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Editors Selection IGR 14-3
Basic Research: Diurnal IOP patterns
Comment by Fotis Topouzis on:
26328 Diurnal Intraocular Pressure Patterns are Not Repeatable in the Short Term in Healthy Individuals, Realini T; Weinreb RN; Wisniewski SR, Ophthalmology, 2010; 117: 1700-1704
In an observational cohort study of 40 non-glaucomatous subjects, Realini et al. (1137) evaluated the short-term repeatability of diurnal intraocular pressure (IOP) patterns. Specifically, subjects underwent two diurnal IOP assessment visits 1 week apart, with Goldman applanation tonometry every two hours from 8:00 am to 8:00 pm. The ICCs for between-visit agreement of IOP values ranged from 0.37 to 0.62 in right eyes and from 0.35 to 0.71 in left eyes. The ICCs for between-visit agreement of IOP change between time points ranged from -0.25 to 0.15 in right eyes and from -0.4 to 0.22 in left eyes. The authors concluded that non-glaucomatous subjects do not manifest a sustained and reproducible diurnal IOP pattern and therefore a single-day assessment of IOP incompletely characterizes the diurnal IOP pattern.
As noted by the authors, the repeatability of diurnal IOP patterns is a common assumption, rather than an evidence-based knowledge. To date, very few published data exist on the subject, while this is the first study to use Goldmann applanation tonometry, which is the gold standard for IOP measurement both in research and clinical practice. A prospective design and standardized methods for diurnal IOP assessment are among the strengths of the study.
Even a single diurnal IOP testing session may not be feasible in every clinical setting
Interestingly, based on the results of this study, between-visit agreement of IOP values at each time point was only fair to good, while between-visit agreement of IOP change between time points was uniformly poor. Therefore, the authors suggest that fully characterizing diurnal IOP variability may require more than a single diurnal testing session. This is rather discouraging in clinical practice, considering that even a single diurnal IOP testing session may not be feasible in every clinical setting. On the other hand, the results of this study are to be seriously considered in research, particularly when designing clinical trials assessing diurnal IOP. Despite the presumed repeatability of diurnal IOP patterns, the findings by Realini et al. should not be surprising. We know that even single IOP measurements may not be repeatable due to inherent limitations of Goldmann applanation tonometry and current diurnal IOP assessment is based on snapshots of IOP. Future advances in technology providing actual monitoring of diurnal IOP may overcome the current limitation in our characterization and understanding of IOP.
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