Aims: To compare supine nighttime intraocular pressure measurements with Perkins applanation tonometry to 24-h sitting intraocular pressures with Goldmann applanation tonometry.
Methods: A prospective, untreated, uncontrolled, observational cohort of qualified consecutive ocular hypertensive or primary open-angle glaucoma patients. Patients underwent sitting intraocular pressure measurements over 24-h by Goldmann and patients had their supine nighttime intraocular pressure measurements by Perkins.
Results: In 100 completed patients, the mean intraocular pressure at 1000, 2200, 0200 and 0600 hours while sitting was 22.5+/-3.7 mm Hg, and in the supine position, 23.5+/-4.3 mm Hg (P<0.001). The mean sitting Goldmann intraocular pressures across the three daytime points was 23.3+/-3.4 mm Hg and across three nighttime points was 21.5+/-4.0 mm Hg (P<0.001). In contrast, the mean daytime sitting Goldmann intraocular pressure was not different than the mean nighttime supine intraocular pressure evaluated with Perkins (22.8+/-4.4 mm Hg, P=0.07). However, only 70% of patients were within 1.0 mm Hg of the highest daytime reading for all nighttime supine and sitting intraocular pressures.
Conclusion: This study suggests that with Perkins applanation tonometry the untreated mean supine intraocular pressures are not higher at night than daytime sitting Goldmann applanation tonometry. However, the highest daytime sitting intraocular pressure measurement does not consistently predict the highest nighttime sitting or supine intraocular pressure value.