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Editors Selection IGR 16-4

Intraocular Pressure: Prediction fellow-eye response

Comment by Tony Realini on:

46545 Improved prediction of fellow-eye response in one-eye trials using multiple intraocular pressure measurements, Wakabayashi Y; Higashide T; Sugiyama K, Japanese Journal of Ophthalmology, 2011; 55: 480-485

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Wakabayashi et al. (1277) have added to the monocular trial debate with a prospective study in which 16 patients with POAG (14) or OHTN (2) underwent IOP measurements on no medications on two different days, then underwent IOP measurements on monocular therapy (worse eye treated) on two different days, and finally underwent IOP measurements on bilateral therapy on two different days. This differed from our prospective study by the addition of a second assessment on monocular therapy. The investigators hypothesized that multiple assessments on monocular therapy would improve the monocular trial's prediction of the fellow eye's response to therapy. In fact, they found that adding the second assessment on monocular therapy substantially improved prediction of the fellow eye's eventual response (the coefficient of determination improved from 0.17 to 0.57). I applaud their study design and analysis but have three points to make. Firstly, they provide no sample size or power calculation to justify such a small number of patients. Secondly, as we have said previously, asking the monocular trial to predict second-eye response is perhaps less clinically relevant than asking the monocular trial to predict the trial eye's long-term response to medication. And thirdly, their protocol required six visits on six different days. Why work so hard and spend so much time and money (and delay treatment to the fellow eye for so long) to mathematically model the fellow eye response when they could have treated both eyes from the start and known the true fellow eye response much sooner?

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