Visual Snow Syndrome

The primary symptom of visual snow syndrome includes a continuous visual disturbance, which can be exacerbated by looking at bright and dark surfaces or looking at a computer screen. Other visual symptoms include entoptic phenomena, which refer to visual disturbances that originate from within the human eye itself. Some examples of entoptic phenomena include floaters (i.e., spots that move across one’s vision); selflight of the eye (i.e., light or colored clouds seen with closed eyes); photopsia (i.e., flash-like visual phenomena with sudden onset and brief duration); and “blue field phenomenon” (i.e., perception of moving fragments against a bright background, such as the sky). Additionally, those with VSS can experience palinopsia, which refers to the continued perception of an object even after it is no longer in the visual field and can appear as if moving objects are leaving a trace behind. Photophobia (i.e., hypersensitivity, discomfort to ambient light) and nyctalopia (i.e., impaired night vision) can also be seen. Some report oculomotor deficits, namely the inability to accommodate or focus objects up close and far away, which may result in a reduction in visual acuity.  

In addition to visual symptoms, those with VSS may experience non-visual symptoms including migraines that can occur in association with the appearance or the aggravation of their VSS. Tinnitus is also common, affecting between 15% to 75% of individuals. Additional symptoms include headaches, irritability, lethargy, and difficulty concentrating. Psychiatric comorbidities such as anxiety and depression can be seen in approximately half of individuals with VSS. Additionally, fibromyalgia, postural orthostatic tachycardia syndrome (POTS), dizziness, balance problems, paresthesia, and tremor have been reported. Factors that worsen VSS include exertion from exercise, caffeine, stress, marijuana, and poor sleep quality. Symptoms of VSS can persist over years, in some cases up to eight years, and often strongly impact the quality of life.  

Visual snow syndrome is a clinical diagnosis based on individual reports of their visual and non-visual symptoms. A thorough history can be taken which includes the onset of symptoms, history of trauma or illness, illicit drug and medication use, presence of symptoms concerning for seizure, and previous tests or medications tried. A diagnostic criteria published in the International Classification of Headache Disorders 3rd edition defines individuals as having VSS if they experience VS for longer than three months. They also need to have at least two other visual symptoms including photophobia, nyctalopia, palinopsia, and enhanced/excessive entoptic phenomenon.  

Those with VSS may benefit from an ophthalmologic evaluation and a neurological evaluation to rule out underlying causes for visual disturbance including retinal detachment, papilledema, or lesions along the visual pathway. Testing may include a magnetic resonance image (MRI) of the brain, an electroencephalogram (EEG), or visual evoked potentials. An ophthalmologist may use an electroretinogram (ERG), a diagnostic test that measures the electrical activity of the retina in response to a light stimulus; test visual fields; and use optical coherence tomography (OCT) to create pictures of the back of the eye to assess for retinal disease.