Effect of laser photocoagulation on the retinal vessel diameter in branch and macular vein occlusion.

OBJECTIVE To investigate the response of retinal vessel diameters to photocoagulation treatment and their role for the success of laser treatment in patients with retinal vein occlusion. METHODS The study included 14 patients with branch vein occlusion or macular vein occlusion. The ophthalmologic examination included best-corrected visual acuity, biomicroscopy, fundus photography, and fluorescein angiography. Retinal vessel diameters were quantified before and after laser photocoagulation using a retinal vessel analyzer. MAIN OUTCOME MEASURE Retinal vessel diameters. RESULTS In cases manifesting macular vein occlusions, no significant change of the vessel diameter in any vessel was observed during the follow-up period. In the group with branch vein occlusion, all vessels tended to constrict after the laser photocoagulation. The effect of laser treatment on retinal vessel diameters was significant for superotemporal (P =.045, analysis of variance [ANOVA]) and inferotemporal branch veins (P =.03, ANOVA). Vasoconstriction was more pronounced in the occluded branch veins (P =.009, ANOVA) compared with the nonaffected veins (P =.12; ANOVA). The change of visual acuity after 3 months was correlated with the change of vessel diameter 3 months after laser treatment for occluded venular branches (r = 0.78, P =.02, linear regression). There was no correlation between the number of laser burns and the change of vessel diameters in the affected veins in this period (r = 0.12, P =.75, linear regression). CONCLUSIONS Our results show that retinal photocoagulation in patients with branch vein occlusion has a vasoconstrictive effect on occluded veins. The correlation between the change in visual acuity and the change in vessel diameter indicates that branch vein constriction after photocoagulation may be an early indicator of the success of laser treatment.