 2. Secondary outcome measures A. Change in Look And Cover, then Ten seconds of Observation Scale for Exotropia LACTOSE B. Change in Newcastle Control Score NCS C. Change in Chinese intermittent exotropia questionnaire CIXTQ D. Change in near stereopsis by Preschool randot near stereoacuity E. Change in size of distant deviation angle by prism alternating cover test F. Change in size of near deviation angle by prism alternating cover test 