toreported patient who experienced the acute onset esotropia and limited adduction of the one eye immediately following excision of primary nasal pterygium.

A 61 year- old woman who noted acute onset horizontal crossed diplopia immediately following excision of primary nasal pterygiym of left eye. When seen on the first post operative day, she had 30 prism diopters of exotropia in primary position, adduction was severely limited and globe moved only to midline when adducted. Medial rectus muscle was disinserted completely from its insertion on exploration.Under great illumination condition coupled with little manipulation of tissue, medial rectus muscle was found between tenon tissues and was reattached to original insertion by absorbable suture.

patent hah no diplopia in primary position, straight eye in primary position, and full rotation of globe in adduction and abduction at last follow-up (3 months).

anatomic consideration, meticulous pterygium surgery, timely diagnosis and prompt reoperation of injured muscle are recommended for every ophthalmologic surgeon.