To compare visual and refractive outcomes as well as changes in high-order aberrations in patients with 120- versus 140-µm cap thicknesses 12 months after small incision lenticule extraction. Ninety-four patients were randomized to receive small incision lenticule extraction with either a 120-µm cap thickness (n = 47) or a 140-µm cap thickness (n = 47) to treat myopia or myopic astigmatism, if not both. In an analysis of right eyes only during the 12-month follow-up period, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive outcomes, and high-order aberrations were evaluated. The distribution of patients by age and sex between the groups did not differ significantly (P = .803 and P = .680, respectively). CDVA, spherical and cylindrical refraction, and changes in total high-order aberration, spherical aberration, coma, and trefoil were similar between the groups at 6 and 12 months, postoperatively. However, UDVA was statistically significantly higher in patients with 140-μm cap thicknesses than with 120-μm cap thicknesses at 6 and 12 months postoperatively (P < .001 and P < .001, respectively). Patients with 140-µm cap thickness showed greater improvement in UDVA than ones with 120-µm cap thickness at 12-month follow-up (P = .005). Both 120- and 140-μm cap thicknesses in small incision lenticule extraction were safe and effective thicknesses for correcting myopia or myopic astigmatism. The patients with 140-μm cap thickness had better improvement in UDVA after 12-month follow-up compared to patients with 120-μm cap thickness.
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