Background: Intermittent exotropia (IXT) is a common form of childhood exotropia. Surgery is thought to be an effective method for the treatment, recession of lateral rectus (LR) muscles most frequently used. The tendon width of the LR which has been reported to be a useful indicator for estimation of the effect of LR recession in IXT. Aim : It was to determine whether the tendon width of the LR would predict the effects of lateral rectus recession. Patients and Methods: This was a prospective study included 30 patients had IXT, they were divided into two groups: group 1 (age ≤10 y), group 2 (>10 y). All of them underwent unilateral or bilateral LR recessions according to the preoperative angle of deviation, the tendon width of LR muscle was measured by surgical calipers. The actual effect of lateral recession was calculated then compared it to hypothetical effect. Results: there is statistically significant negative correlation between tendon width and actual effect in all group (r= -0.7921, P.<0.05). The actual effect was 2.60, 2.51, and 1.76PD when ranges of tendon width were 8mm, 8.5- 9mm, and 9.5-10mm, respectively. Conclusion: In our study we found the tendon width of LR muscle significantly affect surgical dose response, where the effects of LR recession were larger in cases in which the tendon width of muscle was decreased, and the effect was smaller in cases in which the tendon width of muscle was increased.