Evaluating microkeratome efficacy by 3D corneal lamellar flap thickness accuracy and reproducibility using Artemis VHF digital ultrasound arc-scanning

PURPOSE: To present a method that determines the efficacy of flap creation using a microkeratome. METHODS: Thirty-six eyes of 18 patients were included in the study, operated by two experienced surgeons using the Moria LSK-One microkeratome. Very high-frequency (VHF) digital ultrasound arc-scanning using Artemis technology was used to measure the Reinstein Flap Thickness Profile created by addition of the preoperative epithelial thickness profile to the postoperative stromal component of the flap. Descriptive statistics revealed central flap thickness accuracy and reproducibility. Univariate and multivariate regression analysis was used to determine correlations between central flap thickness and preoperative clinical parameters. Three-dimensional flap thickness maps demonstrated the mean, median, standard deviation, and range of thickness. RESULTS: Intended flap thickness was 160 μm. Mean central flap thickness was 161 μm the right eye and 166 μm the left eye. Central reproducibility (standard deviation of the mean) was 30.3 μm, with a range of 106 to 228 μm. Central flap thickness correlated to preoperative corneal thickness measured by VHF digital ultrasound but not by Orbscan. On qualitative analysis, no consistency among eyes was observed in the three-dimensional flap thickness map. Flaps were on average thinner in the center, but not in all cases. CONCLUSIONS: A systematic qualitative and quantitative statistical evaluation of microkeratome accuracy and reproducibility can be performed by measuring corneal flap thickness with arc-scanning VHF digital ultrasound.