Relationship of corneal percent tissue altered with visual outcome in small incision lenticule extraction surgery

We observed the effect of different modified percentage of tissue alteration (mPTA) on corneal higher-order aberrations in small incision lenticule extraction (SMILE), and explored safe threshold values of mPTA for SMILE surgery.

148 patients (270 eyes) was retrospectively analyzed and grouped into two groups based on mPTA between 24%. Mixed linear model analysis was used for preoperative and postoperative 1 week (W1), 1 month (M1), 3 months (M3), and 6 months (M6) follow-ups to compare the differences and changes in visual acuity, and corneal higher order aberrations between groups.

Both groups showed satisfactory surgical results in the postoperative follow-up, with no statistically significant difference between the groups (F = 0.06, P = 0.81), but four of the eyes in the high mPTA group showed small refractive regression in the early postoperative period. Corn-tHOA showed a noteworthy group × time interaction effect (F = 9.308, P = 0.003), and groups had different rates of change at the time of M1, M3, M6. Similarly, Corn-tCOMA intergroup comparison was statistically different (F = 3.993, P = 0.047) and the group × time interaction effect was significant (F = 7.691, P = 0.000), with a different rate at times M1, M3. And corn-tSA varied between-group comparison (F = 11.171, P = 0.001), but the group × time interaction effect was not (F = 0.615, P = 0.606).

Corneal higher-order aberrations increase after SMILE and gradually stabilized at 3 months postoperatively, which was dominated by the increase in coma and spherical aberrations, more and faster the higher-order aberrations were introduced in higher mPTA, which was mainly reflected in the variable rate of increase in corneal coma aberrations.