Does the order of intraocular pressure measurement affect tonometry results?

Abstract

Purpose To determine whether the order of intraocular pressure (IOP) measurement affects readings, regardless of which eye is measured first. Methods Intraocular pressure was measured in 31 and 41 dogs using applanation and rebound tonometry, respectively. Initially, IOP was measured in the first (randomly chosen) eye (reading A), followed by measurement in the fellow eye (reading B), and a third (repeated) measurement in the first eye (reading C). After 15 minutes, measurements were repeated in reverse order (readings D ‐ F). Results Applanation tonometry revealed significant differences between readings A & B (15.6 ± 2.3 and 14.8 ± 2.7 mm Hg, respectively, p = .02), A & C (15.6 ± 2.3 and 14.5 ± 2.4 mm Hg, respectively, p = .002), D & E (14.5 ± 2.3 and 13.7 ± 2.1 mm Hg, respectively, p = .02), D & F (14.5 ± 2.3 and 13.9 ± 1.9 mm Hg, respectively, p = .05), and A & E (15.6 ± 2.3 and 13.7 ± 2.1 mm Hg, respectively, p = .001). Rebound tonometry yielded similar results, with additional differences between B & C (19.1 ± 3.0 and 18.2 ± 2.4 mm Hg, respectively, p = .002) and E & F (18.7 ± 3.3 and 18.2 ± 3.3 mm Hg, respectively, p = .02). Conclusions Intraocular pressure measured in the first eye, whether right or left, is higher than in the fellow eye. Repeated tonometry in the same visit could result in a significant IOP decrease, though the magnitude may not be clinically appreciable.

Intereye Differences in the Clinical Assessment of Intraocular Pressure and Ocular Biomechanics

“…Goldmann applanation tonometry is likely subject to an intereye order effect, with intraocular pressure measured higher in the first eye measured than in the second eye measured, both in healthy subjects 18 and in subjects with ocular hypertension 19 . Similar results have been reported for pneumotonometry 20 and for rebound tonometry 21 . It is unknown whether the tonometry values and the ocular biomechanical parameters of the ORA or of the CorVis ST also differ between the two eyes.…”

Effect of topical nitric oxide donors 0.03% nitroglycerin and 0.1% hydralazine on intraocular pressure in healthy canine eyes

“…Additionally, this study only monitored heart rate to investigate potential systemic side effects, while future studies could consider assessing blood pressure as well given the reported vasodilating effects of NO donors. The effect of multiple IOP readings within one visit is an additional limit to this study, as repeated tonometry within one visit could result in significant reductions in IOP, though this may not be clinically appreciable (Pe'er et al., 2021 ). This limitation is unavoidable in studies where repeated IOP measurements are required; however, ensuring that study participants receive the same number of measurements at the same frequency can reduce variability.…”