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Editors Selection IGR 15-2

Medical treatment: Monocular therapeutic drug trial

Comment by Tony Realini on:

20982 Discrepancy of the intraocular pressure response between fellow eyes in one-eye trials versus bilateral treatment: Verification with normal subjects, Takahashi M; Higashide T; Sakurai M et al., Journal of Glaucoma, 2008; 17: 169-174

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Takahashi et al. (599) tackled a con-troversial, but clinically relevant topic by evaluating the clinical utility of the monocular therapeutic drug trial. Forty-one normal Japanese subjects received latanoprost for seven days in the right eye, then a 2-or-more month washout, then latanoprost for seven days in the left eye. A second group of 41 normal Japanese subjects received bilateral latanoprost for seven days. IOP was measured at three time points on Day 0 and Day 7 for each treatment period. Correlation of mean diurnal IOP change in right and left eyes of individual subjects undergoing monocular trials was poor (r² = 0.102) even when correcting for the change in IOP from the untreated fellow eyes (r² = 0.097). Conversely, correlation of mean diurnal IOP change in right and left eyes of individuals undergoing simultaneous bilateral treatment was high (r² = 0.849). Using normal subjects was an odd aspect of the study design. Non-glaucomatous Japanese eyes with mean IOP in the 13-14 mmHg range likely undergo less spontaneous IOP variation than untreated glaucomatous eyes. This coupled with the use of latanoprost ‐ with minimal contralateral crossover effect ‐ should have produced a best-case scenario in terms of correlation of fellow-eye IOP changes during monocular trials. In fact, it did not. Their data were essentially identical to our own prior studies, demonstrating abysmal correlation of first-treated and second-treated eyes using the monocular trial, but demonstrating excellent correlation between right and left eyes when treated simultaneously. Taken in the aggregate, their data and our data and the work of others recently published, all suggest that spontaneous IOP fluctuations may be similar between fellow eyes during the same time period, but vary from day to day within eyes. While this study in normals may not be made general to glaucomatous eyes, their data conform superbly to published data in glaucomatous eyes. The authors conclude ‐ erroneously, we believe ‐ that the monocular trial fails because fellow eyes respond asymmetrically to latanoprost, even though their data (and others') support that the monocular trial fails primarily because of asymmetry of spontaneous IOP fl uctuations.

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