Author: Vanessa Mora 

Role: Director of Research at VSI

A large percentage of our brain is involved in the visual processing of images and information. Visual processing focuses on identifying visual stimuli and their localization in space (1). Meaning that when looking at an item, your brain is trying to analyze and comprehend two questions: “what” and “where” (18). The cerebral cortex contains the systems and structures responsible for most of our “brain-work” during visual information processing. The cerebral cortex is the outermost layer, covering and supporting other brain structures, making up approximately 80% of the brain’s total volume. Visual stimuli from our surroundings are processed by neurons that connect from the optic nerve in the eye to the visual processing area in the brain known as the visual cortex (1). The visual pathway begins in the retina, a structure of many layers in the eye that consists of light-sensitive detectors known as rods and cones. The cones function in daylight conditions and provide color vision, whereas the rods function at night or in low-light conditions (12). These photosensitive reactions in the eye generate nerve signals in the brain that are converted into valuable and organized messages, recognizable shapes, and meaningful scenery as they travel through our brain (7). 

Our clarity of the world also goes further than visual processing and is connected to other senses. We must be able to navigate, maintain balance and hear our surroundings to direct our attention towards objects or events of interest, so that they can be registered by our vision and obtain an enhanced physical world experience. The vestibular apparatus in the inner ear sends afferent nerve signals to the brain that are responsible for our sense of proprioception and equilibrium (3). Orientation and navigation are achieved with the help of these functions, which move our heads in a specific direction accompanied by eye movements and posture. The auditory system in the outer, middle, and inner ear communicates through sound waves that travel to the cochlea, where inner hair cells synapse with neurons, facilitating auditory recognition (14). Through our auditory system, which processes our hearing and understanding of sounds in our environment, we can localize the sound source by communicating with our vestibular proprioceptive and visual system (8). 

Our quality of life, such as how we perform daily activities and interact with our environment, may be compromised when our visual processing system is not functioning correctly, supplying inaccurate or insufficient information to the other systems. Considering 50% of our brains are involved in our visual processing system, ophthalmic abnormalities following brain injury can produce a variety of dysfunctions and symptoms, negatively impacting our interaction with the physical world (2).

A concussion is the most common type of traumatic brain injury (TBI). It is most usually caused by a direct and quick bump, blow, or shock to the head, but it can also be caused by a body impact that causes the brain to move rapidly back and forth. As a result of this sudden movement, the brain can bounce around, creating chemical changes and sometimes stretching and damaging neurons, resulting in neurological dysfunction (5). A concussion can occur in various settings, including at work, school, motor vehicle accidents, sports, recreational activities, being struck by an object, assault, and even a regular fall (17). Most patients who suffer from a concussion will recover quickly (two weeks) from their post-concussive symptoms, returning to their normal activities. However, others may experience symptoms that remain and interfere with their everyday functioning. When symptoms of postconcussion persist over three months, it is called persistent postconcussion syndrome (PPCS) (13).

It has been demonstrated that some patients who experienced a concussion also had a probable trigger for Visual Snow Syndrome (VSS) (16). VSS is a neurological condition, where the main symptom is the appearance of flashing dots or static, known as visual snow (VS) (9.) VS appears throughout the visual field and can be either chromatic (colored) or achromatic (not colored) (4). To be diagnosed with VSS, visual snow should persist for more than three months (19), similar to the diagnostic time frame given for PPCS. Alongside visual snow, at least two of the following symptoms are required for VSS diagnosis: blue field entoptic phenomenon, excessive floaters, nyctalopia, palinopsia, photopsia and photophobia. In fact, PPCS and VSS share similar symptoms, as shown in Table 1. As a concussion or other forms of brain injury causes direct or indirect damage to the brain and to the neuron’s integrity, it is proposed that such areas of the brain are responsible for visual processing, which contribute to the symptoms of a concussion, and in theory to VSS symptoms (11). A case study describes a 28-year-old female who sustained multiple concussions after three motor vehicle accidents over a decade. Before her concussions, she was asymptomatic; after the second concussion, she experienced VSS symptoms including VS, palinopsia, photophobia, and migraines. After the third concussion, her symptoms became more severe, including VS, blurry vision, diplopia, fatigue, concentration difficulty, floaters, photophobia, palinopsia, motion sensitivity, and dizziness. The Intuitive Colorimeter used the treatment of chromatic filtration to reduce the patient’s symptoms. The specifications she preferred were : hue = 150, saturation = 30, and overall transmittance = 39%. With the chromatic filter, her VSS symptoms reduced and improved her comfort. For using technology devices, the color modification was accommodated on her iPhone, which mimicked the effects of the Intuitive Colorimeter (10).

