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IOP measurements most consistent between different eyes at one office visit
Ophthalmology. 2009;116(4):717-724.
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IOP measurements taken in the same eye varied more between consecutive office visits than measurements taken in left and right eyes during one visit, a study showed.
"Factors affecting the variability of IOP measurement include regression to the mean, time of day and measurement order," the study authors said. "Knowledge of variability in IOP and its measurements may help clinicians establish a more accurate baseline IOP, target IOP and assessment of medication effect."
Investigators analyzed data for 810 patients participating in the Ocular Hypertension Treatment Study, a prospective, randomized clinical trial. IOP measurements were made at baseline and at subsequent 6-month intervals up to 60 months.
The correlation of IOP measurements in the same eye between visits was r = .62. The correlation of measurements between left and right eyes at the same visit was r = .72. Results showed 13% of eyes had more than 20% change in IOP between visits; 66% of eyes had a change within 3 mm Hg and 10% of eyes had more than 5 mm Hg change between visits.
IOP measurements taken within 2 hours of the same time of day between visits correlated more strongly than measurements taken more than 2 hours apart (r = .56 and r = .39, respectively), the authors said.