Visual snow syndrome: what it is, symptoms, causes and treatment

Visual snow syndrome (VSS) is a continuous visual disturbance. King’s College London describes it as people seeing static, flickering dots and flashing lights, in both eyes-open and eyes-closed conditions. It says it affects about 2 to 3% of the world’s population and that it can be debilitating, affecting vision, hearing, thinking, sensory processing and quality of life.

The term describes a syndrome because the static usually travels with other symptoms. A paper in Neurology, from a King’s College London-led group, says that in addition to the static, patients very often report palinopsia (images that persist after looking away), enhanced entoptic phenomena (seeing structures of the eye itself), photophobia (light sensitivity) and nyctalopia (poor night vision). It adds that visual snow is included in the appendix of the International Classification of Headache Disorders as a complication of migraine.

Importantly, the condition is not caused by damage to the eye. Moorfields describes it as a neurological condition affecting how the brain integrates what is seen.

The same Neurology paper surveyed over 1,100 people. It found an average age of 29 years, no sex prevalence in who has the condition, and that the disorder usually started in early life, with about 40% having had symptoms for as long as they could remember. The most commonly experienced static was black and white. It reports that identifying as female was associated with reporting more severe symptoms.

People often describe a mix of visual and non-visual effects. King’s College London lists impacts on vision, hearing, thinking and sensory processing. Moorfields notes it is often associated with migraine and tinnitus, and the Neurology study found these were independently associated with a more severe presentation.

The cause is not fully understood. King’s College London reports a 2023 study using brain scans from 24 patients with VSS, 25 people with migraine and 24 healthy people. It found particular differences in the activity of glutamate and serotonin networks in specific brain areas, including reduced synchronisation in glutamate networks in the anterior cingulate cortex and reduced connectivity in serotonin networks of the visual cortex and other areas. The researchers suggest this may reflect an interruption in the filtering and integration of visual information. The study was part-funded by the NIHR Maudsley Biomedical Research Centre.

The same study found reduced serotonin-network connectivity was also seen in migraine with aura, suggesting a biological link between VSS and aura. The Neurology paper concluded that visual snow does not depend on the effect of psychotropic substances on the brain, so it should not be assumed to be caused by recreational drug use.

There is no blood test or scan that confirms visual snow syndrome. The Neurology paper states that it is defined by a set of clinical criteria, which it says validate the diagnosis in a large clinical database. Moorfields describes eligibility for its research as severe visual snow diagnosed by an ophthalmologist, neurologist or neuro-ophthalmologist, which indicates the kinds of specialist who make the diagnosis.

Moorfields says patients can be referred or self-refer to its specialist for clinical assessment or suspected diagnosis. Other conditions that can cause visual disturbance need to be considered by the doctor assessing you.

King’s College London says there is no effective medication at present, and the search for treatment has been hindered by lack of knowledge about the biology of the condition. It says the 2023 findings could provide insight into potential biological targets for treatment.

A follow-up study of 40 patients found that 14 (35%) tried treatment or lifestyle modifications for visual snow, and that in 7 of them the syndrome was ameliorated somewhat; among medicines, the study reported that magnesium, cinnarizine and flunarizine had been beneficial for some. It is a small study in selected patients and does not establish a treatment.

Moorfields and Guy’s and St Thomas’ NHS Foundation Trusts are running a study led by neurologist and neuro-ophthalmologist Dr Sui Wong examining mindfulness-based cognitive therapy for visual snow syndrome. It builds on an earlier feasibility study in which participants reported improvements to their vision, reflected in functional MRI scans. Moorfields says people with severe visual snow can apply to take part.

The follow-up study re-contacted 40 patients after a mean of about seven years and reported that symptoms had persisted in all of them. Visual snow itself was less frequently rated the most disturbing symptom, while enhanced entoptic phenomena were more often the main complaint. Three patients (7%) developed new visual migraine aura without headache. Anxiety and depression scores did not differ between visits.

These findings are from specialist clinic cohorts rather than the general population, so they may not describe everyone. If the condition is affecting daily life, mood or sleep, it is worth discussing with a GP or the specialist team.

No NHS condition page for visual snow syndrome was available when this guide was prepared, so the information here comes from NHS hospital research summaries and university research. Moorfields says patients can be referred or self-refer to its specialist for clinical assessment.

In general terms, a GP or optometrist can refer to neurology or ophthalmology on the NHS, and private neuro-ophthalmology consultations are available too. In both cases the diagnosis rests on the same clinical assessment.