Circadian (24-hour) Pattern of Intraocular Pressure and Visual Field Damage in Eyes with Normal-Tension Glaucoma

Abstract

To characterize the circadian (24-hour) pattern of habitual-position intraocular pressure (IOP) and its association with visual field (VF) damage in eyes with normal-tension glaucoma (NTG). A total of 177 eyes with NTG were examined over a 3-year period. IOP was recorded at 8 AM, 10 AM, 12 PM, 2 PM, 4 PM, 6 PM, 8 PM, 10 PM, 12 AM, 3 AM, and 6 AM by a single, well-trained ophthalmology resident using a hand-held tonometer. The circadian pattern and peak hours of habitual-position IOP and seated IOP were analyzed in all patients. Subgroup analysis was also performed, with groups defined by the time of maximum habitual-position IOP. The relationship between 24-hour habitual-position IOP parameters and VF indices was evaluated. There were 72 men and 105 women, all of whom were Koreans. Analysis of the entire population indicated a nocturnal peak (acrophase) for habitual-position IOP. Subgroup analysis indicated that 28 (15.8%) patients had diurnal acrophase, 91 (51.4%) patients had nocturnal acrophase, and 58 (32.8%) patients had no evident acrophase. There were no correlations between various 24-hour habitual-position IOP parameters and VF indices. In the 177 NTG patients, there was a significant nighttime elevation of habitual-position IOP, and nocturnal seated IOP was significantly less than nocturnal habitual-position IOP. Subgroup analysis indicated three distinct daily patterns of peak IOP in the patients. There was no relationship between nocturnal elevation of habitual IOP and the magnitude of VF damage.