neurologic disorders
Internuclear Ophthalmoplegia
One and a half syndrome
This uncommon syndrome occurs if a lesion affects the horizontal gaze center and the MLF on the same side. The eye affected by the lesion cannot move horizontally to either side, but the eye on the side opposite the lesion can abduct; convergence is unaffected. Causes of one-and-a-half syndrome include multiple sclerosis, infarction, hemorrhage, and tumor. With treatment (eg, radiation therapy for a tumor, treatment of multiple sclerosis), improvement may occur but is often limited after infarction. 