• 15 Jul, 2025
• Dr. David Schwirtz

Seeing Clearly, Thinking Sharply: The Overlooked Link Between Vision and Cognitive Health

Vision and Cognition: An Emerging Connection

The Brain’s Window: Why Vision Matters

The association between the eye and the brain is well documented. In fact, the light-sensitive part of the eye, called the retina, is an extension of and is directly connected to the brain. With this kind of connection, it’s no surprise that up to 80% of our experience of the world is visual. Vision is critically important for engaging with our environment. When a patient gets a new prescription for glasses, it’s not uncommon for them to feel a bit off balance as they adapt to clearer vision, and they need to use caution as they move around their world.

Cataracts and Cognitive Decline: A Preventable Threat

One example of a vision impairment that may be linked to an increased risk of dementia is cataract. Cataract is a condition where the clear lens on the inside of your eye becomes discoloured and foggy. The onset of cataract varies between individuals, but patients tend to notice symptoms in their 60s. These symptoms start out mild and can include changes in glasses prescription. As the condition progresses, vision will decrease and visual distortions, such as glare and halo, will start to occur, especially at night. What is particularly important is that cataract is quite common, and the prevalence increases with age. It’s estimated that more than 50% of individuals over the age of 80 have this condition or have already been treated for this condition.

Research shows that leaving a visually significant cataract untreated can cause areas of the brain to shrink. This means that proper care including diagnosis, monitoring and treatment of cataract is a promising modifiable risk factor for dementia.

The treatment for visually significant cataract is a surgery. During cataract surgery, the foggy and discoloured lens is removed through an incision that is millimetres in size and replaced with a man-made lens. Modern cataract surgery is a marvel; it uses technologically advanced equipment and the skills of talented eye surgeons. For a patient, this translates to a procedure that often takes 10-30 minutes to complete. Once complete, the recovery time is 3-4 weeks. Patients can see throughout recovery; visual clarity improves and toward the end of the timeframe they can be assessed to determine if a new pair of glasses would further improve their vision. Even still, any surgical procedure will be accompanied by risk and so it’s important to make sure that any decision to proceed with this type of surgery is based on an informed discussion with an eye doctor or eye surgeon.

Beyond the Eyes: How Vision Loss Affects the Whole Person

Vision impairment affects far more than sight, it impacts how individuals engage with the world around them. There is growing recognition within the clinical and research communities that vision loss contributes to social isolation, depression, anxiety, and, ultimately, is associated with cognitive decline in older adults. The connection between eyesight and brain health is both biological and behavioural: when vision deteriorates, people often reduce physical activity, withdraw from social settings, and forgo cognitively stimulating tasks, factors that, together, accelerate cognitive decline. Research has shown that clarity of vision matters when it comes to cognitive health. In one study, the researchers demonstrated that worsening visual clarity is associated with greater declines in language and memory.

Oculomics and AI: The Future of Eye-Based Diagnostics

Technology may act as a powerful healthcare tool. More specifically, oculomics is a fascinating area of study that was formally introduced in 2020 and touches on the relation between eye health and brain health. This field involves biomarkers which are unique molecules or characteristics that can be measured and can predict or diagnose a condition. We are finding that the eye may be a unique source of biomarkers that can tell us about things like cognitive health. Additionally, this research also shows that the eye has a connection to not only the brain but to the vascular, immune and metabolic systems.

One example of technology as a healthcare tool involves artificial intelligence-enabled retinal imaging. IRIS the Visual Group has actively been involved in developing such a tool since 2021. A retinal image is a picture of the light sensitive part of the eye and this technology has been around for decades. Our recent work has focused on using artificial intelligence to analyze these pictures. In this context, artificial intelligence is a software that highlights areas of concern in the picture, and then uses a database to better categorize the concern and identify if it might impact visual health. This software then produces a report that can assist an eye doctor with diagnosing, monitoring and treating eye conditions. Furthermore, the analysis can be used to help patients understand what is going on with their eyes and engage them in their care. The technology is continuing to improve because eye doctors can provide feedback to the software. The software has the capability to learn and adjust its analysis based on this feedback. While the doctor always makes the final decisions, this is an example where technology and doctor experience work collaboratively to improve patient outcomes. While it’s still early days and these tools aren’t yet widely available, it’s easy to imagine a future where they could even predict the likelihood of developing a vision impairment.

Taking Action: Eye Exams as a Public Health Strategy

It is estimated that nearly 1 million people in Canada will be living with dementia by 2030 and that this number increases to 1.7 million by 2050. The personal and societal cost of this condition is staggering, and so it’s important to do everything that we can to proactively address mitigatable risk factors. Vision is one of these factors and the Canadian Association of Optometrists provides guidelines on how frequently an individual at low risk should have an eye exam. For school age children aged 6-19 years old, you should have an eye exam annually. For adults aged 20-64, you should have an eye exam approximately every two years. For adults aged 65 or older, you should have an eye exam every year.

The topic of dementia is often accompanied by feelings of worry, anxiety and concern. Fortunately, vision health is a modifiable risk factor. With regular eye exams, earlier detection, and the integration of tools such as AI-enabled retinal imaging, there is a real opportunity to support cognitive health through better eye care. The growing field of oculomics, where the eye serves as a window into the brain, represents a powerful shift in how we approach both vision and neurological health.