Lenticule Thickness Readout for Small Incision Lenticule Extraction Compared to Artemis Three-Dimensional Very High-Frequency Digital Ultrasound Stromal Measurements

Abstract

The accuracy of SMILE lenticule thickness was found to be higher than actual measured stromal thickness change; however, predictability for SMILE lenticule thickness appeared higher than predictability for excimer laser ablation depth. The VisuMax readout lenticule depth was found to be 8 μm thicker than the achieved stromal change. This can be partly explained by alignment errors between preoperative and postoperative scans. However, this appears to show some biomechanical changes occur after SMILE.

Investigation of Predictability and Influence factors of the Achieved Lenticule Thickness in Small Incision Lenticule Extraction

“…Previous studies have reported results similar to those in our study. Reinstein et al [8] assessed the stromal thickness in 70 eyes from 37 patients before and 3 months after SMILE surgery using Artemis high frequency digital ultrasound.…”

“…However, divergent results were reported by several comparative studies on the relationship of predicted and achieved lenticule thickness. Reinstein et al [8] speculated that the difference between the predicted and achieved lenticule thickness was a systematic difference that was similar for both low and high myopia. Zhou et al [17] also indicated that the degree of myopia had no effect on the difference between the predicted and achieved lenticule thickness.…”

“…Reinstein et al [8] detected a systematic overestimation of central lenticule thickness of approximately 8 μm. Luft et al [9] also found that the predicted lenticule thickness was thicker than the achieved lenticule thickness, especially with higher myopic correction.…”

Small-incision lenticule extraction

“…77 Diminished cumulative tension on the RSB is thought to potentially offer advantages such as avoiding refractive instability due to anterior corneal shift as well as the incidence of postoperative ectasia. Reinstein et al 78 evaluated postoperative stromal thickness variation after small-incision lenticule extraction and found a stromal augmentation of 8 mm compared with the lenticule depth measurement originally indicated by the femtosecond platform software. The authors proposed that the mechanism for the induced biomechanical change was postoperative peripheral lamellar expansion.…”

Semiautomated SD-OCT Measurements of Corneal Sublayer Thickness in Normal and Post-SMILE Eyes

“…10,11 Furthermore, it was shown that the central epithelium thickens after small incision lenticule extraction (SMILE), which is a flapless femtosecond laser-based procedure. 12,13 The mechanisms underlying these postoperative epithelial alterations are not well understood and the knowledge of potential effects on refractive outcomes is still limited. A better understanding of epithelial remodeling reactions might eventually enable clinicians to predict the epithelial response to corneal refractive surgery.…”