Abstract
Purpose: :
Peak IOP is an important clinical parameter in glaucoma management. Clinical estimation of peak IOP remains a challenge given the low IOP sampling rate that occurs in routine practice. The purpose of this study was to determine the predictive value of a single supine IOP measurement on long-term peak IOP among treated glaucoma patients.
Methods: :
44 patients with treated open-angle underwent diurnal IOP assessment (mean of two readings) using Goldmann tonometry in the seated position every two hours from 0800 to 2000 on five different days (day 0, 1 week later, and 1, 6 and 12 months later). Peak IOP was defined as the highest of the 35 Goldmann values across 5 visits and 7 time points per visit throughout the year. Pneumotonometry in the supine position (measured five minutes after supine positioning) was assessed on one of the study visits (mean of two readings). Regression analysis was employed to assess the relationship between supine pneumotonometric IOP and peak Goldmann IOP. Right eye data is presented.
Results: :
Mean peak Goldmann IOP in treated glaucoma patients was 20.4 ± 3.5 mmHg and mean supine pneumotonometric IOP was 20.3 ± 4.0 mmHg. In a regression model controlling for age, sex, race and central corneal thickness, supine pneumotonometry was significantly associated with peak seated Goldmann tonometry (beta=0.43, p=0.0009). None of the control terms was significant in the model and the overall model fit yielded an r-squared of 0.32 (p=0.009).
Conclusions: :
A single supine IOP assessment during office hours measured by pneumotonometry is a statistically significant predictor of long-term peak Goldmann IOP, but IOP is an inherently variable parameter and supine IOP has limited clinical value as it does not account for the majority (68%) of the variability in peak IOP.
Keywords: intraocular pressure • circadian rhythms