Effect of LASIK surgery can be affected by many pre-operative and intra-operative factors. The study was conducted to assess changes in visual acuity and refraction in LASIK patients and to identify factors related to the change of visual acuity and refraction. The study included 124 eyes of 60 patients. Rate of post-operative visual acuity better than 7/10 changed from 85.5 percent (1 week) to 86.3 percent (6 months). The rate of eyes with plano + or - 0.5 D ranged from 76.6 percent (1 week) to 89.5 percent (6 months). Stability of visual acuity and refraction were significantly associated with several factors: pre-operative refractiqn, corneal thickness, ablation depth and ablation time. In conclusion, pre-operative refraction, corneal thickness, and ablation time are the key factors to consider in LASIK surgery to improve the stability and refractive results.