Changes in the posterior cornea after laser in situ keratomileusis and photorefractive keratectomy
Accepted 25 March 2006.
Purpose
To study the changes in posterior corneal elevation after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) using Scheimpflug topography with the Pentacam anterior segment imaging system (Oculus, Inc.).
Setting
Department of Ophthalmology, Albany Medical Center, and a private clinical practice, Albany, New York, USA.
Methods
In this prospective study, 121 consecutive myopic eyes (103 LASIK and 18 PRK) were evaluated preoperatively and postoperatively with the Pentacam to determine elevation changes in the posterior corneal surface. Changes in posterior elevation were calculated by comparing the best-fit sphere preoperatively and postoperatively to a fixed reference sphere using the central 9.0 mm preoperative cornea. Statistical and graphic analyses were performed.
Results
The 103 LASIK eyes had a mean correction of −3.76 diopters (D) and a mean ablation depth of 62.1 μm. The mean estimated residual bed thickness (RBT) (329 μm) demonstrated a mean posterior displacement of 2.64 ± 4.95 μm. The 18 PRK eyes had a mean correction of −2.69 D and a mean ablation depth of 53.2 μm. The mean estimated RBT (464 μm) had a mean posterior displacement of −0.88 ± 4.64 μm. The difference in the mean posterior corneal displacement between the LASIK and the PRK eyes was not statistically significant (P>.05, Student t test).
Conclusions
There was no statistically significant difference in posterior corneal displacement between the LASIK and PRK patients. The changes in PRK and LASIK eyes appeared to be within acceptable measurement variation. Contrary to previous reports, ectatic changes to the posterior corneal surface did not routinely occur after LASIK surgery.
From the Albany Medical College and a private clinical practice, Albany, New York, USA
Corresponding author: Joseph B. Ciolino, MD, 361 State Street, Apartment 3 Front, Albany, New York 12210, USA.
Presented at the Corneal Federated Societies Scientific Session, Chicago, Illinois, USA, October 2005.
Supported in part by an unrestricted educational grant from the Sight Society of Northeastern New York and the Albany Lions Eye Bank, Albany, New York, USA.
Neither author has a financial or proprietary interest in any material or method mentioned.
ABSTRACT