Peak, Fluctuation, or Mean? A Correlation Analysis of Long-term Intraocular Pressure Variation Parameters in Patients with Stable Glaucoma

Comparison between provocative test-based and long-term intraocular pressure parameters in patients with stable open-angle glaucoma

PURPOSE

To compare provocative test-based and long-term intraocular pressure variation parameters in patients with stable open-angle glaucoma.

METHODS

A prospective observational study was carried out in which stable open-angle glaucoma patients (⩾3 years of follow-up without any changes on current medical regimen) were consecutively enrolled. All patients were submitted to a water-drinking test. Long-term intraocular pressure parameters were obtained from isolated intraocular pressure measurements from each visit (⩾5 visits). We investigated the correlation and agreement between the following water-drinking test and long-term intraocular pressure parameters: mean, peak, and fluctuation. In addition, the percentage of eyes with significant intraocular pressure peaks during the water-drinking test (defined as a difference ⩾25% between water-drinking test intraocular pressure peak and mean long-term intraocular pressure) was assessed.

RESULTS

Sixty-three eyes from 63 open-angle glaucoma patients (mean age, 60.7 ± 11.8 years) were included. Mean and water-drinking test intraocular pressure peak correlated significantly with mean (r = 0.67) and maximum long-term intraocular pressure (r = 0.52), respectively (p < 0.01). The correlation between water-drinking test intraocular pressure fluctuation and long-term intraocular pressure fluctuation was not significant (p = 0.45). Limits of agreement from Bland-Altman plots exceeded the maximum allowed difference between methods (3 mm Hg) for all the intraocular pressure parameters analyzed, suggesting poor agreement between water-drinking test-derived and long-term intraocular pressure values. Overall, significant water-drinking test intraocular pressure peaks were observed in 39.7% of these eyes with stable open-angle glaucoma.

CONCLUSION

Although some water-drinking test-based and long-term intraocular pressure parameters correlate significantly, water-drinking test results may not reflect the long-term intraocular pressure profile of stable open-angle glaucoma patients, as their agreement is poor. Many of these patients may experience significant water-drinking test intraocular pressure peaks, despite long-standing stable disease and unchanged medical regimen.