Abstract
Abstract: :
Purpose: We have previously demonstrated that the uniocular drug trial in glaucoma does not predict the second eye’s IOP response to the same medication, potentially because (a) fellow eyes respond independently to a given medication, or (b) medication–independent (spontaneous) IOP changes vary over time, such that IOP changes seen during uniocular trials cannot be directly compared to second–eye trials at a later timeframe, or (c) both. This study was carried out to determine which of these potential explanations explains why the uniocular drug trial fails to predict second–eye IOP response. Methods: A retrospective chart review identified 43 glaucoma patients who underwent addition of an IOP–lowering medication of the physician’s choice to both eyes on the same day. Patients were on zero (81%) or one (19%) IOP–lowering medication at the time the medication was added in this study. Baseline IOP was the mean IOP of the treatment initiation visit and the immediately preceding visit (to reduce regression to the mean). 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. 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–squared = 0.70, p < 0.0001). Conclusions: Fellow eye pairs exhibited marked symmetry in IOP responses to IOP–lowering medications. The uniocular drug trial likely fails due to temporal variability in spontaneous non–therapeutic IOP fluctuations, not due to independence of therapeutic IOP responses between fellow–eye pairs.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials