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Editors Selection IGR 18-4

Medical Treatment: Predicting second eye response

Comment by Tony Realini on:

21819 Predicting response to glaucoma therapy in one eye based on response in the fellow eye: The monocular trial, Chaudhary O; Adelman RA; Shields MB, Archives of Ophthalmology, 2008; 126: 1216-1220

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Chaudhary et al. (1278) are to be congratulated for their contribution to the ongoing discussion regarding the clinical validity of the monocular trial as a predictor of individual responsivity to topical IOP-lowering therapy. The investigators compared the absolute and relative (change in the treated eye minus change in the untreated fellow eye) IOP reductions seen in eyes undergoing monocular trials with a variety of IOP-lowering agents to the eventual IOP reduction seen in the fellow eyes subsequently treated after the monocular trial. They retrospectively reviewed their experience with 22 patients with primary open-angle glaucoma (POAG) and 27 glaucoma suspects. In their study, the correlation between IOP reductions in the firstand second-treated eyes was poor (r2 < 0.001 and r² = 0.040 for absolute and relative changes, respectively) in POAG eyes and moderate (r² = 0.348 and r² = 0.396 for absolute and relative changes, respectively) in glaucoma suspect eyes. The authors concluded that the monocular trial may be predictive of second-eye response in suspects but not in patients with POAG. In fact, the coefficients of determination (r²) reported by Chaudhary and colleagues suggest that less than 40% of the variability in second-eye IOP reduction can be explained by variation in first-eye IOP reduction in eyes of suspects. While their results were statistically significant for suspect eyes (with p < 0.001 for both), one has to question the clinical significance of the monocular trial results given that more than 60% of the variation in second-eye IOP reduction is explained by something other than the monocular trial's results.

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