PURPOSE: To test the hypothesis that the correlation between office-hour intraocular pressure (IOP) and peak nocturnal IOP is weakened after using a prostaglandin analog. DESIGN: Before-and-after study. METHODS: Twenty-four-hour IOP data obtained in a sleep laboratory of 51 patients (22 patients with open-angle glaucoma and 29 patients with ocular hypertension) were reviewed. Patients had no IOP-lowering medication upon study entry and were then treated with prostaglandin monotherapy for 4 weeks. Measurements of IOP were taken every 2 hours in the sitting and supine positions during the diurnal/wake period (7:30 AM-9:30 PM) and in the supine position during the nocturnal/sleep period (11:30 PM-5:30 AM). Individual and average IOP readings during office hours (9:30 AM-3:30 PM) and peak IOP during the nocturnal/sleep hours were analyzed using the Pearson correlation coefficient and linear regression. RESULTS: There were statistically significant correlations for all the paired variables for the analyses. Average office-hour IOP had a higher correlation with peak nocturnal IOP than individual office-hour IOP. After the treatment with prostaglandin analog, the correlation between average office-hour IOP and nocturnal peak IOP in the sitting position (r = 0.373) and the supine position (r = 0.386) were reduced from the sitting baseline (r = 0.517) and the supine baseline (r = 0.573) in right eyes. Similar change patterns appeared in left eyes. CONCLUSION: There is a correlation between office-hour IOP reading and peak nocturnal IOP under no IOP-lowering treatment as well as under prostaglandin monotherapy. The strength of correlation was weaker under the treatment compared with baseline.
Shiley Eye Institute, University of California, San Diego, La Jolla, Caifornia, USA; Beijing Tongren Eye Center, Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China.