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Prostaglandin analogues have been widely adopted as first line treatment to lower intraocular pressure due to their efficacy, safety and ease of use once daily. Khairy and Said-Ahmed (2032) conducted a randomized, double-blind clinical trial comparing daily use to alternate daily use of travoprost 0.004% in the treatment of ocular hypertension and concluded that alternate daily use was equal in safety and efficacy as daily use in lowering IOP. One eye of each patient received daily use of travoprost served as control while the other eye received alternate daily treatment. There are several assumptions to this methodology that have been questioned by many studies: fellow eyes often exhibit asymmetric IOP response to the same medication; medications may exhibit contralateral crossover effects; and patients may not follow the treatment regimen as prescribed (Realini, Ophthalmology 2009; 116: 1237-1242).
Until we have stronger evidence suggesting equal efficacy of alternate daily use of prostaglandin analogs as well as compliance data, prescription of daily usage is unlikely to change
In addition, the sample size in this study is small, including 28 eyes of 14 patients, leading to insufficient power to detect a true different. Secondly, the relatively short-term follow-up period up to 12 weeks after initiation of therapy may not be sufficient. In order to strengthen the validity of the study, the investigators could consider a crossover design after a sufficient period to wash out the effect of previous treatment, lengthening the follow-up period, and assessing the diurnal IOP more closely, possibly including nocturnal IOP measurement. Another important clinical question is whether alternate daily use improves or worsens patient compliance. It has been shown that once daily administration is one of the major advantage of prostaglandin analogs in terms of higher patient compliance and adherence. Some have suggested that less frequent dosing than once daily may actually cause patients to more easily forget to use their medication. Adhering to a daily routine may be more habitual. Until we have stronger evidence suggesting equal efficacy of alternate daily use of prostaglandin analogs as well as compliance data, prescription of daily usage is unlikely to change.