Abstract
BackgroundIntraocular pressure (IOP) may vary according to the change of ocular conditions. In this study, we want to assess the effect and mechanism of pupil dilation on IOP in normal subjects.MethodsWe prospectively evaluated 32 eyes of 32 patients (age; 61.7 ± 8.2 years) with normal open angles under diurnal IOP. IOP was measured every two hours from 9 AM to 11 PM for one day to establish baseline values and was measured again for one day to assess the differences after dilation. To induce dilation, we administered 2.5% phenylephrine and 1% tropicamide every 5 minutes from 8:30 AM to 8:45 AM and for every two hours from 11 AM to 9 PM to keep the pupil dilated. Diurnal IOP, biometry, Visante OCT, and laser flare photometry were measured before and after dilation.ResultsWe observed a significant increase in IOP after dilation, 1.85 ± 2.01 mmHg (p = 0.002). IOP elevation remained significant until about four hours after dilation. Thereafter, IOP decreased slowly and eventually reached pre-dilation level (p > 0.05). Flare values decreased, and the anterior chamber angle became wider after mydriasis.ConclusionsDilation of the pupil significantly and incidentally elevated IOP in normal subjects. Further related studies are warranted to characterize the mechanism of the increased IOP after dilation.
Highlights
Intraocular pressure (IOP) may vary according to the change of ocular conditions
The maximum IOP significantly increased from a mean predilation level of 13.10 mmHg ± 2.91 to a post-dilation level of 14.96 ± 3.25 mmHg (p < 0.001)
Diurnal IOP was elevated in 22 eyes (68.9%), decreased in two, and unchanged in eight
Summary
Intraocular pressure (IOP) may vary according to the change of ocular conditions. We want to assess the effect and mechanism of pupil dilation on IOP in normal subjects. IOP is a dynamic parameter and varies throughout the course of 24 hours, possibly following circadian rhythms. The mean range of diurnal IOP variation is approximately 2 to 6 mmHg in the normal population and 5 to 18 mmHg in glaucoma patients [1,2]. Clinicians are advised to conduct multiple measurements over 24 hours to assess the IOP profiles of at-risk patients. Mydriatics are regularly used to dilate pupils in patients presenting to ophthalmology clinics for assessment and follow-up of a wide variety of ophthalmic conditions.
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