Intraocular Pressure Variability in Observation Participants in the Ocular Hypertension Treatment Study (OHTS)

Abstract

Purpose: : To determine variability of intraocular pressure (IOP) within the same eye and between both eyes in untreated participants in the Ocular Hypertension Treatment Study (OHTS).

Methods: : Of 819 participants randomized to observation, we report on 784 participants who completed a baseline visit and follow-up visits every 6 months over a 36-month period. We calculated Pearson correlation coefficients of IOP measurements between eyes of participants on each visit and within the same eye of participants between baseline and follow-up visits. We examined the impact of "regression to the mean" and diurnal variation on the correlation between baseline and 6 month IOP measurements. The effect of measurement sequence of right and left eyes was also examined.

Results: : The correlation of IOP measurements between the two eyes of a participant at each visit ranged from r=0.65 to 0.76 over the follow-up period; the correlation of IOP measurements within the same eye ranged from r=0.32 to 0.50 between baseline and follow-up visits. The IOP in the eye with the higher baseline IOP (mean 25.9±2.9 mmHg) decreased a mean of 0.7±3.6 mmHg at 6 months whereas the eye with the lower baseline IOP (mean 24.0±2.8 mmHg) remained relatively unchanged with a mean of 0.0±3.1mmHg. The correlation of IOP measured less than or equal to 2 hours vs. greater than 4 hours of the same time of day between baseline and 6 month visits were r=0.54 and r=0.33 respectively. The mean IOP of the right eye, which was measured first, was 0.2-0.4 mmHg higher than the left eye at each visit.

Clinical Trial: : www.clinicaltrials.gov NCT00000125

Keywords: intraocular pressure