This retrospective study complied with the tenets of the Declaration of Helsinki and was approved by the Ethics Board of Kaohsiung Veterans General Hospital. As this was a retrospective study, written informed consent from the patients was not required. We retrospectively reviewed the clinical charts of 12 consecutive patients who presented to our hospital with traumatic displacement of their LASIK corneal flap between August 2014 and January 2019. The inclusion criteria were patients who underwent LASIK before having eye trauma with dislocation of the corneal flap, underwent flap replacement surgery, and were followed-up for at least six months. The exclusion criteria were patients with traumatic LASIK flap displacement who lost their flap, did not undergo flap replacement surgery,and were followed-up for less than six months. Of the 12 patients, two patients did not undergo replacement surgery due to extensive scarring of the flap interface, two patients were lost to follow-up within six months, and one patient lost his flap. Therefore, seven patients were included in this case series.
We recorded each patient’s baseline demographic and medical information, including sex, age, the side of the affected eye (left or right), the mechanism of eye trauma, interval between the LASIK surgery and eye trauma, and the interval between the eye trauma and corneal flap replacement. We recorded the preoperative and postoperative one, three, and six-month best-corrected visual acuity (BCVA) and postoperative one, three, and six-month refractive data, including the spherical and keratometry measurements. BCVA was measured using Snellen charts. We further recorded the ocular surface disease index (OSDI) questionnaire results, tear meniscus height (TMH), non-invasive tear breakup time (NIBUT), and corneal sensation at the last visit of all patients. For corneal sensation, we used a Cochet-Bonnet esthesiometer. NIBUT and TMH were evaluated using an IDRA® Ocular surface analyzer (SBM Sistemi, Italy).
During replacement surgery, a sterile surgical sponge was used to completely remove any surface debris, and the surface was irrigated with a balanced salt solution (BSS). The intact part of the corneal flap was demarcated and dissected from the peripheral corneal flap toward the central stromal bed. The entire corneal flap was lifted with a LASIK spatula and was then folded back at the hinge to expose the entire stromal bed. Next, the flap was flattened with a sterile surgical sponge. Debris and epithelial cells were scraped from the stromal bed and undersurface and vigorously irrigated with BSS to remove the epithelial cells and remnants that adhered to the interface. The corneal flap was then replaced and stretched by surgical sponges to avoid folds or wrinkles. In cases where the corneal flap could not evenly adhere to the stromal bed, corneal sutures with 10–0 nylon was performed. Finally, a bandage soft contact lens was placed on the cornea for protection. Postoperatively, 1% prednisolone acetate and levofloxacin antibiotic eye drops were administered every 2 h initially and then gradually tapered over the follow-up period.
We defined the primary outcome as the vision and refraction status six months postoperatively, including the spherical equivalents and astigmatism. The secondary outcomes were defined as the OSDI, corneal sensation, TMH, NIBUT of the injured eye, and the interocular discrepancy of the OSDI, corneal sensation, TMH, and NIBUT at the last visit. The follow-up intervals from the replacement surgeries to the last visit ranged from six to 58 months. We used the median follow-up interval of 30 months to divide the patients into two secondary outcome comparison groups.
For statistical analysis, the Snellen visual acuity was converted to the logarithm of the minimum angle of resolution (logMAR) visual acuity. The categorical preoperative variables considered were sex, the side of the affected eye (left or right), the use of flap sutures, and the assistance of a femtosecond laser during LASIK. Age, the interval between LASIK and trauma, and the interval between trauma and replacement surgery were considered to be continuous preoperative variables. A statistical correlation was made using the Mann-Whitney U test and the Pearson correlation test to compare the preoperative variables with the BCVA six months postoperatively. The changes in the postoperative visual acuity and refractive error were compared using the Wilcoxon signed-rank test. The patients were divided into two groups according to their follow-up interval and statistically analyzed using the Mann-Whitney U test for their corneal sensitivity, NIBUT, TMH, and OSDI results of the last visit. The data were analyzed using IBM SPSS statistical software version 20.0. A p-value of < 0.05 was considered statistically significant.