Mapping TMS‑induced light flashes (phosphenes) while tracking eye movements

Study of Visual Perception Phenomena: Phosphene Mapping Induced by TMS and Its Relationship With Eye Movements

Researchers will test whether single‑pulse TMS produces brief light flashes and how eye movements change where adults with visual snow, color blindness, and healthy volunteers see those flashes.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 50 (estimated)
• Ages: 18 Years to 65 Years
• Sex: All
• Sponsor: Skolkovo Institute of Science and Technology (other)
• Locations: 1 site (Moscow)
• Trial ID: NCT07110493 on ClinicalTrials.gov

What this trial studies

Participants aged 18–65 will receive single‑pulse transcranial magnetic stimulation (TMS) to visual cortex while wearing an eye‑tracker and EEG cap and reporting where brief phosphenes appear. The study enrolls three groups: people with visual snow syndrome, people with diagnosed color vision disorders, and healthy controls. Researchers will map relationships among stimulation site, eye position, and reported phosphene location to see how gaze shifts affect perceived location. Results aim to clarify basic mechanisms of visual perception and improve methods for mapping cortical visual responses.

Who should consider this trial

Good fit: Ideal candidates are adults 18–65 with a confirmed diagnosis of visual snow syndrome, adults with a documented color vision disorder, or healthy adults without past or active neurological, psychiatric, or ophthalmological disorders.

Not a fit: People with active neurological, psychiatric, or ophthalmological conditions outside the defined groups, or those who cannot undergo or tolerate TMS, EEG, or eye‑tracking, are unlikely to receive direct benefit from participation.

Why it matters

Potential benefit: If successful, this work could improve understanding of how eye movements alter perceived visual signals and lead to better methods for mapping visual cortex responses that may inform diagnostics or rehabilitation approaches.

How similar studies have performed: Previous basic research has shown TMS can elicit phosphenes and that eye position influences perceived location, but combining TMS with simultaneous eye‑tracking and EEG across these clinical groups is relatively novel.

Eligibility criteria

Inclusion Criteria:

For the "Patients with Visual Snow Syndrome" Arm:

Confirmed diagnosis of Visual Snow Syndrome according to the International Classification of Headache Disorders, 3rd edition (ICHD-3) criteria.

Presence of persistent, dynamic, tiny dots ("visual snow") across the entire visual field.

Presence of at least one of the following additional visual symptoms:

Palinopsia (prolonged afterimages). Photophobia (hypersensitivity to light). Nyctalopia (impaired night vision). Blurred vision. Patients whose symptoms appeared after a SARS-CoV-2 viral illness may be included.

For the "Color-blind Participants" Arm:

Presence of a color perception disorder. Must have a formal diagnosis of color blindness confirmed by specific ophthalmologic tests (e.g., Ishihara, Rabkin, Justova, or Stilling polychromatic plates, or the Farnsworth-Munsell test).

For the "Healthy Controls" Arm:

Absence of any active or past neurological, psychiatric, or ophthalmological disorders.

Exclusion Criteria:

General Criteria (Applicable to all participants):

Use of psychotropic drugs. Any contraindications to Transcranial Magnetic Stimulation (TMS), such as a history of epilepsy, seizures, or metallic implants in the head.

Pregnancy.

Specific to the "Patients with Visual Snow Syndrome" Arm:

Presence of any organic abnormalities in the eyes or visual system identified during a standard ophthalmologic examination.

Presence of comorbid psychiatric disorders or other medical conditions (e.g., migraine with aura) that could explain the symptoms.

Specific to the "Color-blind Participants" Arm:

Any non-congenital cases of color blindness. Presence of concomitant visual impairments that could affect visual perception independently of color blindness, such as cataracts, glaucoma, or macular degeneration.

Presence of concomitant neurological or psychiatric diseases, such as schizophrenia, epilepsy, or mood disorders, that could affect the study results.

Where this trial is running

Moscow

• Skolkovo Institute of Science and Technology (Skoltech) — Moscow, Russia (RECRUITING)

Study contacts

• Study coordinator: Akinshin R.

Conditions: Visual Snow Syndrome, Color Blindness, Healthy Volunteer