25. Optometry, eye-brain connections and Lyme disease

Episode 25 with optometrist Dr. Cameron McCrodan.

In the words of Optometrist Dr. Cameron McCrodan, “you don’t see with your eyes, you see with your brain.” What is the relationship between the eyes, the brain and some symptoms of Lyme disease? Dr. McCrodan explains that our brains are not only tasked with receiving visual stimuli, they also influence how the information is interpreted and how our eyes function. Although these topics were touched upon during his optometry education, his engineering mindset drew him to further explore this relationship between the eyes and the brain. As his knowledge expanded, he found that some of the symptoms his own family members were experiencing could be explained in this way, and his own practice evolved to embrace what he was learning and seeing in his own practice.

Beyond 20/20 vision 

“We often just think of our eyes as cameras that sort of take in the world, and we often overlook the fact that our brain is really what’s responsible for not only deciphering what comes in, and putting it together, but also for controlling what our eyes do, so it’s sort of a dual system.”

Dr. Cameron McCrodan

Dr. McCrodan describes neuro-visual performance as a more complex indicator of visual function than standard vision testing. He examines how the brain affects depth perception and how the brain controls whether the eyes work together. He is able to help athletes improve hand/eye coordination and help patients reduce symptoms such as sensitivities to busy visual environments like grocery stores. Dr. McCrodan mentions that because vision is neurologically controlled, diseases such as Lyme can have various effects on vision. He empathizes with Lyme patients who notice visual changes that may not be reflected in standard vision testing. These patients often require more in-depth testing to measure and determine whether the eyes and the brain are working together.   

The eye-brain connection and Lyme disease

Dr. McCrodan encourages optometrists to be aware of issues such as: light and screen sensitivity; headaches; trouble with focussing or reading; processing busy visual environments; issues with depth perception and spatial processing; and, dizziness and balance. He also points out that, because 70% of the information coming into our brains is visual, changes to our visual ability can also lead to brain fog. He stresses the importance of determining how well a patient’s eyes and brain are working together in order to determine what aspects of their vision may be treatable, and calls upon optometrists to consider Lyme disease in patients with these symptoms and to make appropriate referrals. Although optometrists cannot treat Lyme disease, they can support patients to improve their quality of life by treating the visual condition(s).

“Because vision is neurologically controlled, any kind of disease or process such as Lyme that can affect the neurological system, can also end up affecting how vision works…it can be incredibly frustrating for people with Lyme disease sometimes because they’ll often notice that their vision just doesn’t feel the same as it used to…and they’ll go for an eye exam or a test and be told that their eyes are physically healthy…but it’s actually a problem of how the eyes and the brain are working together.”

Dr. Cameron McCrodan

Many Lyme patients have challenges with equilibrium and balance, both of which are influenced by vision and depth perception. He notes that symptoms can range from balance problems, to dizziness to a milder “dis-equilibrium” that may be more difficult for patients to describe. Optometrists again play an important role in assessing for these symptoms. Dr. McCrodan touches on a couple of “self testing” modalities that may help determine whether symptoms can be attributed to the way our eyes and brains are functioning together. He describes the use and limitations of something called bi-nasal occlusion, which reduces the brain’s task of comparing visual fields of both eyes by blocking part of the visual field. He also refers listeners to a self test called “pattern glare” which assesses visual processing. Interestingly, he explains that researchers can use EEGs and actually see the difference when the brain is processing vision correctly or not. Contrast testing is another self test available on-line which is more directed at assessing the eye itself rather than brain involvement.

Improving quality of life by reducing symptoms

Did you know that glasses can sometimes lead to symptoms such as headaches? Dr. McCrodan describes a neuro-functional process for prescribing glasses that is aimed at improving vision clarity and reducing symptoms that are caused by the way our eyes and brains work together. Symptom reduction can also be achieved through vision therapy – therapies or exercises that help recalibrate the ways that the eyes and the brain work together. For example, for those who have issues with eye tracking while reading, there are exercises that train both eyes to work together. Dr. McCrodan elaborates on this, and other treatable visual symptoms in  his Tedx Talk from 2014.

“When a patient comes in who has Lyme disease…we want to separate kind of what’s visual, maybe related to the Lyme or not, from what is truly just the Lyme disease…a lot of the visual problems…may be a visual condition related to the Lyme disease, but the visual condition is treatable, and that’s where optometrists really need to look at a full work up of how the eyes and the brain actually work together.”

Dr. Cameron McCrodan

Dr. McCrodan highlights the role that optometrists can play in improving the quality of life for patients with Lyme disease, from a diagnostic perspective by knowing and recognizing symptoms, to therapies that may alleviate symptoms during both the early and later stages of Lyme disease. Sarah asks about the role of mold exposure and refers listeners to Dr. McCrodan’s book for a deeper dive into the relationship between our eyes and our brains. 

Thank you Dr. McCrodan for showing us that the interaction of our eyes and our brains are clear indicators of our health, our brain function, and of our well being! We look forward to hearing more about this exciting field of knowledge and the expanding role that optometrists have as new therapies are discovered.


“Our exposure, educationally to Lyme disease within Canada has been a trickier one…I know that a lot of my American colleagues…it’s been on the radar for a long time. Often up here it’s just said, ‘we don’t have it.’”

Dr. Cameron McCrodan

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