In a prospective single-center study, 125 consecutive patients with POAG were recruited from the glaucoma unit of the Department of Ophthalmology, University Hospital Basel, Basel, Switzerland, during a 6-month period between November 1, 2004, and April 30, 2005. Excluded were patients with pseudoexfoliation, a history of trauma, pigmentary dispersion, narrow or closed iridocorneal angle, evidence of any secondary glaucoma, any type of preceding refractive surgery and corneal disease, and chronic or recurrent inflammatory eye disease (eg, scleritis or uveitis). In addition, patients with poor cooperation, poor quality of DCT readings, and unreliable measurements due to astigmatism greater than 2 diopters were also excluded. All patients underwent 5 tonometric measurements (2 GAT readings, followed by 3 DCT readings).25,26 After each GAT measurement, a rest period of 3 minutes was allowed to minimize the tonographic effects of applanation tonometry. The mean IOP reading for each measurement method was recorded. Because DCT provides a digital readout of IOP on a liquid crystal display (LCD), prior knowledge of GAT values would not affect the result and made it mandatory to perform GAT measurements first for masking reasons. The right eye was always measured first. After application of topical anesthesia to the cornea, a paper stripe impregnated with fluorescein was used to stain the precorneal tear film immediately before IOP measurement. The patient was asked to blink before measurement to ensure equal distribution. Goldmann applanation tonometry was performed using a slitlamp (Haag-Streit, Koeniz, Switzerland) with a tonometer calibrated according to the manufacturer's guidelines.18 If IOP fluctuated during the cardiac pulse cycle, GAT measurements were taken in the middle of the pulsation amplitude. Intraocular pressure readings by DCT were computed and displayed by the instrument, thereby reducing possible observer bias. Dynamic contour tonometry provides 5 different quality levels, with 1 being the best and 5 being the poorest. As recommended by the manufacturer, only measurements of quality 3 or less were evaluated and included in the study.18 In addition, CCT was measured immediately after IOP measurements using an ultrasonic pachymeter (SP-3000; Tomey Corporation, Cambridge, Mass). The mean of 5 readings within a range of ±5 μm was used for each eye for analysis.