The uniocular drug trial and second-eye response to glaucoma medications

To determine if the intraocular pressure (IOP) reduction observed in a uniocular trial correlates with the IOP reduction seen in the fellow eye when the same medication is then administered to the second eye of patients with glaucoma.

Observational case series.

Fifty-two patients with bilateral glaucoma.

Glaucoma patients underwent uniocular trials of various glaucoma medications, then subsequently received the same drug in the fellow eye. The IOP reduction observed in the first eye was compared with that observed in the second eye to determine correlation.

Intraocular pressure reduction in fellow-eye pairs.

Intraocular pressure dropped a mean of 5.7+/-3.8 mmHg (mean +/- standard deviation) in the first eye after a uniocular trial, and 2.8+/-3.3 mmHg in the second eye after bilateral use. Regression analysis demonstrated a poor correlation between first-eye and second-eye response to the same medication (r(2) = 0.0174). To minimize possible contralateral IOP effects of first-eye therapy, a subset of 26 patients treated with latanoprost (which has little if any contralateral IOP effect, due to rapid systemic metabolism) was studied, with no improvement in correlation (r(2) = -0.0023).

Uniocular trials of glaucoma medications do not adequately predict second-eye IOP responses to the same medications. If both eyes of a glaucoma patient require IOP reduction, one should not assume that magnitudes of response will be equal in both eyes. The effect of a given medicine must be assessed independently for each eye.