Measurement of central corneal thickness in myopic eyes with ultrasound and Pentacam scheimpflug system

Objective To assess the accuracy and variability of central corneal thickness measurements in myopic eyes obtained by ultrasound pachymetry and the Pentacam scheimpflug imaging system. Methods First, corneal thickness in 50 healthy eyes was measured three times with the Pentacam system to evaluate the repeatability. Then, Scheimplug imaging system (Pentacam) and A-scan ultrasonic pachymeter (SP-3000) were used to measure the corneal thickness on 217 myopic cases (433 eyes) undergoing laser in situ keratomileusis (LASIK) and 63 cases (126 eyes) 6 months after LASIK. The results were compared. Results Repeated-measures ANOVA showed the repeatability of the Pentacam measurements was high ( P0.05). Pre-operatively, the value of corneal central thickness measured by ultrasonic pachymetry and the Pentacam system was (537.26±31.61) μm and (538.08±32.72) μm, respectively. There was no significant difference between the results of these two methods (t=1.867, P0.05). The difference between these two methods ranged-35-34 μm, and was within-20-20 μm in 95.38% cases. Post-operatively, the value of corneal central thickness measured by ultrasonic pachymetry and the Pentacam system was(464.21±41.04)μm and(465.17±42.65)μm, respectively. There was no significant difference between these two methods, too (t=0.913, P0.05). There was a significant linear correlation between the two methods(P0.001). The thinnest point of cornea was mostly located surrounding the apex and inclined towards inferotemporal. Conclusion The Pentacam scheimpflug system offers an acceptable method for evaluating corneal pachymetry, which is useful in corneal refractive surgery.