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T. Kida, J. H. K. Liu, R. N. Weinreb; Effects of Aging on 24-Hour Blood Flow in the Optic Nerve Head and the Macula Area in Healthy Human Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):6037.
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To study effects of aging on 24-hour blood flow in the optic nerve head and in the macula area in healthy human eyes.
Twelve older volunteers with healthy eyes (age 50-80 years) and fifteen healthy younger volunteers (age 20-25 years) were housed for one day in a sleep laboratory with 16-hour diurnal/wake period and 8-hour nocturnal/sleep period. Every two hours, intraocular pressure (IOP) and systemic blood pressure were measured after 5 minutes in the sitting position. Ocular perfusion pressure was calculated. The corresponding blood volume, flow, and velocity in the optic nerve head and in the macula area were measured using a scanning laser Doppler flowmeter. The diurnal-to-nocturnal changes in the blood flow parameters were compared between the older group and the younger group.
In the older group, nocturnal mean IOP was significantly lower than diurnal mean IOP. There was no significant difference in the mean blood pressure between the nocturnal and diurnal periods, neither the ocular perfusion pressure (nocturnal, 53.4 ± 7.8 mm Hg and diurnal, 54.2 ± 7.0 mm Hg; mean ± SD). However, there were significant diurnal-to-nocturnal decreases in blood volume, flow, and velocity in the optic nerve head and in the macula area. The nocturnal blood flow was 324.6 ± 75.7 (arbitrary unit) and the diurnal blood flow was 365.7 ± 67.7 in the optic nerve head. The nocturnal blood flow was 295.3 ± 72.1 and the diurnal blood flow was 312.1 ± 71.7 in the macula area. In the younger group, IOP was higher and mean blood pressure was lower during the nocturnal period than during the diurnal period. The nocturnal ocular perfusion pressure, 46.8 ± 5.6 mm Hg, was significantly lower than the diurnal ocular perfusion pressure, 50.9 ± 6.3 mm Hg. There was no significant difference in any blood flow parameter, volume, flow, or velocity, in the optic nerve head and in the macula area between the nocturnal period and the diurnal period. Compared the two age groups, nocturnal ocular perfusion pressure was higher in the older group. In addition, both diurnal and nocturnal blood volumes in the macula area were smaller in the order group.
Significant diurnal-to-nocturnal decreases in blood flow occur in the optic nerve head and in the macula area in the older volunteers, which are independent from the change of ocular perfusion pressure.
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