·AIM:To explore the causes and clinical effects of laser in situ keratomileusis(LASIK)for adult myopic anisometropia.·METHODS:Bilateral eyes of 104 patients with myopic anisometropia more than 2.50 diopters were divided into the high diopter group and the low diopter group,then 186 eyes were treated with LASIK.The mean refraction,the difference of binocular anisometropia,ocular axis,uncorrected visual acuity(UCVA)and best-corrected visual acuity(BCVA)were statistically analyzed before and after LASIK.·RESULTS:Six months after LASIK,UCVA was improved significantly,the difference of binocular anisometropia was significantly decreased,and BCVA was kept at the level of pre-operation or improved much better than the level of pre-operation in all cases.The high diopter group and the low diopter group had about the same corneal curvature and the significantly different ocular axis before operation.Six months after LASIK,the corneal curvature was significantly decreased and ocular axis was kept at the level of pre-operation in all cases.·CONCLUSION:The main cause of myopic anisometropia more than 2.50 diopters in adult is the difference of ocular axis between bilateral eyes.LASIK for myopic anisometropia is an effective,safe and predictable procedure.·