The purpose of this study was to investigate the prophylactic effect of brimonidine 0.15% on intraocular pressure (IOP) elevation and the risk factors for its elevation after intravitreal triamcinolone acetonide injection (IVTA).

A prospective, randomized clinical trial was conducted on 67 eyes of 64 patients undergoing IVTA. Eyes were randomly divided into two groups, those which had used brimonidine 0.15% (40 eyes) and those which had not used it (27 eyes). IOP was measured preoperatively, at one week, and monthly until six months post-injection in each group.

The mean post.injection IOP at one week was 11.93±3.36 mmHg for the group that had used brimonidine and 13.58±3.25 mmHg for the group that had not used it. The difference between the two groups was statistically significant at one week ( p =0.049), but others were not statistically significant. An elevation in the IOP of more than 22 mmHg was seen in 8 eyes (20%) in the group using brimonidine and in 7 eyes (25.9%) in the group not using brimonidine. There was no difference in the incidence of IOP elevation between the two groups.

Prophylactic use of brimonidine 0.15% will prevent sudden IOP elevation and will, therefore, prevent damage to the retina and optic nerve. However, in the long term, there is no prophylactic effect of brimonidine 0.15% on IOP elevation because there was no difference in the incidence of IOP elevation of more than 22 mmHg between the two groups.