ABSTRACT
Posterior corneal elevation changes are keys to early diagnosis of corneal ectasia after keratorefractive surgery, so it is important to use an accurate method for measuring posterior corneal elevation. The purpose of this study is investigating posterior corneal elevation changes with Pentacam[HR] on patients underwent photorefractive keratectomy. In this clinical trial and prospective study, Pentacam was used to evaluate changes in posterior corneal elevation before and after photorefractive keratectomy in 32 eyes of 16 patients. Posterior corneal elevation defined by maximum elevation before and after surgery and posterior corneal displacement defined by maximum difference in posterior elevation before and after surgery in the central 4mm zone. SPSS for windows [version 17] was used for data analysis and Paired T test was used for statistical analysis. The mean age of patients was 25.17 +/- 7.11 years and the mean of equivalent sphere was - 3.75 +/- 1.14 diopters. After photorefractive keratectomy, mean posterior corneal displacement was - 0.84 +/- 3.53 micrometers and mean posterior corneal elevation before and after surgery was 5.38 +/- 4.12 and 4.31 +/- 5.05 micrometers respectively [p=0.108]. There was no statistically significant difference in posterior corneal elevation values between before and after photorefractive keratectomy and no case of corneal ectasia with Pentacam, that was contrary to results obtained with Orbscan in previous studies. Our study suggests that Pentacam can show more accurate values of posterior corneal elevation in comparison to Orbscan. More studies must be performed to verify our conclusion