AIM: To compare the changes of exotropia deviation in children with basic type of intermittent exotropia before and after monocular occlusion test.

METHODS: Prospective clinical study. A total of 258 children with basic type of intermittent exotropia who underwent strabismus correction in our hospital from July 2021 to September 2022 were selected, including 122 males and 136 females, aged from 5 to 12 years, with an average age of 8.0±3.1 years. The exotropia deviation was measured at distance(6 m)and near(33 cm)fixation by prism alternating occlusion method, and the exotropia deviation was checked again after covering the non-dominant eyes of children for 40 min.

RESULTS: Before and after the monocular occlusion test, the exotropia deviation at distance(6 m)fixation was 28.23^△±10.79^△ and 29.79^△±10.85^△, respectively(t=-0.903, P=0.368), while the exotropia deviation at near(33 cm)fixation was 33.14^△±8.89^△ and 36.90^△±10.76^△, respectively(t=-2.377, P=0.019).

CONCLUSIONS: Monocular occlusion test has a great impact on the exotropia deviation at near(33 cm)fixation in children with basic type of intermittent exotropia before surgery. It can expose the maximum exotropia deviation, reduce the rate of undercorrection after strabismus surgery, and provide a reliable surgical plan.