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A hot topic in glaucoma research recently is whether or not the variation (or fluctuation) of intraocular pressure (IOP) is an independent risk factor for glaucoma development and progression. The stage for debate was originally set by a report showing IOP variation during the diurnal/wake period as an independent risk factor for glaucoma progression (Asrani et al., J Glaucoma 2000; 9: 134-142). This finding, if proved to be true, can have a huge impact on the clinical management of glaucoma. For example, a single IOP reading during office hours will become a poor practice. Determination of diurnal IOP variation will need multiple IOP measurements preferably beyond office hours and spread over several days due to the uncertainty involved. Among the articles joined the debate, the present report by Jonas et al. (920) was probably the most comparable to the original report; both studies covered the whole diurnal/wake time period (the sleep period was not included), 5 IOP measurements were taken daily in the sitting position, and the follow-up periods were for four to five years. In some aspects, the present study may be regarded as more comprehensive since it had a larger sample size (458 patients versus 64 patients) and the IOP readings were obtained using the gold standard (Goldmann tonometry by eye professionals versus self-tonometry by patients). Unfortunately, results form the present study showed that the IOP itself, not the diurnal IOP variation, had a significant influence on the rate of glaucoma progression.
IOP measurements outside office hours are still very valuable since these readings may show an IOP level higher than the office-hour IOP and the peak IOP may occur frequently outside office hoursWe don't expect the debate will be over soon since not enough is known about IOP variation even with a several snapshots of IOP throughout the day. The jury for the debate may need to wait until the time when a device of continuous IOP monitoring is available. Using such a device, a prospective clinical trial on glaucoma progression can be judged side-by-side with data of real-life IOP variation. For now, IOP measurements outside office hours are still very valuable since these readings may show an IOP level higher than the office-hour IOP and the peak IOP may occur frequently outside office hours; these topics are not under debate.