Changes in effective optical zone after small-incision lenticule extraction in high myopia

Abstract

Purpose: To evaluate the four measurement approaches on the determination of effective optical zone (EOZ) using Scheimp ug tomography after SMILE surgery in eyes with high myopia.Setting: Corneal refractive surgery conducted in eye hospital in southern China Design: A retrospective cohort study.Methods: Total 74 subjects were recruited. EOZ was measured at 3 months postoperatively using Vertex-Based total corneal refraction method (EOZ V ), pupil-based total corneal refraction method (EOZ P ), 4 mm-Ring-Based total corneal refraction method (EOZ 4 ), and axial curvature difference map (EOZ D ), and their consistencies were compared. EOZs and planned optical zone (POZ) were compared and analyzed with eccentricity, ablation degree (AD) and total corneal aberrations.Results: Mean AD was -6.87 ± 0.75 D, and eccentricity was 0.30 ± 0.17 mm. At 3 months after surgery, the mean root mean square of ΔHOA, ΔComa, ΔTrefoil and ΔSA were 0.53 ± 0.27 μm, 0.36 ± 0.20 μm, 0.01 ± 0.84 μm, and, 0.16 ± 0.14 μm respectively. EOZ V , EOZ P , EOZ 4 and EOZ D were 5.87 ± 0.44 mm, 5.85 ± 0.45 mm, 4.78 ± 0.40 mm, 5.29 ± 0.27 mm respectively, which were signi cantly smaller than POZ 6.48 ± 0.16 mm. Bland Altman plots showed a good consistency between the four EOZs. The difference between the EOZ V and EOZ P was 0.02 mm within the range of clinically acceptable difference. In addition, EOZ D was positively correlated with AD, and the eccentricity was positively correlated with ΔHOA, ΔComa and ΔSA.Conclusions: All 4 measurement approaches demonstrated the reduction of EOZs compared to POZ.