCT) in poorly controlled diabetics with proliferative diabetic retinopathy (PDR). Methods. This was a prospective interventional pilot study in patients with a new clinical diagnosis of PDR. Retinal blood flow and vessel diameter were measured using Doppler FD-OCT according to a previously described method, immediately before PRP treatment and 7 to 8 weeks after the last PRP session. Results. Ten patients with poorly controlled PDR (mean hemoglobin A1C = 9.2 ± 2.0%) and 10 control subjects were included in the study. PDR patients had significantly lower blood flow (∼25%) than control subjects both at baseline (P = 0.01) and after PRP (P = 0.003). Compared to controls, venous and arterial velocities were significantly decreased in diabetics at baseline (∼27%; P < 0.001 and 0.017, respectively) as well as after PRP (P < 0.001 and 0.006, respectively). Compared to controls, venous and arterial shear rates were significantly reduced in diabetics at baseline (∼27%; P = 0.002, 0.03) and after PRP (P = 0.002, 0.03). PRP in this group of PDR patients did not have a statistically significant effect on retinal blood flow or vessel parameters, though there was a trend for decreased arterial diameter (P = 0.09). Conclusions. This is the first study to use Doppler FD-OCT to quantify functional changes in retinal vascular parameters in poorly controlled PDR patients. Compared to controls, blood flow parameters in these patients were decreased at baseline, but did not decrease further following PRP, with important implications related to diabetes control, endothelial function, and therapeutic response.