Overall, knowledge about VSS and its associated comorbidities to physicians, healthcare professionals, and the general public is essential for VSS diagnosis if experiencing the symptoms presented in the diagnostic criteria following a concussion or multiple concussions. It is also critical for others to know that while VSS is associated with post-concussion syndrome, people without a history of concussions can also develop VSS (15). Further research on the relationship between VSS and PPCS can be investigated to aim for a better understanding of the pathophysiology and treatment methods. 

Steps to set up chromatic filter on iPhone IOS 15.5:

Go to Settings 

→ Click on Accessibility 

→ Click on Display & Text Size 

→ Click and turn on Color Filters 

→ Find the hue and intensity that suits your symptoms best 

1.Ackerman,S.(1992). Major Structures and Functions of the Brain. National Academies Press (US). 

2.Alvarez, T. L., Kim, E. H., Vicci, V. R., Dhar, S. K., Biswal, B. B., & Barrett, A. M. (2012). Concurrent vision dysfunctions in convergence insufficiency with traumatic brain injury. Optometry and vision science : official publication of the American Academy of Optometry89(12), 1740–1751. https://doi.org/10.1097/OPX.0b013e3182772dce

3.Casale, J., Browne, T., Murray, I. (2022).Physiology, Vestibular System. StatPearls Publishing. 

4.Ciuffreda, K. J., Han, M. H. E., Tannen, B., & Rutner, D. (2021). Visual snow syndrome: Evolving neuro-optometric considerations in concussion/mild traumatic brain injury. Concussion6(2). https://doi.org/10.2217/cnc-2021-0003

5.Ferry, B., DeCastro, A. (2022). Concussion. StatPearls Publishing. 

6.Gunasekaran, P., Hodge, C., Rose, K., & Fraser, C. L. (2019). Persistent visual disturbances after concussion. Australian journal of general practice48(8), 531–536. https://doi.org/10.31128/AJGP-03-19-4876

7.Gupta, M., Ireland, A.C., Bordoni, B. (2021). Neuroanatomy, Visual Pathway. StatPearls Publishing

8.King A. J. (2009). Visual influences on auditory spatial learning. Philosophical transactions of the Royal Society of London. Series B, Biological sciences364(1515), 331–339. https://doi.org/10.1098/rstb.2008.0230

9.Klein, A., & Schankin, C. J. (2021). Visual Snow Syndrome as a network disorder: A systematic review. Frontiers in Neurology12https://doi.org/10.3389/fneur.2021.724072

10.Klein, A., & Schankin, C. J. (2021). Visual Snow Syndrome as a network disorder: A systematic review. Frontiers in Neurology12https://doi.org/10.3389/fneur.2021.724072

11.Mehta, D. G., Garza, I., & Robertson, C. E. (2021). Two hundred and forty-eight cases of visual snow: A review of potential inciting events and contributing comorbidities. Cephalalgia41(9), 1015–1026. https://doi.org/10.1177/0333102421996355 

12.Moschos M. M. (2014). Physiology and psychology of vision and its disorders: a review. Medical hypothesis, discovery & innovation ophthalmology journal3(3), 83–90.

13.Permenter, C. M., Fernández-de Thomas, R. J., & Sherman, A. L. (2022). Postconcussive Syndrome. StatPearls Publishing. 

14.Peterson, D. C., Reddy, V., & Hamel, R. N. (2022).Neuroanatomy, Auditory Pathway. StatPearls Publishing

15.Puledda, F., Schankin, C., Digre, K., & Goadsby, P. J. (2018). Visual snow syndrome: What we know so far. Current Opinion in Neurology31(1), 52–58. https://doi.org/10.1097/wco.0000000000000523 

16.Solly, E. J., Clough, M., Foletta, P., White, O. B., & Fielding, J. (2021). The psychiatric symptomology of visual snow syndrome. Frontiers in Neurology12https://doi.org/10.3389/fneur.2021.703006

17.Tator C. H. (2013). Concussions and their consequences: current diagnosis, management and prevention. CMAJ : Canadian Medical Association journal = journal de l’Association medicale canadienne185(11), 975–979. https://doi.org/10.1503/cmaj.120039

18.Terpening, Z., & Watson, J. D. G. (2007). Higher visuoperceptual disorders and disorders of spatial cognition. Neurology and Clinical Neuroscience, 59–71. https://doi.org/10.1016/b978-0-323-03354-1.50009-2 

19.Yildiz, F. G., Turkyilmaz, U., & Unal‐Cevik, I. (2019). The clinical characteristics and neurophysiological assessments of the occipital cortex in visual snow syndrome with or without migraine. Headache: The Journal of Head and Face Pain, 59(4), 484–494. https://doi.org/10.1111/head.13494

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