Central corneal thickness measurements in unoperated eyes and eyes after PRK for myopia using Pentacam, Orbscan II, and ultrasonic pachymetry

PURPOSE: To compare central corneal thickness measurements obtained in unoperated eyes and eyes after myopic photorefractive keratectomy (PRK) using a rotating Scheimpflug camera (Pentacam), a scanning slit corneal topography system (Orbscan II), and ultrasonic pachymetry. METHODS: Corneal thickness was measured using Pentacam, Orbscan II, and ultrasonic pachymetry in 25 unoperated eyes (unoperated group), 24 eyes 1 to 3 months after myopic PRK (early postoperative PRK group), and 21 eyes 4 months or more after myopic PRK (late postoperative PRK group). RESULTS: In the unoperated group, corneal thickness measurements were similar for all three methods (P=.125). In the early postoperative PRK group, Orbscan measurements were thinner than Pentacam and ultrasonic measurements by a mean of 69.4 μm and 63.4 μm (P<.001 and P=.002, respectively). In the late postoperative PRK group, Orbscan measurements were thinner than Pentacam measurements by a mean of 36.0 μm (P=.017). Pentacam and ultrasonic pachymetry measurements were similar for all three groups with a mean difference of approximately 10 μm. CONCLUSIONS: Following myopic PRK, Pentacam was comparable to ultrasonic pachymetry in measuring corneal thickness, whereas Orbscan measurements were thinner.