•Background and study aims : The investigators conducted this study to evaluate the movement of extraocular muscle after strabismus surgery with non-invasive tool called AS-OCT.

• Who can participate? patients who underwent typical lateral rectus recession surgery for correcting intermittent exotropia
• What does the study involve? Volunteers will attend a clinic for four visits over six months. They will undergo AS-OCT at every visits during follow up period. AS-OCT is non-invasive test to evaluate operation site. The test only requires their cooperation when they undergo AS-OCT.
• What are the possible benefits and risks of participating? This is non-invasive test for your postoperative follow up. Therefore, there will be no risks about this test.
• Where is the study run from? Samsung Medical Center
• When is the study starting and how long is it expected to run for? From Feb 2014 to Dec 2014

The aim of this study is 1) to evaluate the reliability and accuracy of AS-OCT in the measurement of the lateral rectus (LR) insertion distance, 2)to investigate the longitudinal change of LR muscle insertion after strabismus surgery, and 3)to determine the effect of insertion movement on the angle of deviation after strabismus surgery. An AS-OCT scan of the LR muscle was performed every visits. Preoperative limbus-LR insertion distance was compared with intraoperative surgical caliper measurement of LR insertion using intraclass correlation coefficient analysis (ICC). Data on gender, age, degree of deviation (prism diopter), and spur-LR insertion distance using AS-OCT were collected at postoperative months 1,3 6.

Inclusion Criteria:

• patients who underwent lateral rectus recession surgery for correcting intermittent exotropia

Exclusion Criteria:

• previous ocular surgery
• other ocular diseases except intermittent exotropia
• amblyopia

30 patients : 21 males and 9 females age: 9 to 60 years