Comparison of central corneal thickness measurements using Pentacam and ultrasonic pachymetry in post-LASIK eyes for myopia.

PURPOSE To compare central corneal thickness (CCT) measurements obtained using the Pentacam Scheimpflug system with those obtained using DGH ultrasound pachymetry (UP) in post-laser in situ keratomileusis (LASIK) eyes for myopia. METHODS In a prospective study, measurement agreement was assessed in 143 eyes of 72 post-LASIK patients using both the Pentacam and UP at the Eye Consultants Center in Riyadh, Saudi Arabia. RESULTS The mean CCT was 522 +/- 42.2 microm with the Oculus Pentacam and 516.2 +/- 40.6 microm with UP. The Bland-Altman plot showed that the mean +/- SD for the differences between the 2 devices was 5.8 +/- 13.6 microm, with 95% confidence interval limits ranging from -20.9 microm to 32.6 microm. A test of statistical significance indicated that the mean differences of 5.8 +/- 13.6 microm differed significantly from zero (p<0.001; Wilcoxon signed-rank test), thus indicating that the Pentacam measurements tended to overestimate CCT compared with UP. Analysis of regression showed a high correlation between the values obtained with both devices (r=0.947, p<0.001). CONCLUSIONS In post-LASIK myopic eyes, although a high correlation has been shown between Pentacam and UP measurements, Pentacam tends to overestimate CCT compared to UP. Pentacam probably cannot be used interchangeably with UP in post-LASIK eyes for myopia.