Anterior segment optical coherence tomography evaluation of corneal epithelium healing time after 2 different surface ablation methods

Objectives:

To compare epithelial healing time following laser epithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) with anterior segment optic coherence tomography (AS-OCT).

Methods:

This prospective interventional case series study comprised 56 eyes of 28 patients that underwent laser refractive surgery in the Department of Ophthalmology, Medipol University Medical Faculty, Istanbul, Turkey, between March 2014 and May 2014. Each patient was randomized to have one eye operated on with PRK, and the other with LASEK. Patients were examined daily for 5 days, and epithelial healing time was assessed by using AS-OCT without removing therapeutic contact lens (TCL). Average discomfort scores were calculated from ratings obtained from questions regarding pain, photophobia, and lacrimation according to a scale of 0 (none) to 5.

Results:

The mean re-epithelialization time assessed with AS-OCT was 3.07±0.64 days in the PRK group, 3.55±0.54 days in the LASEK group, and the difference was statistically significant (p=0.03). Mean subjective discomfort score was 4.42±0.50 in the PRK eyes, and 2.85±0.44 in the LASEK eyes on the first exam day (p=0.001). The score obtained on the second (p=0.024), and third day (p=0.03) were also statistically significant. The fourth (p=0.069), and fifth days scores (p=0.1) showed no statistically significant difference between groups.

Conclusion:

The PRK showed a statistically significant shorter epithelial healing time, but had a statistically significant higher discomfort score until the postoperative fourth day compared with LASEK.Anterior segment optical coherence tomography (AS-OCT) is a valuable, non-invasive and non-contact method to evaluate anterior segment structures quantitatively. It provides high resolution images by using a long wavelength (1.310 nm) of light; it offers rapid quantitative analysis of various structures. AS-OCT has demonstrated good repeatability and reproducibility with low intra-observer and inter-observer variability.1-3 Since laser in situ keratomileusis (LASIK) was introduced in the mid-1990’s, it has become the predominant refractive surgery for the correction of myopia, hyperopia, and astigmatism.4 However, LASIK has unique risks, including problems related to corneal flap creation and iatrogenic ectasia. Despite these factors, where possible, surface ablation procedures still advised by most refractive surgeons. Photorefractive keratectomy (PRK) is one of the surface ablation procedures, performed for treat refractive errors in patients not candidates for LASIK. However, eyes with PRK have some notable adverse effects like severe pain, discomfort and prolonged visual recovery due to the process of epithelial wound healing, which usually starts on the day of surgery and may last up to 4 days after surgery. In 2003, Camellin introduced a new technique called laser-assisted sub-epithelial keratectomy (LASEK) which would minimize discomfort, speed visual recovery time and reduce the incidence of corneal haze with PRK by preserving the epithelium as a flap and replacing it following the laser treatment.5,6 Faster re-epithelialization decreases the risk factor for postoperative infections and facilitates earlier visual rehabilitation, and reduces patient discomfort. Several studies report conflicting results in epithelial healing time after LASEK versus PRK because the different methods were used. Some comparative studies about epithelial healing time have reported no benefits of LASEK over PRK. There are also some clinical studies have demonstrated controversial results.7-9 The aim of the current study is to document the healing process of the cornea after LASEK and PRK quantitatively using a non-invasive, non-contact, and a more sophisticated method AS-OCT without removing therapeutic contact lenses (TCL).