Abstract: Objective To assess repeatability of  corneal parameters (curvature and central thickness) obtained by Pentacam HR in Chinese normal eyes and eyes after corneal refractive surgery, and to calculate keratometric index based on parameters obtained by Pentacam HR. Design Prospective study. Participants Subjects who received examinations for corneal refractive surgery were divided in to 2 groups. In group A, 207 eyes of 207 myopic subjects who received preoperative examinations were included. In group B, 133 eyes of 67 subjects who received preoperative examinations and postoperative examinations more than 3 month after LASIK or more than 6 month after PRK were included. Method In group A, subjective refraction and Pentacam HR were performed. In group B, subjective refraction and Pentacam HR were performed preoperatively and postoperatively. Pentacam HR performed 3 times and 3 valid results were obtained for every tested eye in both groups. Main Outcome Measures Coefficient of variation(CVw), intraclass standard deviation (Sw), and intraclass correlation coefficient(ICC) were used to evaluate the repeatability of mean anterior central corneal curvature in 3 mm zone(Ra), mean posterior central corneal curvature in 3 mm zone(Rp) and central corneal thickness(CCT) in both groups. Independent samples t test was used to compare keratometric induce from virgin eyes and post LASIK/PRK eyes. Results In group A, Ra, Rp and CCT obtained by Pentacam HR were (7.780±0.235) mm, (6.341±0.225) mm and (541.67±31.79) μm, respectively; in group B, Ra, Rp and CCT obtained by Pentacam HR were (8.625±0.412) mm, (6.379±0.237) mm and (461.89±34.70) μm, respectively. All the parameters obtained in both groups had good repeatability (all the CVw<1%, and all the ICC≥0.99). The corneal refractive index calculated based on the parameters obtained by Pentacam HR were (1.3278±0.0008) in group A and(1.3227±0.0019) in group B, and the difference was statistically significant (t=34.634, P=0.000). Conclusions Mean anterior and posterior central corneal curvature in 3 mm zone and central corneal thickness obtained by Peatacam HR had good repeatability in both virgin eyes and eyes after corneal refractive surgery. The keratometric index calculated based on Pentacam HR in eye after corneal refractive surgery was smaller than that calculated in virgin eyes. (Ophthalmol CHN, 2014, 23: 308-312)

Key words: corneal refractive surgery, corneal power, keratometric index, Pentacam HR