Repeatability of corneal parameters with Pentacam after laser in situ keratomileusis.

ABSTRACT

AIM: To investigate the coefficient of repeatability (CR) for corneal parameters evaluated with Pentacam after laser in situ keratomileusis (LASIK) in myopic eyes. DESIGN AND SETTING: Prospective, non-interventional, non-comparative study in an institutional setup. MATERIALS AND METHODS: Forty eyes of 40 consecutive subjects who had undergone LASIK for myopia were assessed with the Scheimpflug system (Pentacam 70700 Oculus, Wetzlar Germany). The mean of five consecutive measurements of all the corneal parameters was recorded and CR was calculated as standard deviation of the difference from the mean of these repeat measurements divided by the mean response. The statistical significance of the CR was calculated for these parameters at 5% significance level. RESULTS: The best CR was observed for the periphery of the anterior corneal curvature (0.18%) and the least for the horizontal meridian of the posterior corneal curvature (1.29%). Despite being significantly different ( P < 0.001), both the measurements were highly repeatable in post-LASIK eyes. The central, apical and minimal corneal thickness had a CR of 1%, 0.78% and 0.77% respectively. These were equally repeatable ( P> 0.323). The CR of the mean radius of curvature of the anterior cornea (0.29%) was significantly better ( P < 0.001) than the posterior corneal curvature (0.57%). CONCLUSION: The CR for the post-LASIK cornea with Pentacam was the best for the anterior corneal curvature. Significantly, Pentacam has a high degree of repeatability for the posterior corneal curvature, which has a potential for early detection of keratectasia in these eyes. Post-LASIK pachymetry with Pentacam also showed excellent repeatability.