Internuclear Ophthalmoplegia (INO) is a disorder of eye movements caused by a lesion in an area of the brain called the medial longitudinal fasciculus (MLF). INO is associated with jerky eye movements (nystagmus) in one eye when the other one moves outwards. It can also, but not always, cause double vision (diplopia).
Multiple sclerosis is the most common cause of internuclear ophthalmoplegia and in MS it is usually unilateral. There are other causes including cerebrovascular problems (usually in older people) and HIV infection.
Handbook of Ocular Disease Management - Internuclear Ophthalmopledia
Internuclear ophthalmoplegia (INO)