Internuclear Ophthalmoplegia (INO) refers to a neurological disorder that affects the eye movements of a person. This condition can result in horizontal gaze palsy in one or both eyes, double vision, and an inability to move the eyes in a particular direction. Several synonyms and alternate terms are used to describe this condition, including Gaze Palsy, Ipsilateral Adduction Weakness, Medial Longitudinal Fasciculus Syndrome, and One-and-a-Half Syndrome. Additionally, these terms are used by neurologists and ophthalmologists to better describe the type and location of the lesions that result in INO, and to adjust the treatment plans for patients. However, all of these terms are indicative of the same clinical pattern observed in patients with INO.