What you should know about: Concussion and vision

Friday, March 8, 2024

Dr. Kristine Dalton on concussion and vision

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What is concussion?

Concussion is a type of mild traumatic brain injury where the brain is shaken inside the skull due to external forces such as a fall, blow to the head or whiplash. Concussions can cause several symptoms and signs even if standard diagnostic imaging such as a CT scan or MRI appears normal. A concussion can occur even if a person does not lose consciousness.

How can concussion affect vision?

An estimated 90 per cent of concussion patients experience some visual symptoms in the early days following a concussion. These symptoms may include headaches, dizziness, eye strain, visual fatigue, sensitivity to light, sensitivity to motion, blurry or double vision, and difficulty focusing or concentrating on what the eyes are focused on.

What are persisting concussion symptoms?

Most people with concussions recover fully in two to four weeks. In 15 to 30 per cent of patients, however, concussion symptoms take longer to resolve, sometimes lasting for months or years. These patients are said to have persisting concussion symptoms.

Some patients with persisting concussion symptoms may feel the symptoms they had in the early post-concussion days just don’t go away, while others experience a shift in symptoms or an easing of some but not others.

Some of the more common persisting vision symptoms include:

  • Difficulty focusing, especially changing focus from distance to near
  • Difficulty turning the eyes to maintain focus or track moving objects
  • “Tunnel vision” or being less aware of peripheral vision
  • Difficulty with visual concentration, including reading
  • Light and/or motion sensitivity
  • A feeling of overstimulation or symptoms flaring up in environments that are visually crowded, busy or bright, such as grocery stores
Injured soccer player

Causes of persisting concussion symptoms

Scientists don’t fully understand why some people’s concussion symptoms linger. However, one risk factor is having had previous concussions, especially multiple previous concussions.

Concussion disrupts the brain’s homeostasis, or state of balance, and can cause blood flow changes, axon (brain cell) injury, and inflammation that affects the brain. As a result, the brain may not work as well as it typically did while it is trying to heal and re-establish its normal balance.


A concussion is diagnosed by a medical doctor, who also makes initial treatment recommendations. 

However, if you are experiencing persisting concussion symptoms, assessment by a multidisciplinary team of healthcare providers is often needed. This team can include a combination of physicians, physiotherapists, vestibular therapists, optometrists, psychologists, occupational therapists, massage therapists, chiropractors, audiologists and dentists.

As assessment by an optometrist, particularly one with an interest or training in concussion management, may be helpful for lingering visual symptoms or vision issues. The objective of the optometrist’s assessment will be to determine if problems in the visual system are contributing to the persistence of concussion symptoms.

A full eye exam is an important part of the assessment. The optometrist will investigate whether trauma to the eye or eye disease may be contributing to symptoms. They will also determine whether the patient needs a new or different prescription for glasses or contact lenses.

If there is no damage to the structure of the eye and no need for a change in glasses or contact lens prescriptions, then the next step is to assess how well the two eyes are working together and how efficiently the patient is using their vision to navigate the world around them.


Sometimes simply updating a patient’s glasses or contact lenses is helpful. Other patients benefit from tints or filters on their eyewear to reduce glare or minimize certain types of light.

If updating eyewear isn’t sufficient to resolve patients’ symptoms, and there are lingering deficits in visual system function, such as difficulty with focusing, tracking moving targets, or how efficiently the two eyes are working together, vision therapy can be helpful. 

Vision therapy is akin to a strength and conditioning program for the eyes. As such, it involves targeted exercises for the eyes and visual system. Vision therapy can help improve how the eyes do things such as change focus and work together. 

Vision therapy is individualized – patients work on their specific deficits starting from their current ability level. It can be done in person, with regular visits to a vision therapist, or primarily at home, with patients getting trained on exercises, then working on their own for some time before returning for follow-up.

