Effect of Wavefront Aberrations on Night Vision Problems and Mesopic Contrast Threshold After SMILE

PURPOSE: To investigate the effect of wavefront aberrations on night vision problems and mesopic contrast threshold after small incision lenticule extraction (SMILE). METHODS: Forty-two participants (84 eyes) who underwent SMILE were included in this prospective observational study. Visual outcomes including uncorrected distance visual acuity (UDVA), subjective manifest refraction, mesopic contrast threshold (Binoptometer 4P; Oculus Optikgeräte GmbH), and higher order aberrations (HOAs) were analyzed before and 3 months after surgery. The patient's night vision satisfaction was assessed using a questionnaire. RESULTS: The mean spherical equivalent was −5.30 ± 1.38 diopters (D) preoperatively and −0.06 ± 0.15 D postoperatively. UDVA was better than 20/20 in 98.81% of the patients and better than 20/25 in all patients. Scores of night vision satisfaction and glare changed significantly in the postoperative period ( F = 8.463, P = .001; F = 69.518, P < .001, respectively). Preoperative spherical diopters (lower order aberrations) were positively correlated with night vision satisfaction ( r = −0.329, P = .041) and glare score ( r =−0.332, P = .039). Age (odds ratio [OR] = 1.272, 95% CI = 1.019 to 1.589) and preoperative spherical diopter (OR = 0.437, 95% CI = 0.199 to 0.975) were correlated with night vision satisfaction scores by analysis of binary regression. The root mean square value of total HOAs increased 3 months after surgery ( t = −6.873, P < .001) with an increase in horizontal coma (Z 3 1 ) and spherical aberration (Z 4 0 ) ( P < .001). No correlation was observed between glare score and HOAs; however, patients with higher preoperative myopia demonstrated continuously decreasing contrast under mesopic conditions and higher postoperative horizontal coma. CONCLUSIONS: Myopic patients with higher preoperative spherical errors experienced more glare at night after SMILE surgery. Postoperative horizontal coma was associated with worse mesopic contrast thresholds. [ J Refract Surg . 2021;37(7):446–452.]