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Editors Selection IGR 16-4
Intraocular Pressure: IOP R versus L eye
Comment by Tony Realini on:
27789 Effect of Measurement Order Between Right and Left Eyes on Intraocular Pressure Measurement, Pekmezci M; Chang ST; Wilson BS et al., Archives of Ophthalmology, 2011; 129: 276-281
Acknowledging that several studies have demonstrated a slightly but significantly higher IOP in right versus left eyes, Pekmezci et al. (141) conducted a study to determine if the basis for this observation is truly higher IOP in right eyes or an order effect in which right eyes are typically measured first. One hundred five healthy subjects underwent bilateral IOP assessment in this crossover study with the order of eyes randomized, such that IOP was measured in Right-Left or Left-Right order first, then two weeks later in the opposite order. Interestingly, there was no difference in mean IOP between right and left eyes overall, suggesting no inherent difference in IOP between right and left eyes. Rather, they observed that the first-measured eye consistently had higher mean IOP (1.0 mmHg when right eyes were measured first; 0.6 mmHg when left eyes were measured first; p = 0.002). Also interesting was the observation that IOP was consistently lower in both eyes at visit 2 compared to visit 1 (13.9 vs 14.7 mmHg, respectively; p = 0.001).
The initial evaluation of patients with suspected glaucoma should include multiple IOP measurements at multiple visits in order to robustly characterize IOP, as an initial single IOP measurement may overestimate IOP over time
Several hypotheses were offered to explain their findings, of which my favorite was the role of anxiety and apprehension with impending tonometry, which can raise IOP, and which is dissipated acutely with uneventful measurement of the first eye and more chronically with subsequent follow-up visits. Clinical implications of this study include a caution that the initial evaluation of patients with suspected glaucoma should include multiple IOP measurements at multiple visits in order to robustly characterize IOP, as an initial single IOP measurement may overestimate IOP over time.
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