Intraocular lens(IOL)often has different degrees of tilt, decentration and rotation in the eye. The deflection of IOL is an important factor to impact on the visual quality of the patients with cataract surgeries. Vision was commonly used to evaluate visual quality before. In recent years, some new methods are also introduced to evaluate visual quality, such as optical aberration, modulation transfer function(MTF)and subjective visual perception. They show that the IOL deflection will cause decreases in eyesight and MTF, cause increase in aberration, lead to ametropia and so on. Therefore, a better evaluation of the effects of IOL deflection on visual quality, has significance for IOL selection, positioning and cataract individualized treatment.