To analyze the reasons of impaired vision after LASlK and explore its preventive treatment measures preliminarily.METHODS: ln this retrospective study, 175 eyes of 134 patients whose vision was decreased after LASlK were included. The constituent ratio of every reason was counted and uncorrected visual acuity ( UCVA ) between pre-treatment and post-treatment were compared by paired t-test respectively.RESULTS:The overall incidence of impaired vision after LASlK was 1. 86%. The constituent ratio of regression was 51. 43% and UCVA increased from 0. 61±0. 22 to 0. 90±0. 38 (t=8. 00, P<0. 001) after treatment. The constituent ratio of punctate corneal epithelial defect was 32. 57% and UCVA increased from 0. 60±0. 19 to 1. 20±0. 24 (t=20. 00, P<0. 001 ) after treatment. The constituent ratio of accommodative spasm was 5. 14% and UCVA increased from 0.76±0. 21 to 1. 32±0. 22 (t=8. 14, P<0. 001) after treatment. The constituent ratio of corneal flap shift and gauffer was 4% and UCVA increased from 0. 29 ± 0. 26 to 1. 24 ± 0. 28 ( t = 6. 33, P<0. 001 ) after treatment. The constituent ratio of corticosteroid - induced ocular hypertension was 4% and UCVA increased from 0. 57±0. 05 to 1. 0 ± 0. 16 ( t= 2. 53, P<0. 05 ) after treatment. The constituent ratio of fundus lesions and diffuse lamellar keratitis ( DLK) was 2. 86% and UCVA all increased by different degrees after treatment.CONCLUSlON: The reasons of impaired vision after LASlK are many and varied. These cases could recover their vision by discovery and treatment in time, and the appropriate preventive measures were essential.