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Editors Selection IGR 18-1
Intraocular Pressure: Repeatability of diurnal IOP patterns
Comment by Albert Khouri on:
27929 Short-term repeatability of diurnal intraocular pressure patterns in glaucomatous individuals, Realini T; Weinreb N; Wisniewski S, Ophthalmology, 2011; 118: 47-51
Intraocular pressure (IOP) remains the only modifiable risk factor for glaucoma. Regulation and behaviour of IOP is complex and poorly understood. In clinical practice it is often assumed that IOP follows a repeatable pattern. This is frequently the premise behind clinicians bringing back patients for IOP measurements during the same time of the day in an attempt to minimize inherent circadian fluctuations. Realini et al. (139) conducted a prospective well designed observational study to evaluate the short term repeatability of diurnal IOP patterns in eyes with primary open angle glaucoma. They enrolled forty seven subjects treated for glaucoma. Intraocular pressure was measured by Goldmann tonometry every two hours from eight AM and eight PM on two days one week apart.
Diurnal IOP performed on one day inadequately reflects diurnal IOP variability in the short term
Glaucoma treatment remained unchanged, and compliance was reviewed at each visit. Applanation tonometry was performed using a methodology similar to that of OHTS (with the examiner and recorder being two separate individuals) to minimize bias. Although subjects were predominantly Caucasian (91.5%), female (63.8%), and mostly on topical glaucoma treatment, it is unlikely that any of those factors influenced outcomes significantly. Subjects were monitored for compliance and were at pharmacologic steady state.
Although the between visit agreement of IOP at each time point was fair to good, the between visit agreement of IOP change over two hour time periods was uniformly poor (intraclass correlation coefficients ranging from -0.08 to 0.38 in right eyes, and -0.11 to 0.36 in left eyes). Even when longer time periods were compared (up to 12 hour periods) no repeatable diurnal IOP pattern was present.
Assessing IOP reduction after starting a glaucoma medication by checking IOP at the same time of day before and after is not supported by scientific evidence
What can we learn from this article about our clinical assumptions on IOP? Simply, diurnal IOP patterns are not repeatable in the short term in treated patients with glaucoma (of note the authors had similar findings in healthy subjects of similar age). The current study demonstrates that diurnal IOP performed on one day inadequately reflects diurnal IOP variability in the short term. For the clinician this means assessing IOP reduction after starting a glaucoma medication by checking IOP at the same time of day before and after is not supported by scientific evidence. Given the lack of a reproducible IOP diurnal pattern, confirming IOP change by multiple measurements is more accurate and less likely to be affected by diurnal variability.
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