A Morphological Study of Corneal Flap after Thin-Flap Laser-Assisted In Situ Keratomileusis by Anterior Segment Optical Coherence Tomography

Abstract

This prospective study assessed corneal flap morphology in 115 patients undergoing laser-assisted in situ keratomileusis (LASIK). Flaps were created using the Moria M2 90-μm or KM-5000D 110-μm microkeratomes. Flap thickness was measured using anterior segment optical coherence tomography at seven points in a 7-mm diameter zone 1 h, 1 day, 3 days, 1 week and 1 month after surgery. Flap accuracy, reproducibility, uniformity and changes over time were evaluated. The Moria M2 microkeratome created flaps with less accuracy in the centre than the KM-5000D microkeratome (114.06 ± 6.46 μm vs 128.39 ± 6.79 μm, respectively, at 1 week). For both microkeratomes, flap thickness varied between most of the peripheral areas and the central point. Both microkeratomes created flaps with good central predictability and reproducibility, but high variation and significant deviation from intended thickness were observed in peripheral flap thickness.

Three-dimensional LASIK flap thickness variability: topographic central, paracentral and peripheral assessment, in flaps created by a mechanical microkeratome (M2) and two different femtosecond lasers (FS60 and FS200)

“…There are two commercially available modalities for measuring flap thickness postoperatively for a more sophisticated and precise flap assessment: anterior-segment optical coherence tomography (AS-OCT)7,8 and arc-scanning high-frequency ultrasound biomicroscopy (HF-UBM),9 which is capable of reporting total corneal, epithelial, residual stroma, flap, and flap-stromal composition maps 10,11. Even though AS-OCT can distinguish the epithelium and flap interface, to the best of our knowledge, there is only one recently commercially available OCT system that can offer a whole-cornea epithelial map visualization 12.…”