Periodic analysis using two-way analysis of variance for the circadian rhythm of intraocular pressure in primary open angle glaucoma

Abstract

The purpose of the article is to investigate the diurnal variation of intraocular pressure (IOP) in glaucoma patients by periodic regression analyses using two-way analysis of variance (ANOVA). Seventy-two open-angle glaucoma patients participated in this study and IOP measurements were taken in this group every 2 h during waking hours. Patients were categorized based on the Glaucoma staging system (GSS) into “severe” (GSS > stage 2) and “less severe” (GSS ≤ stage 2) groups. They were also categorized into high tension (IOP ≥ 19 mmHg) and low tension (IOP < 19 mmHg) groups. Diurnal IOP curves were plotted and analyzed for all patients and for each subgroup by periodic regression analysis with two-way ANOVA. Results showed that all diurnal IOP curves from all patients and all subgroups statistically fitted periodic regression curves within a 24-h period (p < 0.0001, two-way ANOVA for all categories). It is concluded that IOP exhibits a 24-h circadian rhythm in glaucoma patients during waking hours.