This was a prospective, randomized, single-center study. All surgeries were performed by one surgeon. Approval from the Institutional Review Board of Medipol University was obtained for the study. Twenty-eight patients (56 eyes) participated in this study conducted at Medipol University of Medicine Eye Clinic, Istanbul, Turkey between March 2014 and May 2014. Patients were included if they were at least 18 years old, and had spherical equivalent manifest refraction between -1.00 and -5.00 diopters (D), and astigmatism less than -2.00 D, stable refraction at least 12 months before surgery, and a minimum follow-up of 3 months. No one had signs of keratoconus, uncontrolled glaucoma, untreated retinal abnormalities, or previous intraocular or corneal surgery. The exclusion criteria were; older than 40 years, diabetes, and history of herpetic keratitis, and previous intraocular, or corneal surgery, pregnancy, nursing, collagen vascular diseases, or dry eye. Pre-operative assessments included uncorrected and best corrected visual acuity, cycloplegic refraction, pachymetry with AS-OCT, examination of cornea with Orbscan and slitlamp biomicroscopic examination of both anterior and posterior segments. Tear function was assessed using a Schirmer I test and the tear film breakup time (TBUT) was determined. Soft contact lens was discontinued for a minimum of 7 days before examination and treatment. Contralateral eyes in each patient were subject to random allocation through which, PRK surgery was carried out on one eye, and LASEK was carried out for the other eye of same patient by the same surgeon. All patients agreed to participate and gave their informed consent forms after the nature of the procedure had been explained. This study was conducted according to the declaration of Helsinki and relevant laws/regulations.
All procedures were performed with the VISX Star S4 excimer laser using a standard protocol by the same surgeon. The aim of the surgery was emmetropia. Preoperatively 10% povidone-iodine was used to clean the eyelids and periocular area for 1 minute, and then the eye was washed out with 20 ml of a balanced salt solution. All treatments were performed using topical anesthesia with one drop of 0.5% proparacaine (Alcaine, S.A. Alcon-Couvreur, Puurs, Belgium). A closed-loop lid speculum is used to retract the lids of the eye to be treated, and the other eye was occluded.
A 7.0-mm optical zone marker was applied to the cornea, centered over the entrance pupil. The epithelial cell layer of the cornea was debrided with a crescent knife and then photoablation was performed on the corneal stroma. The corneal surface and entire conjunctiva were irrigated with a balanced salt solution and the excess fluid was removed with another cellulose sponge.
An alcohol solution cone (J2908, Janach, Como, Italy) with a 10 mm diameter was applied to the corneal surface, and a 20% ethyl alcohol solution diluted with distilled water was filled inside the cone and was left for approximately 40 seconds. At the end of the time a merocel sponge (Medtronic Ophthalmics Inc, Jacksonville, FL) was used to soak up the alcohol in the cone and the entire ocular surface was carefully washed off with a balanced salt solution. An epithelial microhoe (Janach J2916A) was used to detach the flap edge and then the flap was shifted as one intact sheet toward the 12:00 position using an epithelial flap peeler (Janach J2930A). After the denuded corneal surface was ablated, the epithelial flap was washed with balanced salt solution and gently repositioned with using a spatula (Janach J2920A). For all treatment groups, at the end of surgery a therapeutic contact lens (TCL) (Purevision; base curve of 8.3 mm, 0 diopter (D), diameter of 14 mm; Bausch Lomb, Rochester, NY) was fitted to the treated eye with contact lens applanator (Janach J2935) after one drop of both 0.3% ciprofloxacin and 0.1% diclofenac were instilled on the surgical site.
Postoperative Medication: All patients were examined daily during 5 days follow up. Postoperative treatment included topical diclofenac and tobramycin drops 4 times daily during the reepithelization period. A preservative-free sodium hyaluronate 0.1% drops were applied every hour during first 48 hours postoperatively and 4 times in a day for 1 month. After re-epithelialization, 0.3% tobramycin (Tobrex, Alcon-Couvreur, Puurs, Belgium) and 0.1% deksametazon (Maxidex ,Alcon-Couvreur, Puurs, Belgium) were administered four times daily for 10 days and twice in a day for 15 days.
All patients were examined every day for 5 days, then at the 10th day, and 1, and 3 months. During first 5 days, specifically epithelial healing was followed up. Epithelial wound healing was assessed using Visante OCT Anterior Segment Imaging (Carl Zeiss Meditec, Inc, Berlin, Germany) by imaging the cornea with TCL in-situ. OCT images taken immediately after surgery and then every 24 hours until complete epithelial healing had occurred. Horizontal and vertical radial images through the central cornea were obtained for each eye on central fixation position to show sections of migrating epithelial tissue. The TCLs were removed when complete epithelialization was determined. All patients were interviewed in standardized conditions with prior information to ensure valid reliable responses. Pain, photophobia, and lacrimation were each given a score from 1 to 5. Patients were asked for each complaint separately during 5 days thereafter surgery until complete healing had occurred. At the 10th day, 1 and 3 months after surgery, uncorrected and best spectacle-corrected visual acuity, manifest refraction, slit-lamp microscopy, corneal topography with Orbscan were performed by one investigator. Subepithelial stromal haze was evaluated with the slit lamp microscope using broad tangential illumination, and graded as 0 to 4+ by 2 authors at different times, and different examination rooms. In our study, each patient served as him or her own control subject.
The Statistical Package for Social Sciences software version 17 (SPSS Inc, Chicago, IL, USA) was used for statistical analysis. The normality of the distribution of each of the parameters was checked using the normal Kolmogorov-Smirnov test. Visual acuity data were converted from Snellen chart values to LogMAR notation for statistical analysis. The Mann-Whitney U test was used to compare discomfort scores and reepithelization, and chi-squared test was used postoperative uncorrected distance vision. The significance level was set to alpha = 0.95 and p<0.05 was considered significant.