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Editors Selection IGR 20-2
Medical Therapy: Monocular trials inaccurately assess IOP reduction
Comment by Tony Realini on:
27192 The utility of the monocular trial: Data from the ocular hypertension treatment study, Bhorade AM; Wilson BS; Gordon MO et al., Ophthalmology, 2010; 117: 2047-2054
Utilizing the robust Ocular Hypertension Treatment Study database, Bhorade et al. (1895) have made an important contribution to the ongoing evaluation of the monocular drug trial as a means of assessing therapeutic response to IOP-lowering therapy. Following the original OHTS study, participants in the observation group were offered treatment. As in the original OHTS protocol, these subjects initiated treatment using the monocular trial. This is a well-designed and appropriately-powered post hoc analysis of the 212 participants who initiated therapy with a prostaglandin analogue (as this class is not associated with a substantial contralateral crossover effect on IOP). IOP was measured on the visit when treatment was started and also at the following visit. The unadjusted and adjusted monocular trial IOP changes were calculated as the change in the treated eye between these two visits with and without adjustment for the IOP change in the fellow untreated eye over the same time span.
The best way to assess medication efficacy is to collect multiple pre-treatment and multiple on-treatment IOP measurements and determine average IOP reduction from these data
These values were correlated with the gold standard IOP reductions derived by taking the difference of three averaged pre-treatment IOP readings and three averaged on-treatment readings; since this analysis was in the setting of the longitudinal OHTS, these key data points were available. This gold standard mean IOP reduction correlated poorly with both the unadjusted and adjusted monocular trial IOP reductions (r = 0.40 and r = 0.41, respectively). The investigators conclude that the monocular trial inaccurately assesses longterm mean IOP reduction and that to date the best way to assess medication efficacy is to collect multiple pre-treatment and multiple on-treatment IOP measurements and determine average IOP reduction from these data.
An inconvenient method that works, is preferred over a convenient method that does not
This can be inconvenient, time-consuming and expensive. An inconvenient method that works, however, is preferred over a convenient method that does not.
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