To compare the visual outcomes and corneal higher-order aberrations (HOAs) of patients with high or low myopic astigmatism after small incision lenticule extraction (SMILE).

A total of 157 eyes of 157 patients who underwent SMILE were included in this retrospective, nonrandomized, comparative study. All the eyes which were with the rule astigmatism were divided into high astigmatism group (HAG; astigmatism ≤-2.00 D, 73 eyes) and low astigmatism group (LAG; astigmatism ≥-1.00 D, 84 eyes). Visual and refractive examinations were performed, HOAs of the anterior surface, posterior surface, and total cornea of the eyes were evaluated preoperatively and 6mo postoperatively.

At the postoperative 6-month follow-up, uncorrected distance visual acuity of 20/20 or better was achieved in 97% and 100% eyes in HAG and LAG respectively and 74% and 100% eyes were within -0.50 D. Vector analysis revealed no significant differences in the correction index (P=0.066), angle of error (P=0.091) or flattening index (P=0.987) between two groups. The magnitude of error was -0.37±0.31 D in HAG and -0.04±0.19 D in LAG (P<0.001). Index of success (IOS) was 0.22±0.09 in the HAG and 0.50±0.46 in the LAG (P<0.001). HOAs of most anterior, posterior and total cornea significantly increased after SMILE, especially the spherical aberration and coma. For HAG, the SMILE procedure induced significantly higher anterior, posterior and total cornea horizontal coma and total corneal total HOAs compared with LAG (P<0.001) and these surgically induced HOAs predominantly originated from the anterior surface of the cornea.

SMILE surgery induces more HOAs and a mild under-correction of astigmatism in eyes with high astigmatism. The increment in HOAs after SMILE is related to preoperative astigmatism.

To assess early visual outcomes and corneal stability following small incision lenticule extraction (SMILE) in eyes with a pre-planned residual stromal thickness (RST) ranging from 280 to 300 μm.

This retrospective study was designed to evaluate 82 eyes from 82 patients, all of whom had a pre-planned RST of 280 to 300 μm and normal corneal topography prior to undergoing SMILE surgery. The mean preoperative spherical equivalent (SE) was -4.82±1.30 D. A standard follow-up protocol was conducted between 1 to 6mo postoperatively. Visual outcomes were recorded using uncorrected visual acuity (UCVA) and subjective refraction. The curvature of the anterior and posterior corneal surfaces, as well as the posterior elevation at the thinnest point (PTE) were derived from the Pentacam system.

At the final follow-up, the efficacy index was 1.14±0.15, the safety index was 1.20±0.13. The mean preoperative UDVA was 0.78±0.16 logMAR, which improved significantly to -0.07±0.06 logMAR postoperatively (P<0.001). The preoperative mean SE was -4.82±1.30 D, which decreased to -0.14±0.30 D by the last visit. The curvature of the anterior cornea at the flat meridian (AK1) were 42.62±1.02 D preoperatively, 38.56±1.37 D and 38.59±1.39 D at 1 and 6mo after operation, respectively. Corresponding measurements at the steep meridian (AK2) were 43.55±1.14 D preoperatively, 39.18±1.46 D and 39.22±1.50 D at 1 and 6mo after operation, respectively. Both AK1 and AK2 remained stable at 1 and 6-mo postoperative intervals (P=0.126 and 0.082, respectively). There were no observed changes in the curvature of the posterior cornea at the flat meridian or at the steep meridian, or the PTE before and after surgery.

SMILE represents a safe and effective procedure for the correction of myopia and astigmatism in eyes featuring a pre-planned RST ranging from 280 to 300 μm accompanied by normal corneal topography, on the premise of strict control of surgical indications.