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February 2006

Nocturnal Rhythms of Intraocular Pressure

Arch Ophthalmol. 2006;124(2):269-270. doi:10.1001/archopht.124.2.269

In this issue, Hara et al%1 present their observations of 24-hour measurements of intraocular pressure (IOP) from 148 untreated Japanese patients with open-angle glaucoma. The IOP measurements in healthy Japanese subjects and untreated Japanese glaucoma patients have been recognized as being lower than those in an age-matched Western population.%2 In their study, patients with an untreated IOP higher than 21 mm Hg during office hours were excluded. For each patient, sitting and supine IOP data were recorded for awake and asleep periods. When they developed a composite 24-hour IOP curve of these patients that reflected their habitual body positions, the average IOP peaked during the nocturnal/sleep period. Despite excluding patients with office IOP higher than 21 mm Hg, they observed that 20% of their patients actually had an IOP exceeding 21 mm Hg during the nocturnal/sleep period. They also recognized that there were fewer IOP peaks during the nocturnal/sleep period when measurements in the sitting position only were considered. These results confirm previous observations%3 and help to reconcile differences observed with earlier studies in which only sitting IOP was obtained.%4,5

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