Symmetry of fellow-eye intralocular pressure responses to topical glaucoma medications

Purpose: One assumption of the uniocular drug trial in glaucoma management is that fellow-eye pairs exhibit symmetric intraocular pressure (IOP) responses when both eyes are treated with the same topical IOP-lowering medication. The purpose of this study was to determine if this assumption is true. Design: Observational case series. Participants and Controls: Forty-three patients with bilateral glaucoma or ocular hypertension who underwent bilateral treatment with a topical IOP-lowering medication. Methods: Patients were on 0 (81%) or 1 (19%) IOP-lowering medication at the time the medication was added in this study. Baseline IOP was the IOP at the treatment initiation visit, and IOP on treatment was assessed in both eyes on the first visit after addition of the medication. Linear regression of right-eye versus left-eye IOP reductions was performed. Main Outcome Measure: Correlation of right-eye and left-eye IOP responses to therapy. Results: Right eyes demonstrated a 5.0-mmHg (26.9%) reduction, and left eyes demonstrated a 4.3-mmHg (23.7%) reduction. Linear regression of right-eye IOP reduction against left-eye IOP reduction gave a slope of 0.77 (Pearson correlation coefficient, r = 0.84; r(2) = 0.70; P < 0.0001). Conclusions: Fellow-eye pairs exhibited marked symmetry in IOP responses to IOP-lowering medications. (c) 2005 by the American Academy of Ophthalmology.