Case report: Extraocular muscle paresis caused by snakebite.

A 51 year-old man presented with binocular diplopia on the three days after the snakebite in the fifth finger of the right hand by an Agkistrodon blomhoffi (mamushi). In the primary position he had an exotropia and right hypertropia, which became apparent when his head was tilted to the right. From ocular angle of deviation measured by synoptophore and Hess chart test, he was diagnosed as having medial rectus muscle paresis as well as inferior oblique muscle paresis of the left eye. Elevation deficit on right gaze in the left eye had remained during three days. Our case suggested that the occurrence of subjective binocular diplopia is an important clinical sign for the onset of general abnormalities caused by snakebite.