Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

A lack of strength of the proximal muscles.

Abnormally pale skin.

Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

An area of depressed vision located at the point of fixation and that interferes with central vision.

Difficulty with discriminating red and green hues.

Tritanopia is an autosomal dominant disorder of human vision characterized by a selective deficiency of blue spectral sensitivity (Weitz et al., 1992).

Progressive external ophthalmoplegia is a condition characterized by weakness of the eye muscles. The condition typically appears in adults between ages 18 and 40 and slowly worsens over time. The first sign of progressive external ophthalmoplegia is typically drooping eyelids (ptosis), which can affect one or both eyelids. As ptosis worsens, affected individuals may use the forehead muscles to try to lift the eyelids, or they may lift up their chin in order to see. Another characteristic feature of progressive external ophthalmoplegia is weakness or paralysis of the muscles that move the eye (ophthalmoplegia). Affected individuals have to turn their head to see in different directions, especially as the ophthalmoplegia worsens. People with progressive external ophthalmoplegia may also have general weakness of the muscles used for movement (myopathy), particularly those in the neck, arms, or legs. The weakness may be especially noticeable during exercise (exercise intolerance). Muscle weakness may also cause difficulty swallowing (dysphagia).\n\nWhen the muscle cells of affected individuals are stained and viewed under a microscope, these cells usually appear abnormal. These abnormal muscle cells contain an excess of cell structures called mitochondria and are known as ragged-red fibers.\n\nAlthough muscle weakness is the primary symptom of progressive external ophthalmoplegia, this condition can be accompanied by other signs and symptoms. In these instances, the condition is referred to as progressive external ophthalmoplegia plus (PEO+). Additional signs and symptoms can include hearing loss caused by nerve damage in the inner ear (sensorineural hearing loss), weakness and loss of sensation in the limbs due to nerve damage (neuropathy), impaired muscle coordination (ataxia), a pattern of movement abnormalities known as parkinsonism, and depression.\n\nProgressive external ophthalmoplegia is part of a spectrum of disorders with overlapping signs and symptoms. Similar disorders include ataxia neuropathy spectrum and Kearns-Sayre syndrome. Like progressive external ophthalmoplegia, the other conditions in this spectrum can involve weakness of the eye muscles. However, these conditions have many additional features not shared by most people with progressive external ophthalmoplegia.

Diminished clarity of vision.

A scotoma (area of diminished vision within the visual field) located between the central point of fixation and the blind spot with a roughly horizontal oval shape.

Nystagmus consisting of horizontal to-and-fro eye movements.

Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery.