Lenticule Decentration Following Smile By Tear Film Mark Centration Or Angle Kappa Adjustment Centration: A Randomized, Prospective, Contralateral Eye Study

To evaluate lenticule decentration following small incision lenticule extraction (SMILE) by tear film mark (TFM) centration or angle kappa adjustment (AKA) centration and compare the difference in changes in higher order aberrations (HOAs) postoperatively between both methods.

In this prospective study, totally 30 subjects (60 eyes) undergoing SMILE for the correction of myopia were included in our study. 

One eye was conducted by TFM centration method (30 eyes) and the contralateral eye was conducted by AKA centration method (30 eyes). The uncorrected distance visual acuity, corrected distance visual acuity (CDVA), subjective refraction, corneal topography and HOAs were acquired preoperatively and 1 month postoperatively. The preoperative pupillary offset was obtained and tangential topography difference map was adopted to evaluate the postoperative decentered displacement.

The total decentered displacement was 0.22±0.08 mm in the TFM group with horizontal decentered displacement of 0.02±0.15 mm and vertical decentered displacement of 0.12±0.13 mm. The total decentered displacement was 0.20±0.10 mm in the AKA group with horizontal decentered displacement of 0.06±0.13 mm and vertical decentered displacement of 0.10±0.14 mm. No significant difference in total, horizontal or vertical decentered displacement was found between both groups (all p > 0.05). The spherical aberration, vertical coma, coma and total HOAs significantly increased postoperatively in both groups (all p < 0.01). No significant difference in changes in HOAs postoperatively was found between TFM and AKA centration groups (all p > 0.05).

Both TFM and AKA centration methods showed similar decentered displacement and HOAs changes postoperatively.