Abstract
Purpose:
To characterize the 24-hour rhythm of intraocular pressure (IOP) in young, myopic, untreated open-angle glaucoma (OAG) patients with normal baseline IOP in the habitual position
Methods:
Sixty-four young, myopic OAG eyes, ages 18 to 40 years, with moderate to severe myopia (≤-3 diopters) and 56 age-matched young, emmetropic (≥-1.5 diopters) OAG eyes (control group) with normal baseline IOP were prospectively recruited and underwent 24-hour measurement of IOP and systemic blood pressure (BP) in the habitual position. In the wake period, IOP and BP were measured in the sitting position while they were measured in the supine position followed by sitting position after a 5-minute rest in the sleep period
Results:
In young, myopic OAG group, the average habitual IOP was higher than the control group in both diurnal and nocturnal period (P=0.01, 0.02, respectively). In both myopic and control OAG groups, the average nocturnal IOP in the supine position was higher than the average diurnal IOP in the sitting position. However, the magnitude of this IOP elevation during nocturnal period was significantly less in the myopic group than in the control group (0.2 mmHg vs. 1.2 mmHg, P<0.001). In both myopic and control OAG groups, the average diurnal IOP in the sitting position was higher than the average nocturnal IOP in the sitting position. There was no difference in the 24-hour rhythms of mean arterial BP between the two groups
Conclusions:
In the habitual body position, young, myopic OAG eyes with normal baseline IOP exhibit higher 24-hour IOP at both diurnal and nocturnal period than the age-matched emmetropic eyes. IOP increases at night in both OAG groups, but the magnitude of the increase is significantly less in the myopic group than in the control group. The difference in globe size may result in less pronounced nocturnal habitual IOP elevation in young, myopic glaucomatous eyes