Laser in situ keratomileusis: epidemiology and risk factors of flap folds

Abstract

AbstractPurpose Flap wrinkles can be seen in 0,2‐4% of LASIK cases. Our purpose is to evaluate flap folds through 7 femto‐second cases and make a review of the literature on the epidemiology.Methods Retrospective monocentric review of 822 eyes who had flap created with the IntraLase FS60 femtosecond laser one month follow up were included between January 2012‐January 2014 in the Ophthalmology and Refractive Surgery Unit, Percy Military Hospital. Patients had an exhaustive examination with uncorrected (UDVA) and corrected distance visual acuities, spherical equivalent and mean keratometry (Km) were compared preoperatively and postoperatively. Flap thickness were measured with SD‐OCT and optical aberrations on Zyoptix Wavefront System.Results 7 folds of 6 patients were observed (0.85% of LASIK procedures), 4 were horizontal, 1 vertical and 2 oblique. No trauma was found. All the folds involved the visual axis. Their UDVA was +0,2 logMAR (from +0,4 to 0). Mean spherical equivalent decreased from ‐4,9 D to ‐0,43 D, mean Km changed from 43 D to 39.75 D. Postoperative optical aberrations measured at 4.57 µm (+/‐ 2). Mean thickness measured to 120µm (+/‐ 8). The main causes are early trauma, flap desiccation and contraction, intraoperative misalignment, flap thinness, large photo‐ablation of myopia and cuts with microkeratome. The folds concern throughout its thickness and are the result of hyper‐hydration of proteoglycans, resulting in irregularity of Bowman's membrane and flap deformation.Conclusion Flap folds are a potentially sight‐threatening complication. Rigorous surgical technique, education and post‐operative follow‐up would reduce their frequency, identify and treat them quickly to increase visual performance.