Researches About Reproducibility And Symmetry Of Intraocular Pressure Curves

Purpose: To assess the short-term day-to-day reproducibility of 24-hour intraocular pressure(IOP)curves in various respects in untreated primary open-angle glaucoma(POAG)and ocular hypertension(OHT)patients.Methods: 47 subjects with POAG and 34 subjects with OHT underwent IOP measurements every 2 hours in both eyes for consecutive 48 hours by a non-contact tonometer(NCT).IOP values at each time point were recorded.Mean IOP,peak IOP,time difference of peak IOP between two days and IOP fluctuation were also calculated.Intraclass correlation coefficients(ICCs)and Bland-Altman plots were used to evaluate reproducibility.Results: ICCs of the entire IOP values for a complete 24-hour curve were 0.577 and 0.561 in POAG and OHT patients,respectively.ICCs of IOP values at different time points ranged from 0.384(10am)to 0.686(4am)in POAG patients and from 0.347(6am)to 0.760(4am)in OHT patients.ICCs of mean IOP,peak IOP and IOP fluctuation were respectively 0.832,0.704,0.367 in POAG patients and 0.867,0.816 0.633 in OHT patients.Only 37.23% and 35.29% of the peak IOP time points appeared within the time difference of 2 hours in POAG and OHT patients,respectively,while 53.19% and 48.53% appeared within 4 hours in POAG and OHT patients,respectively.Conclusion: A 24-hour IOP curve in a single day is not highly reproducible in short-term and has limited use for evaluating individual IOP condition.Mean IOP and peak IOP for a 24-hour IOP curve are useful parameters in clinical follow-up,while IOP value at a certain time point,IOP fluctuation and peak IOP time point should be interpreted with caution.Purpose: To evaluate the interocular symmetry of continuous 48-hour intraocular pressure(IOP)curves between paired eyes in untreated primary open-angle glaucoma(POAG)patients with binocular symmetric visual field defects and in untreated POAG patients with monocular visual field defects.Methods: Fifteen POAG patients with binocular symmetric visual field defects,15 POAG patients with only monocular visual field defects and 15 healthy individuals underwent continuous 48-hour IOP measurements every 2 hours in both eyes with a non-contact tonometer(NCT).IOP values were corrected based on central corneal thicknesses(CCTs).Corrected IOP values of each eye at different time points were recorded.The daily corrected mean IOP,peak IOP,IOP fluctuation of each eye and time interval of daily peak IOP time points between paired eyes were calculated.The symmetry of IOP curves was assessed using repeated-measures analysis of variance(ANOVA),mixed linear modeling and the intraclass correlation coefficient(ICC).Results: The repeated-measures ANOVA found no significant differences between paired eyes for the entire series of corrected IOP values in all groups(P values from 0.549 to 0.884).The linear mixed model indicated that neither eye(left or right)(F=0.581,P=0.449)nor the presence of visual field defects(F=0.196,P=0.659)were significant factors influencing IOP discrepancy.ICCs between the corrected IOP values of paired eyes,the daily corrected mean IOPs and the peak IOPs showed good agreement(ICCs from 0.663 to 0.818)and similarity among groups.Conclusion: Continuous 48-hour IOP curves between paired eyes were mathematically symmetric in POAG patients with binocular symmetric visual field defects,POAG patients with monocular visual field defects and healthy individuals.An asymmetric IOP curve did not seem to be a necessary condition for the formation of asymmetric visual field losses in untreated POAG.