Distribution of peak intraocular pressure in 24-hour and correlation between peak nocturnal intraocular pressure with diurnal intraocular pressure level in primary open angle glaucoma patients

Abstract

To study the distribution of peak intraocular pressure (IOP) in 24-hour in untreated primary open angle glaucoma (POAG) patients, and to explore the correlation between nocturnal peak IOP and office hour or diurnal IOP level. A Cross-sectional study.One hundred and twenty-one untreated POAG patients (121 eyes), including 78 normal tension patients (78 eyes) and 43 hyper-tension patients (43 eyes), were enrolled in this study. All the patients underwent 24-hour IOP monitoring with non-contact tonometer. The distribution of peak IOP in 24-hour and the correlation between nocturnal peak IOP and office hour or diurnal mean and peak IOP were evaluated. Categorical variables were described as frequency and constituent ratio, and analyzed by chi-square test. Continuous variables were described as mean, standard deviation, range, and analyzed by independent samples t test, pearson correlation test and linear regression. In all glaucoma patients, peak IOP occurred mainly from 8:00 to 10:00 and 8:00 to 10:00.In normal tension group, peak IOP appeared mainly from 8:00 to 10:00 and from 0:00 to 6:00, the highest frequency showed at 8:00 (17 eyes 18.48%).In hyper-tension group, the probability of IOP reaching peak was more in night time, mainly from 0:00 to 6:00, the highest frequency showed at 2:00 (10 eyes 21.28%). If only the peak IOP during office hours or diurnal hours were considered, then only 32.55% (14/43) and 44.19% (19/43) patients could be correctly diagnosed. The remaining patients would be missed because of low IOP and/or mild structure and/or functional damages. There were good linear correlations between office hours or diurnal peak and mean IOP and nocturnal peak IOP in glaucoma patients. More than 50% peak IOP occurred out of office hour in POAG patients. There is a good correlation between peak nocturnal IOP and office hour or diurnal IOP level.