AIM: To analyse the variation of horizontal deviation in the primary position after the inferior oblique muscle weakening, and to explore the effect of the inferior oblique muscle recession on horizontal deviations in primary position.

METHODS:, In the study, 30 cases in the Department of ophthalmology of our hospital from January 2014 to September 2014 underwent the inferior oblique muscle recession as the sole without horizontal muscles surgery, who were superior obliquer paralysis and V pattern strabismus with small angle of horizontal strabismus, were analyzed. Of the 30 patients, 25 had unilateral inferior oblique muscle surgery, and then 5 had bilateral surgeries.Followed up for three to six mo, all patients were received full ophthalmologic and orthoptic examinations, including measurement of the deviation in the diagnostic positions of gaze at near 33cm and at distance 6m by prism and alternate cover test, synoptophore, Titmus stereo graph examination, Worth four lighting inspection, eye movement examination, and fundus photography preoperatively and postoperatively. The changes of horizontal deviations in the primary position after procedures were investigated.

RESULT:(1)The comparison of horizontal deviation showed significant difference pre- and post-operation in the exotropia group(P=0.00). It was postoperative respectively to reduce the original in external oblique average 3.35±2.87^△ and 4.37±2.65^△.(2)The comparison of horizontal deviation showed significant difference pre-and post-operation in the esotropia group(P=0.02), and it decreased postoperatively in average 2.43±1.99^△. There was no significant difference for horizontal deviation position between pre- and post-operation(P=0.089).

CONCLUSION:The horizontal deviation in primary position, either exotropia or esotropia, will decrease after the Inferior oblique muscle recession. This change can be compensated by the gradually improving and establishing the fusion function.