Comparing the measurement of diurnal fluctuations in intraocular pressure in the same day versus over different days in glaucoma.

PURPOSE: To compare the measurement of diurnal fluctuations in intraocular pressure (IOP) in the same day versus over different days in primary open-angle glaucoma. METHODS: Twenty-five eyes from 25 patients with primary open-angle glaucoma were submitted to a diurnal curve on the same day, 5 measurements, 2.5 hours apart, from 8:00 am to 6:00 pm. For the measurements on different days, we randomly selected one time point from the diurnal curve for each patient. All patients were then instructed to return every 3-7 days to complete all 5 measurements. The maximum, minimum, and IOP fluctuation were compared between the 2 methods. RESULTS: The IOP fluctuation (maximum-minimum) was similar when we measured the IOP on different days (5.0+/-2.6 mmHg vs 4.0+/-1.2 mmHg, p=0.08). There was no difference regarding the minimum or maximum IOP assessed in the diurnal curve or over different days. There was a high correlation for the maximum IOP (r=0.863, p<0.001) and the minimum IOP (r=0.708, p<0.001) by either method of measuring during the same day or different days, as well as for all measurements (8:00 am: r=0.718, p<0.001; 10:30 am: r=0.479, p=0.01; 1:00 pm: r=0.628, p=0.001; 3:30 pm: r=0.757, p<0.001; and 6:00 pm: r=0.910, p<0.001). CONCLUSIONS: IOP fluctuation in primary open-angle glaucoma can be assessed using IOP measures on different days, at different time points, which strongly correlate to a diurnal curve.