Abstract
Purpose: :
Diurnal fluctuation in intraocular pressure (IOP) has been shown to be associated with increased risk of glaucomatous field progression. We studied quantitative and qualitative patterns of the diurnal IOP curve in patients with glaucoma.
Methods: :
Seventy–eight patients (78 eyes) from the practices of two glaucoma specialists performed home tonometry with a self–tonometer. A single session consisted of self–tonometry measurements five times a day for 5 consecutive days. Each patient performed a total of three sessions separated by weeks or months. All patients had open–angle glaucoma, normal tension glaucoma, or ocular hypertension and documented IOP below 25 mm Hg and had completed the three sessions of home tonometry within 3 years. The mean and variability of diurnal IOP and each of the diurnal curves obtained using home tonometry were characterized. Correlations between mean diurnal IOP, diurnal fluctuation, and office IOP were calculated using Spearman's rank correlation. Shape of the diurnal curves was classified separately for each session according to the time of day at which peak IOP was observed.
Results: :
Patients ranged in age from 28 to 78 years; 50% were female and 5% were African–American. Mean IOP measured by self–tonometry during the first session was 18.7 mmHg. We observed close agreement between diurnal IOP and office IOP (r = 0.81 p < 0.001). Within each variable of diurnal IOP and diurnal fluctuation, there was a high correlation between a single session of home IOP measurements and three sessions (r = 0.84). Most curves (40%) showed peak IOP in the morning. Curve shape was consistent among sessions: 90% of the patients had at least two out of three curves with the same shape.
Conclusions: :
Diurnal changes in IOP are relatively consistent within an individual patient. Information on fluctuation of IOP gained from a single session was similar to that yielded from multiple sessions. This may indicate that in these well–controlled patients, even a single session of home tonometry could provide useful information to characterize fluctuation in IOP.
Keywords: intraocular pressure • circadian rhythms • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology