Impact of Treatment Decentration on Higher-Order Aberrations after SMILE

Abstract

Purpose . To evaluate decentration following femtosecond laser small incision lenticule extraction (SMILE) and sub-Bowman keratomileusis (SBK) and its impact on higher-order aberrations (HOAs). Methods . Prospective, nonrandom, and comparison study. There were 96 eyes of 52 patients who received SMILE and 96 eyes of 49 patients who received SBK in this study. Decentration was calculated 6 months after surgery with Pentacam. HOAs and visual acuity after the surgery were examined for patients in both groups before and 6 months after surgery. Results . The mean decentration displacement in SMILE group was significantly less than SBK group (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.020</mml:mn></mml:math>). 89 eyes were decentered within 0.50 mm after SMILE and SBK. The association between vertical decentration and the induced spherical aberration was insignificant in SMILE group (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.035</mml:mn></mml:math>). There was an association between decentration and safety index, efficacy index, vertical coma, spherical aberration, and HOAs in root mean square (RMS, μ m) after SBK (all <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mi>P</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.05</mml:mn></mml:math>). No difference was found in uncorrected and corrected distance visual acuity, safety index, efficacy index, and wavefront aberrations between the two subgroups at any delimited value after SMILE (all <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>P</mml:mi><mml:mo>&gt;</mml:mo><mml:mn>0.05</mml:mn></mml:math>). Decentration exceeding 0.37 mm affected vertical coma and RMSh of SBK eyes (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.002</mml:mn></mml:math>, 0.005). Conclusion . SMILE surgery achieved more accurate centration than SBK surgery. Vertical decentration is associated with the induced spherical aberration in SMILE.