| Abstract: | Objective: To calculate the total corneal power and the keratometric index based on actual measurements of the anterior and posterior corneal surfaces and the central corneal thickness by Pentacam and evaluate the accuracy of this keratometric index in estimating total and posterior corneal powers. Methods: This was a series case study. Four hundred and nineteen patients (a total of 419 eyes) who had undergone preoperative examination and laser in situ keratomileusis (LASIK) surgery or cataract surgery from February to October 2017 at the Xiangtan Central Hospital and Eye Hospital, Wenzhou Medical University were chosen for the study. The radius of the best-fit sphere for the anterior corneal surface (Ra) and posterior corneal surface (Rp), and central corneal thickness (CCT) were obtained. The ratio of Ra to Rp (AP ratio), anterior corneal power, posterior corneal power and keratometric index were calculated, and the total corneal power in each eye was calculated using the Gaussian optics formula. A paired-samples t-test was used to compare the difference in K values. Results: The means for Ra, Rp, Rsimk, CCT and SimK were 7.73±0.27 mm, 6.34±0.24 mm, 7.73±0.27 mm, 537±33 μm, and 43.65±1.52 D, respectively. The mean calculated AP ratio was 1.220±0.026. The mean calculated keratometric index (Ncal) was 1.328±0.001. Conclusions: The Pentacam-derived keratometric index improves the predictive accuracies of total and posterior corneal powers. |
