 This pilot study is designed specifically to determine the short-term effect of OBVAT on intermittent exotropia in terms of 4 key areas Standardizing reported outcomes of surgery for intermittent exotropia: control score, alignment, near stereoacuity and quality of life score. Result of this pilot study will be used to determine whether a full-scale RCT should be conducted to evaluate the short and long term effectiveness of OBVAT. 