Abstract: Evaluation of the severity of intermittent exotropia is important to understand the progress of the disease and the determining of treatment. At present, it is mainly focus on three aspects: deviation amplitude, stereopsis and fusion control. The prism alternative cover test was routinely used to measure deviation amplitude, but sometimes the patient's maximum deviation amplitude not be obtained. By use of staring at 30 m visual markers, staring at outdoor visual markers, cover test and prism adaptation test, we tried to break the binocular fusion to get a greater degree of strabismus. Titmus stereopsis and Randot stereopsis were mainly used to measure stereopsis in clinic, but the results of the two methods were quite different, which was related to the design of stereopsis. In addition, binocular viewing glasses, measuring environment, viewing angle may affect the measurement results.Fusion control was assessed by Newcastle control score and Office control score,but both were significantly influenced by family subjectivity or patient compliance, the new LACTOSE control rating may be a more appropriate IXT control rating tool.In addition, the consistency of deviation amplitude, stereopsis and fusion control is poor, and the clinical judgment of the severity of patients also needs comprehensive consideration. Therefore, it is necessary to understand the characteristics and influencing factors of each evaluation method when interpreting the evaluation results of IXT. (Int Rev Ophthalmol, 2022,  46: 481-485)

Key words: intermittent exotropia; , stereopsis, deviaion amplitude, fusion control