الفهرس 
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Abstract
This prospective interventional comparative study was carried out in El-Minia University Hospital. Forty patients, 19 male and 21 female, of age more than 3 years old with horizontal strabismus seeking for surgery were recruited from the outpatient clinic of the ophthalmology department to evaluate symmetrical and asymmetrical horizontal strabismus muscle surgery as regard efficacy and postoperative lateral incomitance.
The surgery is defined as symmetric procedure if the surgery was done on the same muscle in the two eyes and the amount of surgery done between eyes did not vary by more than 0.5 mm. The surgery is defined as asymmetric in recess-resect procedures in one eye, and three horizontal muscles surgery.
All patients had alternating horizontal strabismus with the exclusion of cases with unilateral strabismus, previous strabismus surgery and non comitant (restrictive or paralytic) strabismus. Patients with amblyopia or mental disturbance were also excluded.
Patients were divided into two groups, group I included 20 patients who were operated upon using asymmetrical procedures, 10 patients were esotropic and 10 patients were exotropic. group II included 20 patients who were operated upon using symmetrical procedure, 15 patients were esotropic and 5 patients were exotropic.
All patients were fully evaluated for measurement of visual acuity, refraction, fundus examination, measurement angle of deviation and assessment of ocular motility.
All surgeries were done by a single experienced skilled consultant and the results were evaluated at one week, one month and every month for six months after surgery. Deviation of ten prism diopter or less was accepted as satisfactory result in our study.
By comparing the two groups according to primary angle of deviation, there were no statistically significance after one month (P value = 0.810), or after three months (P value = 0.055), or after six months (P value = 0.142).
By comparing the two groups according to gaze difference, there were statistically significant lateral incomitance after one month (P value = 0.038) that become statistically insignificant after three months (P value = 0.152) and after six months (P value = 0.152).
Achieving postoperative alignment ± 10 PD or (5 degree) was considered a Success while undercorrection and overcorrection was considered as postoperative angles more or less than 10 PD.
The success rate for asymmetrical group was 95% and the success rate for symmetrical group was 90% and comparison showed no statistically significant difference (P value = 0.999)
from the results of this study, it can be concluded that the asymmetrical procedure has the same efficacy and success rate of symmetrical procedure for the correction of deviation in primary gaze. The asymmetrical procedure as well as symmetrical procedure don’t produce significant lateral incomitance after surgery.
Our results support that asymmetrical procedure offers an acceptable alternative to symmetrical procedure in correction of horizontal strabismus.
Our belief is that the decision whether surgeons to go for symmetrical or asymmetrical procedures should assess the preoperative deviation in side gazes and should include considerations of the results in right and left gazes and not only in the primary gaze.