Breakthrough In Diagnosing VSS

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What Is The Visual Snow Diagnosis Research About?

  • Visual snow syndrome (VSS) is a syndrome because many visual and non-visual symptoms range from tolerable to life-altering.
  • It is a misdiagnosed neurological condition since visual snow diagnosis is complex.
  • Also, the cause, area of the brain affected, or how to treat visual snow syndrome is unknown
  • In addition, the hallmark symptom is that people with VSS see the world through an overlay of moving dots throughout their entire field of vision. 
  • Besides, people with VSS experience these symptoms all the time, every day, irrespective of whether their eyes are open or closed.
  • Indeed, a diverse range of visual symptoms suggests that a unique processing error may cause the syndrome as the brain relays visual information.
  • Studying the precise point in which visual processing is affected in the brain can help us understand the condition and hence, visual snow diagnosis.
  • Furthermore, investigations to find out what causes VSS can be done by activating the ocular motor network using key tasks.

Key Definitions & Terms

1. Visual processing – Acquiring and transmitting visual information from the eyes, integrating and interpreting this information into a meaningful image to move the eyes or head.
2. Ocular motor network – The system responsible for moving the eyes and maintaining a stable visual image.
3. Stimulus – A visual event that brings about or increases the likelihood of an eye movement.
4. Central cognitive executive control – Integration of visual sensory information with a person’s intentions (derived from memory, attention, and psycho-emotional processes), resulting in the perception of a unified visual image within the brain’s consciousness.
5. Saccade – Quick movement of the eyes from one location to another.

What DId The Researchers Do?

  •  A group of people (64) diagnosed with visual snow syndrome had their visual processing observed. 
  • Afterward, researchers compared them with a control group (23) by studying the ocular motor network.
  • Three validated and distinct ocular motor tasks (e.g. a prosaccade, an antisaccade and an interleaved antisaccade-prosaccade) were perfomed.
  • Each task placed different demands on the ocular motor network
  • Therefore, allowing us to illustrate the types of visual processing changes occurring in people with the condition.

What Did The Researchers Find?

  • Fundamental execution of an eye movement towards a suddenly appearing stimulus in the visual field occurred faster in people with VSS than in the control group.
  • When people with visual snow syndrome performed the opposite action, i.e., prevent an eye movement towards a suddenly appearing stimulus, they were likelier to move their eyes towards the stimulus erroneously.
  • However, when a task’s difficulty level increased (i.e., requiring increased demands on central-cognitive executive visual processing), neither the faster eye movement response nor the proportion of erroneous eye movements changed.
  • Indicating that these visual processing changes are not a consequence of a disruption to the decision-making centers of the brain.
  • Instead, people with VSS appear to be processing visual stimuli more quickly than healthy people, leading to hyper-accelerated eye movements to visual stimuli.

What Does This Mean For Visual Snow Diagnosis

  • This research indicates a possible first-ever science-based visual snow diagnosis as revealed by, objectively using simple ocular motor tasks.
  • Changes seen in people with VSS indicate that their attention when filtering visual information may be affected and may be a contributing factor.

Written by Dr. Meaghan Clough, Post-doctoral fellow, Ocular Motor Research Group, Department of Neuroscience, Central Clinical School, Monash University. Here is the research summary: Fielding/White group


White OB, Clough M, McKendrick AM, Fielding J. Visual Snow. Journal of neuro-ophthalmology. 2018

Emma J Solly, Meaghan Clough, Allison M McKendrick, Paige Foletta, Owen B White, Joanne Fielding. Ocular motor measures of visual processing changes in visual snow syndrome. Neurology. First published July 16, 2020,

Contact Us

Associate Professor Joanne Fielding
Head of Ocular Motor Laboratory
Dept of Neuroscience, CCS
E: [email protected]

View PDF: VSI Monash_Visual Snow Syndrome Breakthroughs

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