To evaluate the correlations between office-hour intraocular pressures (IOP) and peak nocturnal IOP in healthy and glaucomatous eyes.

Retrospective review of laboratory records.

We reviewed 24-hour data of IOP collected from 33 younger healthy subjects (aged 18 to 25 years), 35 older healthy subjects (aged 40 to 74 years), and 35 untreated older glaucoma patients (aged 40 to 79 years) housed in a sleep laboratory. Measurements of IOP were taken every 2 hours using a pneumatonometer in the sitting and supine positions during the diurnal/wake period (7 am to 11 pm) and in the supine position during the nocturnal/sleep period. Correlations between average sitting or supine IOP in the right eye between 9:30 am and 3:30 pm (office hours) and peak right eye IOP during the nocturnal hours were analyzed.

The average values of supine IOP during office hours were found to have the strongest correlation with peak nocturnal IOP in older glaucoma subjects (r = .713, P < .001), whereas the correlation was less in older healthy subjects (r = .523, P < .01) and was absent in younger healthy subjects (r = .224, P = .21). The correlation between average sitting IOP values during office hours and peak nocturnal IOP was also strong in older glaucoma subjects (r = .601, P < .001) and moderate in older healthy subjects (r = .412, P < .05), but absent in younger healthy subjects (r = −.077, P = .672).

Using a modification of the diurnal IOP curve, the magnitude of peak nocturnal IOP in untreated glaucoma patients can be estimated during routine office visits. Supine IOP measurements estimate peak nocturnal IOP better than sitting measurements. This estimation may provide the clinician with valuable information regarding the nocturnal IOP peak in glaucoma patients.