Comparison of the Change in Tension of Lateral Rectus Muscle between Bilateral Recession of Lateral Rectus Muscle and Unilateral Recession of Lateral Rectus Muscle and Resection of Medial Rectus Muscle in Rabbit

Ahn, J W; Kim, S J; Lee, Y H

Abstract

Bilateral recession of lateral rectus muscle and recession of lateral rectus muscle and resection of medial recutus muscle of one eye are commonly used for surgical treatment of exotropia. In order to evaluate the change of the lateral rectus muscle tension after bilateral recession of lateral rectus muscle [BLR group] and unilateral recession of lateral rectus muscle and resection of medial recutus muscle [R&R group], we performed EMG [Electromyography] to the right lateral rectus muscle after bilateral recession of lateral rectus muscle in 3 rabbits and unilateral recession of lateral rectus muscle and resection of medial recutus muscle to the right eye in 3 rabbits. We performed EMG in right lateral rectus muscle before surgery, at immediate postop., and 1, 2, 4, 6, 8 weeks after surgery respectively, and used RMS [Root mean square] -quantitative value of EMG amplitude-as a measure of lateral rectus muscle tension.If we define preoperative RMS value as 100%, RMS value decreased to 90 +/-20%in the BLR group and to 92 +/-7% in the R&R group at immediate postop., and RMS value at 1, 2, 4, 6, 8 weeks after surgery were 112 +/-16, 145 +/-8, 125 +/-36, 113 +/-42, 97 +/-13%, respectively in the BLR group, and 121 +/-16, 145 +/-78, 142 +/-33, 108 +/-10, 100 +/-27% respectively in the R&R group. There was no statistical difference between two groups in all period. The above results show that resection of medial rectus muscle has no influence on the tension of recessed lateral rectus muscle tension,and as for surgical treatment of exotropia, there is no difference between bilateral recession of lateral rectus muscle and unilateral recession of lateral rectus muscle and resection of medial recutus muscle in lateral rectus muscle tension.