Sit Arthur J, Nau Cherie B, McLaren Jay W, Johnson Douglas H, Hodge David
Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Invest Ophthalmol Vis Sci. 2008 Apr;49(4):1473-9. doi: 10.1167/iovs.07-1139.
Recent research indicates that intraocular pressure (IOP) does not decrease significantly during the nocturnal period, although aqueous humor flow decreases by 50% or more at night. This study was undertaken to investigate whether changes in outflow facility, episcleral venous pressure, or uveoscleral flow at night could account for the nocturnal IOP.
Sixty-eight eyes of 34 healthy subjects (age, 18-44 years; mean, 29) were studied. Aqueous humor flow rate, IOP, and outflow facility were measured with pneumatonometry, anterior chamber fluorophotometry, and Schiotz tonography respectively, in each eye during the mid-diurnal (2-4 PM) and mid-nocturnal (2-4 AM) periods. Nocturnal IOP, flow rate, and outflow facility were compared to the same variables during the diurnal period. Mathematical models based on the modified Goldmann equation were used to assess the conditions under which these results could be reconciled.
Supine IOP decreased slightly from 18.9 +/- 2.7 mm Hg in the mid-diurnal period to 17.8 +/- 2.5 mm Hg in the mid-nocturnal period (mean +/- SD, P = 0.001). Aqueous flow rate decreased from 2.26 +/- 0.73 to 1.12 +/- 0.75 microL/min (mean +/- SD, P < 0.001). There was a nonsignificant trend toward a nocturnal decrease of outflow facility (diurnal, 0.27 +/- 0.11 microL/min/mm Hg; nocturnal, 0.25 +/- 0.08 microL/min/mm Hg; mean +/- SD, P = 0.13).
Outflow facility measured by tonography does not decrease enough during the nocturnal period to compensate for the decreased aqueous humor flow rate. Modeling results indicate that the experimental results could be reconciled only if nocturnal changes in episcleral venous pressure and/or uveoscleral flow occurred.
近期研究表明,尽管夜间房水流量减少50%或更多,但眼内压(IOP)在夜间并未显著降低。本研究旨在探讨夜间房水流出易度、巩膜静脉压或葡萄膜巩膜途径房水流量的变化是否可解释夜间眼内压情况。
对34名健康受试者(年龄18 - 44岁,平均29岁)的68只眼睛进行研究。分别在午后中段(下午2 - 4点)和午夜中段(凌晨2 - 4点),使用气动眼压计、前房荧光光度法和修兹眼压描记法测量每只眼睛的房水流量、眼内压和房水流出易度。将夜间的眼内压、流量和流出易度与白天同一变量进行比较。基于改良的戈德曼方程的数学模型用于评估使这些结果相符的条件。
仰卧位眼内压从午后中段的18.9±2.7毫米汞柱略有下降至午夜中段的17.8±2.5毫米汞柱(平均值±标准差,P = 0.001)。房水流量从2.26±0.73微升/分钟降至1.12±0.75微升/分钟(平均值±标准差,P < 0.001)。夜间房水流出易度有不显著的下降趋势(白天,0.27±0.11微升/分钟/毫米汞柱;夜间,0.25±0.08微升/分钟/毫米汞柱;平均值±标准差,P = 0.13)。
通过眼压描记法测量的房水流出易度在夜间下降幅度不足以补偿房水流量的降低。模型结果表明,只有当巩膜静脉压和/或葡萄膜巩膜途径房水流量在夜间发生变化时,实验结果才可能相符。