Retinal vessel analyzer measurements of the effect of panretinal photocoagulation on the retinal arteriolar diameter in diabetic retinopathy.

Purpose: The purpose of this study was to investigate the effect of panretinal photocoagulation (PRP) on the retinal arteriolar diameter in patients with diabetic retinopathy using a retinal vessel analyzer.

Methods: Ten eyes of 6 consecutive patients with type II diabetes and severe nonproliferative or proliferative diabetic retinopathy were studied prospectively. Measurements of the retinal arteriolar diameter were performed before the first photocoagulation session and after the end of the PRP treatment.

Results: Retinal arteriolar diameter before PRP was 131 +/- 15 arbitrary units and decreased to 112 +/- 14 arbitrary units after PRP (P = 0.012). There was a significant vasoconstriction of 13.8% +/- 8.3% following PRP. Mean visual acuity before and after PRP was 0.31 +/- 0.36 logarithm of the minimal angle of resolution and 0.28 +/- 0.30 logarithm of the minimal angle of resolution, respectively (P = 0.68). There was no significant change in mean arterial pressure before and after PRP (P = 0.89). There was no correlation between the visual acuity change or the number of laser burns and the percentage change in the retinal arteriolar diameter (P > 0.1).

Conclusion: Panretinal photocoagulation has a vasoconstrictive effect on retinal arterioles in patients with severe nonproliferative or proliferative diabetic retinopathy. These results are consistent with an autoregulatory response of the retinal circulation to increased inner retinal oxygen tension after PRP. The retinal vessel analyzer is a fast, accurate, noninvasive, online measuring system for the study of the retinal vascular response to PRP in patients with diabetic retinopathy.