Yang D, et al. - In this before-and-after study, researchers tested the assumption that the association between office-hour intraocular pressure (IOP) and peak nocturnal IOP was weakened after utilizing a prostaglandin analog. Twenty-four-hour IOP data obtained in a sleep laboratory of 51 patients have been reviewed. Using Pearson’s correlation coefficient and linear regression, individual and average IOP readings during office hours (9:30 a.m. to 3:30 p.m.) and peak IOP during the nocturnal/sleep hours were analyzed. An association was found between office-hour IOP reading and peak nocturnal IOP under no IOP-lowering treatment as well as under prostaglandin monotherapy. Under the treatment, the strength of correlation was weaker compared with the baseline.