What day of the week is IOP lowest?

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Intraocular pressure (IOP) varies by season with significantly higher IOPs noted in winter compared with summer months, according to a study published in the British Journal of Ophthalmology. In addition, researcher found IOP to be lower on Friday compared to the other days of the week.

In this prospective, open-label, multicenter observational study, data from 22 patients with primary open-angle glaucoma who had undergone placement of an intraocular telemetric sensor at the time of cataract surgery and self-measured their IOP at least 4 times a day for an average of 721 days, were included.

IOPs were lowest on Friday, highest on Wednesdays, and found to vary significantly throughout the year with a seasonal pattern.

The authors concluded that this study confirmed previously observed seasonal variations of IOP although an explanation for this is not yet known.


Mansouri K, Gillmann K, Rao HL, et al. Weekly and seasonal changes of intraocular pressure measured with an implanted intraocular telemetry sensor. B J Ophthalmol. 2020; http://dx.doi.org/10.1136/bjophthalmol-2020-315970



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