RESUMEN
<p><b>OBJECTIVE</b>To investigate the relationship between various factors and the undercorrection after laser in situ keratomileusis (LASIK).</p><p><b>METHODS</b>Of 1 391 eyes (696 cases), the undercorrection eyes grouped by left or right eye were analyzed by Chi-square test and logistic regression analysis based on age, sex, occupation, address, family history of myopia and all ophthalmologic examination results before and after LASIK.</p><p><b>RESULTS</b>The results of logistic regression analysis showed that the undercorrection after LASIK of both groups was related to four factors: the duration of myopia (left eye OR = 1.076, 95% CI: 1.030 - 1.124; right eye OR = 1.093, 95% CI: 1.046 - 1.142), preoperative refractive power (left eye OR = 7.799, 95% CI: 1.755 - 34.654; right eye OR = 28.823, 95% CI: 5.750 - 144.467), preoperative best corrected vision (left eye OR = 0.000, 95% CI: 0.000 - 0.262; right eye OR = 0.000, 95% CI: 0.000 - 0.144) and the corneal thickness (left eye OR = 0.976, 95% CI: 0.965 - 0.987; right eye OR = 0.975, 95% CI: 0.964 - 0.986).</p><p><b>CONCLUSION</b>Longer duration of myopia and the more refractive power seemed to be the risk factors, while the better corrected vision and the thicker thickness of cornea the protect factors of undercorrection after LASIK.</p>