Anatomic variation of the inferior oblique mucle: a potential caue of failed inferior oblique weakening urgery Original Reearch Article

PURPOE: To document the variation in normal anatomy that occur at the inertion of the inferior oblique mucle and in the vicinity of it urgical capture ite (10 to 12 mm from the inertion). METHOD: One hundred intact cadaver orbit with no hitory of eye mucle or orbital diorder during life were carefully diected to expoe the entire length of the inferior oblique mucle. The number of diviion of mucle at the inertion, total width of the mucle belly, and variation in anatomy 10 and 12 mm from the inertion were recorded. REULT: eventeen (17%) of the 100 inferior oblique mucle had multiple diviion at the inertion. Eight mucle (8%) had two bellie at 10 or 12 mm from the inertion. Among thee eight, four had two ditinct (bifid) bellie extending to the inertion, and four had dehicence in the mucle. The mean mucle width among thee eight pecimen wa 0.5 and 0.7 mm larger than the mean width of the other 92 pecimen at the 10 mm and 12 mm poition, repectively. Neither difference wa ignificant at the .05 level. CONCLUION: Multiple inertion were found in 17% of inferior oblique mucle examined; duplication of the inferior oblique mucle at the urgical capture ite were found in 8%. Thee duplication may account for ome cae of recurrence or peritence of inferior oblique overaction after weakening urgery, owing to inadvertent incomplete capture of the mucle during urgery.