Visual snow syndrome

This article may require copy editing for grammar, style, cohesion, tone, or spelling. You can assist by editing it. (February 2024) (Learn how and when to remove this template message)

Visual snow syndrome (VSS) is an uncommon

Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches.^[10][11] The condition is typically always present and has no known cure, as viable treatments are still under research.^[12] Astigmatism, although not presumed connected to these visual disturbances, is a common comorbidity. Migraines and tinnitus are common comorbidities that are both associated with a more severe presentation of the syndrome.^[13] Temporomandibular joint dysfunction (TMJ) may also be a common comorbidity.^{[citation needed]}

The cause of the syndrome is unclear.

In addition to visual snow, many of those affected have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others.^[15]

Visual snow likely represents a clinical continuum, with different degrees of severity. The presence of comorbidities such as migraine and tinnitus is associated with a more severe presentation of visual symptoms.^[13]

Diagnosis

Visual snow syndrome is usually diagnosed with the following proposed criteria:^[16][17][13]

• Visual snow: dynamic, continuous, tiny dots observed across the entire visual field at any time of the day, regardless of lighting conditions, persisting for more than three months.
  • The dots are usually black/gray on a white background and gray/white on a black background; however, they can also be transparent, white flashing, or colored.
• Presence of at least 2 additional visual symptoms of the 4 following categories:
  • i. Palinopsia. At least 1 of the following: afterimages or trailing of moving objects.
  • ii. Enhanced
    floaters in both eyes, excessive blue field entoptic phenomenon, self-light of the eye (phosphenes), or spontaneous photopsia
    .
  • iii. Photophobia.
  • iv. Nyctalopia; impaired night vision.
• Symptoms are not consistent with typical
  migraine aura
  .
• Symptoms are not better explained by another disorder (
  ophthalmological, drug abuse
  ).
  • Normal ophthalmology tests (best-corrected
    psychotropic
    drugs.

1. Perceiving visual static, flickering, or graininess on monochrome colors, in the sky, or in darkness can be a normal phenomenon associated with neural noise, amplified in the absence of bright visual stimuli. This effect is known as the Ganzfeld Effect. In conditions of low illumination, especially in dimly lit environments, this phenomenon is related to how the eyes and the brain process visual information in insufficient lighting. The visual system becomes more sensitive to light and can amplify noise or minor changes in visual signals. It's important to note that the perception of such phenomena may vary among different individuals due to individual differences in perception and sensitivity.^{[citation needed]}
2. When the eyes are closed, visual static may be related to the first level of visual hallucination.^{[citation needed]}
3. Eye pathologies or other neurological conditions can also be a cause of visual anomalies, including the appearance of visual static or other changes in perception. Additionally, psychological disorders, such as somatic disorders, could potentially contribute to these perceptual disturbances.^{[citation needed][18][19]}

Comorbidities

Psychological side effects of visual snow can include depersonalization, derealization, depression, photophobia, and heliophobia in the individual affected.^[2]

Patients with visual "snow" have normal equivalent input noise levels and

Persisting visual snow can feature as a leading addition to a migraine complication called persistent aura without infarction,^[23] commonly referred to as persistent migraine aura (PMA). In other clinical sub-forms of migraine headache may be absent and the migraine aura may not take the typical form of the zigzagged fortification spectrum (scintillating scotoma), but manifests with a large variety of focal neurological symptoms.^[24]

Visual snow does not depend on the effect of

• In May 2015, visual snow was described as a persisting positive visual phenomenon distinct from migraine aura in a study by Schankin and Goadsby.^[28]
• In December 2020, a study^[29] found local increases in regional cerebral perfusion in patients with visual snow syndrome.
• In September 2021, two studies^[30] found white matter alterations in parts of the visual cortex and outside the visual cortex in patients with visual snow syndrome.
• In November 2023, a study^[31] revealed that glutamate and serotonin are involved in brain connectivity alterations in areas of the visual, salience, and limbic systems in VSS. Importantly, altered serotonergic connectivity is independent of migraine in VSS, and simultaneously comparable to that of migraine with aura, highlighting a shared biology between the disorders.^[32]

Treatments

It is difficult to resolve visual snow with treatment, but it is possible to reduce symptoms and improve quality of life through treatment, both of the syndrome and its comorbidities.^[4] In some studies, lamotrigine as a treatment for visual snow syndrome only showed efficiacy in 20% of patients, and in one study, patients using lamotrigine even reported worsening of symptoms.^[33]Medications that may be used include lamotrigine, acetazolamide, verapamil,^[4]clonazepam, propranolol, and sertraline^[34] but these do not always result in positive effects.^[7][3] As of 2021, two ongoing clinical trials were using transcranial magnetic stimulation and neurofeedback for visual snow.^[35][36]

A recent study in the British Journal of Ophthalmology has confirmed that common drug treatments are generally ineffective in visual snow syndrome (VSS). Vitamins and benzodiazepines, however, were shown to be beneficial in some patients and can be considered safe for this condition.^[37]

References