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.

Inclusion Criteria:

• Age between 18 and 80,
• Presence of pathological expansion in ATXN1 (> or equal to 39 CAG), ATXN2 (> or equal to 33 CAG) or ATXN3 (> or equal to 45 CAG) genes, responsible respectively for SCA1, SCA2 or SCA3 or a pathological expansion (>250 GAA) in the FGF14 gene responsible for SCA27B pathology,
• Sujet symptomatic (SARA greater than or equal to 4) or presymptomatic (SARA < 4).

Exclusion Criteria:

• Study-specific criteria:

  • Subjects with systemic or ophthalmological disease that could affect the retina, impair fundus examination (severe cataract, severe/decompensated diabetes), or cause visual acuity below 20/40, intraocular pressure > 20 mmHg, "cup to disc" ratio > 0. 5, or severe refractive errors
  • Subjects with extremely severe neurological impairment, with a significant impact on the ability to perform most ophthalmological examinations; for example in patients for whom sitting, even with back support and cannot be maintained. The possibility of including subjects with a severe form will be evaluated on a case-by-case basis, according to the opinion of the principal investigator and the ophthalmologist.

• General exclusion criteria relating to regulations:

  • Failure to obtain consent (adults, non-emancipated minors, persons not in a position to give consent, research carried out in emergency situations, etc.),
  • Participants who have reached the maximum amount of compensation for their participation inresearch,
  • Non-affiliation with a social security scheme,
  • Persons placed under court protection,
  • Person taking part in research.