Effectiveness of modified inferior oblique muscle belly transposition for V-pattern exotropia combined with mild to moderate inferior oblique muscle overaction

AIM:To investigate the effectiveness of a modified inferior oblique muscle belly transposition for treatment of V-pattern exotropia combined with mild to moderate inferior oblique muscle overaction.METHODS:Thirteen cases(23 affected eyes)of V-pattern exotropia with inferior oblique muscle overaction(+or++)who underwent the modified inferior oblique muscle belly transposition procedure were retrospectively reviewed.The amount of V-pattern,grade of inferior oblique overaction,degree of vertical strabismus,abnormal head posture,and the fovea-disc angle were evaluated before and after surgery.RESULTS:The V-pattern was corrected in all cases,and the amount of V-pattern reduced by 17.85±5.13 prism diopter(PD)on average(t=16.07,P<0.001).The surgical cure rate for mild to moderate inferior oblique muscle overaction was 87.0%(20/23).The degree of the foveadisc angle has a mean reduction of 5.45°±2.87°(t=3.95,P=0.003)after surgery.The mean vertical deviation in 5 cases with a small-angle hypertropia(5.23±3.06 PD)in the primary position reduced by 3.15±1.86 PD(t=6.10,P<0.001).No serious complications were observed.CONCLUSION:The modified inferior oblique muscle belly transposition procedure can effectively treat mild to moderate inferior oblique overaction and relieve the V-pattern,which is safe and easy to perform.