Investigating Brain Function in People With and Without Visual Snow Syndrome Using Adaptation to Visual Stimuli

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