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).

Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.

The term corneal dystrophy embraces a heterogenous group of bilateral genetically determined non-inflammatory corneal diseases that are restricted to the cornea.

Reduced transparency of the stroma of cornea.

Abnormal accumulation of fluid and swelling of the stroma of cornea.

Severe reduction of the ability to see. On the 6m visual acuity scale, severe reduction is defined as less than 6/60 but at least 3/60. On the 20ft visual acuity scale, severe reduction is defined as less than 20/200 but at least 20/400. On the decimal visual acuity scale, severe reduction is defined as less than 0.1 but at least 0.05.