Circadian Intraocular Pressure Fluctuations : Can We Really Estimate Them During Office Hours?

Purpose:To quantify the validity of estimating mean intraocular pressure (IOP) and its fluctuations when measured during office hours in comparison with 24-hr derived values. Methods:We retrospectively analysed 144 24-h IOP curves of 19 healthy adults (age: 69±4 years; F/M=10/9), 10 healthy youngs (age: 25±4 years; F/M=6/4) and 30 glaucomatous patients (age: 71±7 years; F/M=18/12). The glaucoma group included both untreated and medically treated patients (treatments: timolol, latanoprost, brimonidine, dorzolamide, fixed combination of dorzolamide and timolol). Measurements were taken at 8 pm, midnight, 4 am, 8 am, noon, and 4 pm, both at supine (Perkins handheld tonometer) and sitting (Goldmann tonometer) positions. IOP fluctuations were calculated as the mean of individual ranges. Results:During office hours (8 am, noon, 4 pm), mean IOP was slightly overestimated with respect to 24-hr (range, +(0.5-1.2) mmHg).The difference was statistically significant only for untreated glaucoma patients and for patients treated with the fixed combination of dorzolamide and timolol both in supine and sitting positions (P<0.01). IOP fluctuations during office hours were always significantly underestimated by about -(2-4) mmHg (P<0.05), regardless of body position. Conclusions:24-hr IOP fluctuations are underestimated when assessed only during office hours.