Spinocerebellar ataxias (SCA) are rare genetic neurological disorders. The most common forms are SCA1, SCA2 and SCA3. Another more recently identified cause of ataxia is SCA27B. These are progressive, incapacitating pathologies, with adult onset (generally between 30 and 60 years of age) and progressive involvement. They are characterized by gait instability (ataxia), coordination disorders (dysmetria) and speech disorders (dysarthria). A complex disorder may also be present, with impaired ocular motility, double vision (diplopia) and difficulties with eye movements (ophthalmoplegia). In clinical practice, investigators have observed patients with advanced forms of SCA1 or SCA3 reporting a progressive decline in visual acuity. Other recent scientific observations confirm the possible presence of additional ophthalmological damage to the retina or optic nerve in SCA1, SCA2 and SCA3 pathologies. This study is a cross-sectional study, including subjects with SCA1, SCA2 and SCA3 at different stages of the disease, including the presymptomatic stage, with a complete and systematic study of visual damage. The same study will be applied to subjects with SCA27B in order to study the presence or absence of visual impairment, and possibly compare it with those of patients with polyglutamine-expanded SCA.