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John H. K. Liu, Daniel F. Kripke, Michael D. Twa, Rivak E. Hoffman, Steven L. Mansberger, Katharine M. Rex, Christopher A. Girkin, Robert N. Weinreb; Twenty-Four–Hour Pattern of Intraocular Pressure in the Aging Population. Invest. Ophthalmol. Vis. Sci. 1999;40(12):2912-2917.
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purpose. To characterize the 24-hour pattern of intraocular pressure (IOP) in a
sample of the aging human population.
methods. Twenty-one healthy volunteers 50 to 69 years of age were housed in a
sleep laboratory for 24 hours. Experimental conditions were strictly
controlled with a 16-hour light period and an 8-hour dark period. Sleep
was encouraged in the dark period. Intraocular pressure was measured
using a pneumatonometer every 2 hours (total of 12 times). Measurements
were taken in both the sitting position and the supine position during
the light/wake period but only in the supine position during the dark
results. When the sitting IOP data from the light/wake period and the supine IOP
data from the dark period were considered, elevation and reduction of
IOP occurred around the scheduled lights-off and lights-on transitions,
respectively. Mean IOP in the dark period was significantly higher than
mean IOP in the light/wake period. The trough appeared at the end of
the light/wake period, and the peak appeared at the beginning of the
dark period. The magnitude of trough-peak difference was 8.6 ±
0.8 mm Hg (mean ± SEM). Cosine fits of 24-hour IOP data showed a
significant 24-hour rhythm. When IOP data from just the supine position
were analyzed, the trough-peak IOP difference was 3.4 ± 0.7 mm
Hg, with similar clock times for the trough and the peak. Cosine fits
of supine IOP data showed no statistically significant 24-hour rhythm.
conclusions. Nocturnal elevation of IOP occurred in this sample of the aging
population. The trough of IOP appeared at the end of the light/wake
period, and the peak appeared at the beginning of the dark period. The
main factor in the nocturnal IOP elevation appeared to be the shift
from daytime upright posture to supine posture at
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