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Concussion and Vision:
Understanding the Connection

A concussion is a traumatic brain injury caused by a blow or jolt to the head or body. While most people understand a concussion's immediate cognitive and physical symptoms, many are unaware of its profound impact on vision.

A concussion is a mild traumatic brain injury. Though often termed "mild," the effects can be severe and long-lasting. A concussion is a type of mild traumatic brain injury that occurs due to biomechanical forces acting on the brain. Understanding the mechanism of injury provides insight into the myriad of symptoms that can arise following a concussion and helps guide appropriate medical intervention.


Common causes include: Falls, sports injuries, car accidents, and physical confrontations.

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Basic Mechincanisms of a Concussion: 

Stage 1: Physical Mechanism: This can be due to both direct and rotational Forces

  1. Direct Impact: A blow to the head, such as from a fall or a collision, can cause the brain to collide with the inside of the skull. This direct force can injure the area of the brain near the point of impact.

  2. Rotational Forces: Even if there isn't a direct impact, sudden movements can cause the brain to twist or rotate within the skull. These rotational forces can be particularly harmful, leading to the shearing of nerve fibres (axons) throughout the brain. This diffuse axonal injury is often responsible for the widespread cognitive and functional disturbances in concussions.

Stage 2: Biochemical Cascade: The Neuronal Response

Following the initial physical insult:

  1. Ionic Flux: The traumatic forces disrupt the normal balance of ions (like potassium and calcium) inside and outside of neurons. This leads to a depolarization event, causing neurons to fire uncontrollably.

  2. Glutamate Release: The brain's primary excitatory neurotransmitter, glutamate, is released excessively. This overexcitation can be toxic to cells.

  3. Energy Crisis: The ionic imbalance and excessive neuronal firing require significant energy to restore normalcy. This occurs at a time when blood flow (and thus oxygen delivery) might be compromised, leading to an "energy crisis" in the brain.

  4. Inflammation: In response to the injury, the brain's immune response is activated, leading to inflammation. While inflammation is a natural part of healing, prolonged or excessive inflammation can further damage brain tissues.

Long-Term Vulnerability:

Following a concussion, the brain enters a vulnerable state. It's more susceptible to further injury, and another trauma during this window can lead to magnified symptoms and prolonged recovery, a condition known as Second Impact Syndrome.

The mechanism of a concussion injury is multifaceted, involving both immediate physical forces and subsequent biochemical reactions. Recognizing the intricacies of this injury helps in appreciating the importance of prompt medical evaluation, intervention, and adequate recovery time.

 It's crucial to note that while we have a growing understanding of concussions, research is ongoing, and our understanding may evolve. 

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How Does a Concussion Affect Vision?

When the brain suffers trauma, the areas responsible for vision processing can be disrupted. The relationship between concussions and vision is intricate. While a concussion is a brain injury, its effects can reverberate through various body systems, with the visual system prominently involved. 


When the head is subjected to a forceful impact or sudden movement, the brain can move inside the skull and come into contact with the bony structures, leading to bruising or injury. This impact can particularly affect the areas of the brain responsible for vision and balance, including the occipital lobe (vision) and parts of the brainstem and cerebellum that are integral to the vestibular system (balance and spatial orientation). Understanding these effects is crucial in recognizing, diagnosing, and treating post-concussion visual disturbances. 

Visual Pathways and the Brain:

The visual system is not just confined to the eyes. Visual information is relayed from the eyes through various pathways in the brain, finally reaching the occipital lobe, where it's processed. A concussion can disrupt these pathways at multiple points, leading to various visual disturbances.

 This can lead to symptoms like:

  •  Blurry or Double Vision: Difficulty focusing or simultaneous perception of two images of a single object

  •  Photophobia (Light Sensitivity): Discomfort or pain in bright light.

  •  Difficulty Tracking Objects: Challenges in following moving objects smoothly with the eyes.

  • Visual Midline Shift Syndrome: The perception that the visual midline is shifted can affect posture and balance.

  • Post-Trauma Vision Syndrome: A collection of symptoms, including reading difficulties, headaches, and reduced attention or concentration

Specific Visual Effects of Concussion:

  1. Oculomotor Dysfunction:

    • This refers to problems with the muscles that move the eyes. A concussion can affect the coordination and control of these muscles.

    • Symptoms: Double vision, difficulty tracking moving objects, eye strain, and difficulty shifting gaze between objects at different distances.

  2. Accommodative Dysfunction:

    • This disrupts the eye's ability to change its focus from distant to near objects.

    • Symptoms: Blurred vision, headaches, difficulty reading, and eye fatigue, especially during close-up tasks.

  3. Convergence Insufficiency:

    • In this condition, the eyes struggle to work together when focusing on a near object, leading one eye to drift outward.

    • Symptoms: Double vision, headaches, and difficulty reading.

  4. Visual Field Loss:

    • A concussion can cause parts of the visual field to be lost, leading to blind spots.

    • Symptoms: Difficulty navigating, bumping into, or missing objects in particular areas of vision.

  5. Visual Motion Sensitivity:

    •  An increased sensitivity to motion in the environment.

    • Symptoms: Dizziness or nausea when there's a lot of movement around, such as in crowded areas.​

  6. Photophobia (Light Sensitivity):

    • Description: A heightened sensitivity to light.

    • Symptoms: Discomfort or pain in bright light, squinting, or the need to wear sunglasses even in moderate light.

  7. Post-Trauma Vision Syndrome (PTVS):

    •  A collection of symptoms that arise due to the disrupted integration of the visual system with other systems post-concussion.

    • Symptoms: Spatial disorientation, balance problems, difficulty with visual memory, and an altered sense of one's position in space.

The visual disturbances following a concussion underscore the importance of comprehensive post-injury care. Individuals experiencing any visual symptoms after a head injury should seek consultation with a neuro-optometrist. Recognizing and addressing these issues can significantly enhance recovery and quality of life post-injury.


If you or someone you know has suffered a concussion and is experiencing visual disturbances, seeing a neuro-optometrist is vital. We can provide a comprehensive assessment and tailor treatments to individual needs. The implications of a concussion extend beyond the initial event. Its profound effect on vision underscores the need for awareness and timely intervention. Individuals can seek appropriate care and enhance their recovery by understanding the connection between concussion and vision.


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