AIM:To evaluate visual outcomes and visual function in nonamblyopic adults with myopic anisometropia treated with small incision lenticule extraction(SMILE).METHODS:Prospective comparative cohort study. The consecutive patients who underwent SMILE for the treatment of myopia or myopic astigmatism at Zhongshan Ophthalmic Center(Guangzhou, China)between October 2015 and January 2016 were included. They were divided into two groups based on the bilateral difference of a spherical equivalent(SE)refraction ≥1.50 D: the anisometropic myopia group(interocular SE difference ≥1.50 D)and non-anisometropic myopia group(interocular SE difference<1.50 D). Refractive status, uncorrected and corrected distance visual acuity(UDVA and CDVA), and visual function parameters including fusional vergence amplitude, stereoacuity and horizontal phoria were measured preoperatively and at 1 wk,1,3 and 6 mo after surgery.RESULTS:A total of 49 cases(98 eyes)were included in the study, and 19 cases(38 eyes)in the anisometropic group, including 11 males and 8 females, with a mean age of 25.4±6.2 y, and 30 cases(60 eyes)in the non-anisometropic myopia group, including 19 males and 11 females, with a mean age of 26.8±4.6 y. The CDVA of the non-anisometropia group was significantly better than that of the anisometropia group 6 mo postoperatively(P=0.036). However, the safety and efficacy indexes of the two groups did not show significant differences. The fusional vergence(break point and recovery point)of the anisometropia group decreased(P=0.005 and P=0.03)and was significantly lower than that in the non-anisometropia group at 6 mo post operatively(P=0.029 and P=0.046). Both groups showed a significant improvement in distance and near stereopsis at 1, 3 and 6 mo in comparison with the preoperative baseline and 1 wk postoperatively(all P<0.05). No clinically significant change in the amount of ocular alignment in terms of distance and near deviation postoperatively in either groups.CONCLUSION: SMILE is a predictable, effective, and safe method for correcting myopic anisometropia in adults without amblyopia. Although the fusional vergence amplitudes changed, stereopsis can be improved after surgery.