A Study of the Change in Angle Deviation under General Anesthesia in Horizontal Strabismus Patients

Kim, Sang Jin; Oh, Joon Sup; Kim, Jin Mo

Abstract

We measured the angle deviation by prism cover test before operating and by Hirschberg's method while under a surgical plane of anesthesia and studied the changes in 105 patients with uncomplicated comitant horizontal strabismus who underwent muscle surgery in the Department of Ophthalmology, Dongsan Medical Center, Keimyung University School of Medicine from June 1985 to February 1987. We excluded from the study those patients with previous muscle surgery, neurological disease, and those with mechanical restrictions of eye movement detected either by clinical examination or positive forced duction tests under general anesthesia, or both. The results were as follows: 1. Angle deviation at far was 28.7 +/- 13.8 delta in exotropia and 39.9 +/- 15.6 delta in esotropia, revealing a significantly larger angle deviation in esotropia than exotropla. 2. The change in angle deviation under general anesthesia showed a decrease in the amount of preoperative angle deviation of 15.5 +/- 12.0 delta in exotropia and 27.2 +/- 17.7 delta in esotropia, significantly more decreased in esotropia than in exotropia. The change according to sex and age was of no significance in exotropia and esotropia. 3. The relationship between the preoperative angle deviation at far(DF) and that under general anesthesia(DA) was linear and could be written as the approximate regression formula: DA=0.40DF+2.20(r=0.76). 4. The relationship between the preoperative angle deviation at far(DF) and the change in angle deviation under general anesthesia[D(A-F)] was linear and could be written as the approximate regression formula: D(A-F)=-0.60DF+2.20 (r= -0.87). The change in angle deviation under general anesthesia revealed a decrease in the amount of preoperative angle deviation both in exotropia and esotropia and, in general, the larger the preoperative angle deviation was, the greater was the change in angle deviation under general anesthesia. 5. In exotropia, the change in angle deviation under general anesthesia according to the difference between preoperative angle deviation at near and far was -14.4 +/- 11.9 delta in cases of larger angle deviation at near than far, -18.3 +/- 9.6 delta in cases of larger angle deviation at far than near, and -18.8 +/- 15.4 delta in cases of the same angle deviation at near and far, respectively, which was of no clinical significance. 6. In esotropia, the change in angle deviation under general anesthesia according to the difference between preoperative angle deviation at near and far was +26.7 +/- 14.3 delta in cases of larger angle deviation at near than far, +35.3 +/- 27.3 delta in cases of larger angle deviation at far than near, and +25.6 +/- 18.3 delta in cases of the same angle deviation at near and far, respectively, which again was of no clinical significance. Thus, our results suggest that the eye position under surgical anesthesia has a tendency to change toward the anatomical position of rest and the innervational imbalance may play a major role in the causation of horizontal strabismus. It seems to have no influence in changing the preoperative surgical plan on the basis of the change in angle deviation under general anesthesia in horizontal strabismus patients.