Scientists scan brains to uncover the mystery of visual snow

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria 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 Exclusion Criteria 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