Exercises may be as simple as bringing a card close to the eyes and moving it away to work on changing focus. Other exercises may focus on tracking a moving object, visually “jumping” between separated objects, or encouraging the brain to use input from both eyes instead of relying on just one. Lenses or prisms might also be used to create different points of focus or encourage the eye to turn. 

prism flipper

A flipper lens used in vision therapy to mimic changing focus from distance to near

Waterloo Eye Institute patients

If you’re experiencing persisting vision symptoms following concussion, the first step is to call the Waterloo Eye Institute’s Brain Injury Service at 519-888-4567 x32395. Patients can self-refer or be referred.

If you haven’t had a full eye exam since your concussion, or if it’s been years since your concussion and your last eye exam was more than one or two years ago, you will be asked to have one, either with your normal optometrist or at the Waterloo Eye Institute. If your eye exam is done by your regular optometrist, you will be asked to sign a consent form so the Brain Injury Service can get a copy of the results.

If you would like to have your full (primary) eye exam at the Waterloo Eye Institute, call 519-888-4062 or book your appointment online. Primary eye exam appointments are available at locations in Waterloo or Kitchener. However, appointments with the Brain Injury Service are only available at the Waterloo location and must be booked by phone.

Once you’ve had your full eye exam, you will be asked to fill out an intake package giving details of your injury, symptoms and medical team. You may later be asked additional questions about your history.

The initial appointment with the Brain Injury Service is an assessment of every visual system that could be impacted by a brain injury. The objective is to determine how well your eyes are working independently and together. This assessment typically takes 1.5 to two hours, though it can be broken into two or more appointments if necessary. 

The initial assessment is in-depth and may trigger symptoms and/or cause fatigue. Some patients find they are more tired or symptomatic for a day or two following the assessment. If possible, plan to get a ride home and have a low-key day following the assessment. You can also bring a support person with you. Remember, you are in control – if you need to take a break or stop, let the clinician know.

The brain injury assessment costs $240 – note that all fees listed here are as of March 2024 and are subject to change. Follow-ups are $100 a visit and may focus on new glasses/tints, vision therapy or assessing your visual function to determine the effectiveness of treatment.

Typically, in-person vision therapy sessions are every week or every other week, but this may vary according to your needs, as will the number of sessions necessary. You will likely be assigned exercises to do at home between sessions. Partial reassessments are done about once every five sessions.

For at-home vision therapy, the first session following the assessment will train you on the exercises you will do. You will then work on them at home, with follow-up in-person sessions every four to eight weeks.

Whether you’re doing in-office or at-home vision therapy, there may be some equipment costs, typically between $25 and $150, with the higher end for people doing at-home therapy. 

OHIP does not cover post-concussion care or vision therapy, though some private insurers do, at least in part. If you are financially challenged, speak to our staff – there may be options to reduce costs (i.e. by doing at-home vision therapy) or apply for support from our charitable care fund.


The University of Waterloo School of Optometry and Vision Science is ranked fifth worldwide in research output for schools of optometry. Our researchers are actively working on better understanding and treating persisting post-concussion visual symptoms.

Because optometric care and vision therapy for post-concussion patients is relatively new, one avenue of research has focused on understanding the current prescribing and assessment practices of Canadian optometrists seeing patients with persisting concussion-associated vision deficits

Our researchers are also involved in the multi-institutional Eye Problems in Concussed Children (EPICC) study. Waterloo is the only Canadian site for the study, which locally is being done in partnership with Dr. Laura Purcell, a pediatric sports medicine physician, and Grand River Sports Medicine Centre. Participants who have had a recent concussion are still being recruited – if you know a young person aged 12 to 17 who has suffered a concussion within the last two to three weeks and is interested in learning more about the study or participating, please contact Dr. Kristine Dalton

Another avenue of research is focused on better understanding the experience and impacts of concussion on para athletes, specifically athletes with vision impairment, because pre-existing impairments can change how athletes experience concussion compared to athletes without an impairment. Resources our researchers have contributed to are available on concussion in blind or visually impaired athletes and concussion in para sport. There is an infographic on the latter topic.

For a broad look at optometry post-concussion, including some of the latest research, check out Dr. Dalton’s webinar for the Canadian Concussion Centre.

Interested in participating in research more generally? Check out our current studies recruiting participants