Trials Today

for People with Visual Snow Syndrome: - Between the ages of 18 and 60 years old - Normal (20/25 or better in each eye) or corrected-to-normal vision (MR-compatible glasses will be provided as needed) - Ability to comply with study instructions - Individuals who have a current diagnosis of VSS from a neuro-ophthalmologist or meet diagnostic criteria of VSS (experience of dynamic dots across the visual field persisting longer than 3 months and at least 2 of the following additional visual symptoms: palinopsia, entoptic phenomena, trails behind moving objects, photophobia, or nyctalopia) - Individuals living in Minnesota within 2 hours of the study site Inclusion Criteria for Non-snow Controls: - Between the ages of 18 and 60 years old - Normal (20/25 or better in each eye) or corrected-to-normal vision (MR-compatible glasses will be provided as needed) - Ability to comply with study instructions - Individuals living in Minnesota within 2 hours of the study site

for People with Visual Snow Syndrome: - Not being fluent in English or another language for which interpretation/translation services are available - A diagnosed or self-reported intellectual disability - Current substance dependence (besides nicotine), or drug dependence with tolerance or withdrawal within past 12 months - Hallucinogenic substance use within the past 12 months or hallucinogenic substance use within 12 months prior to onset of VSS symptoms - Severe central nervous system disease - Head injury with skull fracture or loss of consciousness for more than thirty minutes - Presence of a physical problem that would render study measures difficult or impossible to administer or interpret (e.g., visual field loss) - Age less than 18 years or greater than 60 years - MRI exclusions (for MR visits only): - Metal in the body that cannot be approved by the CMRR safety committee - Pregnancy - Conditions that affect neuro-hemodynamic coupling - Claustrophobia - Inability to lie still for at least an hour - Weight in excess of 440 lbs - CT scan exclusion only: Research-related radiation exposure within the last 12 months - Any vision anomaly aside from VS or refractive error (e.g., strabismus/ crossed eyes, lazy eyes, color blindness) - Current psychotic episode Exclusion Criteria for Non-snow Controls: - Not being fluent in English or another language for which interpretation/translation services are available - A diagnosed or self-reported intellectual disability - Current substance dependence (besides nicotine), or drug dependence with tolerance or withdrawal within past 12 months - Hallucinogenic substance use within the past 12 months - Severe central nervous system disease - Head injury with skull fracture or loss of consciousness for more than thirty minutes - Presence of a physical problem that would render study measures difficult or impossible to administer or interpret (e.g., visual field loss) - Age less than 18 years or greater than 60 years - MRI exclusions (for MR visits only): - Metal in the body that cannot be approved by the CMRR safety committee - Pregnancy - Conditions that affect neuro-hemodynamic coupling - Claustrophobia - Inability to lie still for at least an hour - Weight in excess of 440 lbs - CT scan exclusion only: Research-related radiation exposure within the last 12 months - Any vision anomaly or refractive error (e.g. strabismus/ crossed eyes, lazy eyes, color blind) - A personal history of VSS symptoms or a diagnosis with VSS - Current psychotic episode