Predicting response to glaucoma therapy in one eye based on response in the fellow eye: the monocular trial

To evaluate whether the change in intraocular pressure (IOP) observed in one eye after starting a glaucoma medication regimen is predictive of the change in IOP due to the same medication in the fellow eye.

A retrospective medical record review of 22 patients with primary open-angle glaucoma (POAG) and 27 glaucoma suspects who underwent monocular drug trials before the drug was added to the second eye. The absolute change in IOP from baseline and the relative change (change in treated eye minus change in fellow eye) in the first eye treated were compared with the second eye after binocular treatment.

The absolute and relative decreases in IOP of the first eye were poorly correlated with those of the second eye in patients with POAG (r(2) < 0.001; P = .97 and r(2) = 0.040; P = .38, respectively). However, they were well correlated in glaucoma suspects (r(2) = 0.348; P = .001 and r(2) = 0.396; P < .001, respectively).

The change in IOP of one eye due to a medication may be predictive of the subsequent response of the fellow eye to the same medication in glaucoma suspects, but not in patients with POAG. Using the fellow eye as a control may confer a more accurate portrayal of the true therapeutic effects of a medicine, although further study is needed to support both of these findings.