advertisement
Abstract #15390 Published in IGR 1-3
Elevation of human intraocular pressure at night under moderate illumination
Liu JH; Kripke DF; Hoffman RE; Twa MD; Loving RT; Rex KM; Lee BL; Mansberger SL; Weinreb RNInvestigative Ophthalmology and Visual Science 1999; 40: 2439-2442
PURPOSE: An endogenous elevation of intraocular pressure (IOP) occurs at night in healthy young adults. The authors studied whether or not this IOP elevation can be detected under moderate illumination. METHODS: Twenty-five healthy volunteers, aged 18-25 years, were housed overnight in a sleep laboratory under a strictly controlled light-dark environment. Intraocular pressure was measured in the supine position every two hours, using a pneumatonometer. An eight-hour sleep period was assigned to each volunteer according to individual's accustomed sleep cycle. In the early part of this assigned period, sleep was encouraged with room lights off. Researchers performed IOP measurements at two time points with the aid of night vision goggles. In the middle to the late part of the assigned period, lights were turned on twice for a one-hour interval. The light intensity was the same as before the bedtime. At the ending of each light period, IOP was measured under illumination. RESULTS: Average IOP was significantly higher in the assigned sleep period versus outside the period. The trough of mean IOP occurred just before the bedtime, and then IOP gradually increased and peaked at the end of the eight-hour assigned sleep period. The difference between the trough and peak IOP was 3.5±0.7 mmHg (mean ± SEM, n=25). Within the assigned sleep period, the average IOP determined under illumination was significantly higher than the average IOP preceding the illumination. CONCLUSIONS: Elevation of IOP occurred during the assigned sleep period with two one-hour light exposures of moderate intensity. Environmental light at night had no significant effect on the nocturnal IOP elevation in healthy young adults.
Dr. J.H. Liu, Department of Ophthalmology, University of California, San Diego, La Jolla, CA 92093-0946; USA
Classification:
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
