Asymmetry of diurnal intraocular pressure fluctuation between right and left eyes

Purpose: To evaluate diurnal curves of intraocular pressure (IOP) in the right and left eyes of non-glaucomatous patients. Methods: We measured IOP during waking hours and in habitual positions in 102 non-glaucomatous patients every 2 hr between 09.00 hr and 23.00 hr using a Goldman applanation tonometer. Individual factors and biometries were measured and associated with diurnal IOP variations. Results: There was no significant difference in IOP variation between the right and left eyes over eight time-points (repeated measure ANOVA, P = 0.995). The mean coefficient of IOP in the right and left eyes at the eight time-points ranged from 0.806 to 0.887. Forty-one (40.2%), 15 (14.7%) and five (4.9%) patients showed at least one asymmetrical IOP variation over seven time intervals at the cut-off value >= 2, >= 3 and > 3 mmHg, respectively. Mean incidence of asymmetrical IOP variation was 10.9 +/- 1.6% at >= 2 mmHg, 2.9 +/- 0.8% at >= 3 mmHg and 0.8 +/- 0.4% at > 3 mmHg. Age, differences in anterior chamber depth, lens thickness and axial length showed several significant associations with the incidence of asymmetrical IOP variation. Conclusion: Diurnal variation of IOP showed asymmetry between right and left eyes in patients without glaucoma. Ageing and differences in local ocular factors between bilateral eyes may affect the incidence of asymmetrical IOP variation.