NMOSDCopilot is a digital tool developed for the self-assessment of Neuromyelitis Optica Spectrum Disorder symptoms that impact patients' functioning and quality of life. It has been co-designed with the help of patient advocacy groups, NMOSD patients and medical experts. It includes a smartphone-based application for patients, connected to a web portal developed for healthcare professionals (HCSPs). The patient application is composed of vision, walking, cognition, and dexterity e-active tests inspired by clinical standards, as well as e-questionnaires. The HCP web portal is a desktop-based software that allows HCPs to access the results generated via the patient application and facilitates remote monitoring of patients' symptoms.

The objectives of this study are to validate the accuracy, reliability and reproducibility of the unsupervised at-home self-assessment of symptoms on the patient's smartphone versus the standard in-clinic testing, as well as to evaluate the safety of use of the tool, its usability, and satisfaction towards the patient application among NMOSD patients, and the HCP web dashboard among HCPs.

Inclusion Criteria:

• Aged over 18 years old
• NMOSD as defined by the 2015 international consensus diagnostic criteria (AQP4+ only)
• With NMOSD treatment (treatment must be unchanged since 6 months before enrollment, and 1 month for analgesics, antidepressants, neuroleptics)
• EDSS =< 7
• With no evidence of relapse in the past 3 months before enrollment
• Who have read the information sheet and signed the informed consent form
• Able to use a smartphone
• Owns a personal smartphone which version is above 13 for IOS and 8 for Android included
• Able to read language in which the mobile application is available and able to understand pictograms

Exclusion Criteria:

• Evidence of neurologic, rheumatologic or psychiatric disorder other than NMOSD, including but not limited to major head trauma, seizures or systemic medical diseases that are likely to affect cognitive, upper limb or lower limb functioning
• Pregnant and nursing women
• Person under guardianship or curatorship
• Bedridden patients or patients with a daily activity of less than 2 hours per day
• Current drugs or/and alcohol abuse that could influence performance on the tests (clinician's judgment)
• Subject has participated in another clinical study within the previous 30 days of screening or is currently participating in another study that, in the opinion of the Investigator, might interfere with the participant's full participation in the study or confound the assessment of the participant or outcome of the study.