Abstract
Purpose :
Refractive corneal surface ablation is a well established procedure which has been performed on millions of subjects around the world. Though much is known about the healing characteristics of this procedure, until recently little was known about how the corneal epithelial cells form an outer protective layer after the procedure. With the advent of Epithelial Thickness Mapping Software on the Optovue Avanti OCT we are now able to measure the thickness of the corneal epithelium. The purpose of this study was to measure the changes in the epithelial layer after refractive excimer laser surface ablation up to 6 months post-operatively.
Methods :
Subjects were recruited from the population that were candidates for refractive surface ablation (LASEK) at Eye LASIK Midland in Midland, Texas, USA. Informed consent was given for both the refractive procedure and the study on the corneal epithelium thickness by Optovue OCT. Epithelial maps and refractions were perfomed pre-operatively and at 1 week, 1 month, 3 months, and 6 months post-operatively. Epithelial and stromal (all layers except epithelium) maps were measured centrally and 1.75 mm superiorly, nasally, inferiorly, and temporally from the center. Data was evaluated by Graph Pad, Prism 6.0h software. Refractive estimated powers of the corneal epithelium were calculated using the epithelial thickness in the different measurement areas to approximate surface curves.
Results :
47 eyes from 24 patients have been followed out to 6 months post-operatively. Epithelial patterns centrally and 1.75 mm nasal, inferior, temporal, and superior to the central reading all appear to follow similar patterns. At one week all readings were significantly thinner than they were pre-operatively; 0.0052, <0.0001, <0.0001, 0.0014, and 0.0004. By three months post-operatively, corneal epithelial readings in all quadrants were thicker than those pre-operatively; 0.0003, <0.0001, <0.0001, 0.0076, and <0.0001. This increased thickness remained through the end of the 6 month measurement period.
Conclusions :
As measured at 1 week and 1 month, the corneal epithelial layer after surface ablation (LASEK) is initially thinner. By 3 months post-operatively, the epithelial layer became thicker than it was pre-operatively. It is unclear at this time if this can be attributed to modified cell organization or changes in the morphology of the epithelial cells.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.