Enrolled in this study were patients with PDS who had IOPs of greater than 20 mm Hg at screening (PDS-OHT group, 17 eyes), PDS and no previous record of IOPs greater than 20 mm Hg (PDS-ONT group, 18 eyes), age-matched healthy volunteers with no ocular abnormalities and no record of IOP of greater than 20 mm Hg (ONT group, 18 eyes), and age-matched healthy volunteers with no ocular abnormalities and with at least 2 previous records of IOP of greater than 20 mm Hg on 2 separate visits (OHT group, 18 eyes). On the screening day, participants underwent an eye examination by an experienced glaucoma specialist (C.B.C.). Visual acuity was measured in both eyes. Intraocular pressures were measured with the use of a pneumatonometer (Model 30 Classic; Reichert Ophthalmic Instruments, Depew, New York). A slitlamp examination of the anterior segment was performed, and the presence or absence of PDS was determined. Gonioscopy was performed, and the average of the superior, inferior, nasal, and temporal chamber angles was determined, with 0 being closed and 4 being wide open.23 Finally, the eyes were dilated and a fundus examination was performed. Excluded from all groups were patients with visual field defects, glaucoma, ocular infection, and a history of inflammation, previous intraocular surgery, laser treatment, ocular trauma, ocular abnormality precluding fluorophotometric measurements, or unstable cardiovascular or pulmonary disease. Study participants in the PDS-OHT and OHT groups who had been taking medication to treat the elevated IOP discontinued treatment for 3 to 6 weeks before the study. The washout period depended on the prescribed ocular medication. The washout was necessary to eliminate any confounding effect of the ocular medication on IOP and aqueous humor dynamics. All participants provided informed consent following federal guidelines, and the study was approved by the University of Nebraska Medical Center institutional review board.