Abstract
Purpose: :
To characterize the 24-hour pattern of intraocular pressure (IOP) in eyes with normal-tension glaucoma (NTG) in the habitual position.
Methods: :
41 NTG eyes of 41 patients 40 to 87 years of age were hospitalized for 24 hours. Physiological conditions were strictly administered with a 18-hour light period and 6 hour dark period. Sleep was instructed in the dark period. IOP was measured using a Tono-Pen (Mentor Ophthalmics, Santa Barbara, USA) every 2 hours (total of 8 times) for wake hours and every 3 hours (total of 3 times) for sleep hours. Measurements were taken in both the sitting position and the supine position during the sleep hours but only sitting position during the wake hours.
Results: :
Mean IOP in the dark period was significantly higher than that in the wake period in the habitual position. When compared with the nocturnal sitting IOP, the nocturnal supine IOP was significantly higher. The peak IOP appeared during the dark period in the habitual position during 24-hour monitoring. About 20% of the NTG eyes revealed IOP in the hypertensive range (24-29 mm Hg) when measured in the habitual position. Mean nocturnal IOP was not significantly different from that of diurnal IOP in the sitting position in untreated NTG eyes.
Conclusions: :
Nocturnal elevation of IOP was evident in this sample of eyes with NTG in the habitual position. The peak IOP during 24-hour monitoring occurred during the sleep period. A significant elevation in nocturnal IOP may adversely affect ocular perfusion at night in theses NTG eyes.
Keywords: intraocular pressure • circadian rhythms • intraocular pressure