How Simple Eye Movements Could Spot Cognitive Changes

Sathishkumar S,  B.Optom

Research Fellow, Medical Research Foundation, Sankara Nethralaya, Chennai, India

Eye movements can reveal the first signs of cognitive decline before symptoms become noticeable. There are studies that have found that simple eye movements can provide crucial clues about our brain health, especially as we age. This blog explores how tracking those simple eye movements could be a key for early detection of cognitive changes. As we age cognitive changes are one of the serious issues, which might potentially affect our day-to-day activities. These all happen based on the changes in brain function. These changes are irreversible, so delay in diagnosis can become worse for our wellbeing. ⁽¹⁾ Our eyes don’t just help us see; they also reflect how well our brain is functioning. The areas of the brain that control eye movements are also involved in processes like attention, memory, and decision-making. When these cognitive functions start to decline, our eye movements change in noticeable ways. ⁽²⁾

Our quick eye movements are also known as Saccades are rapid movements that shift our gaze from one point to another. In healthy people, these movements are quick and accurate. But in those with cognitive impairments, saccades can become slower and less precise. ⁽³⁾ People with early Alzheimer’s often take longer to start saccades and their eye movements are less accurate. These changes can be detected through specific eye-tracking tests long before significant memory loss or other symptoms appear ^(4). Similarly, individuals with Parkinson’s may show slower and less accurate saccadic movements, reflecting impaired brain function. ⁽⁵⁾

On the other hand, smooth pursuit movements allow our eyes to follow moving objects smoothly. These movements are particularly sensitive to cognitive disruptions. People with ADHD often have trouble with smooth pursuits, showing frequent and inaccurate eye movements when tracking objects. This reflects underlying attention and processing issues. Also, patients with schizophrenia often show significant impairments in smooth pursuit eye movements, characterised by frequent interruptions. These changes can be early indicators of the disorder. ^(5,6)

But how to measure all these simple eye movements and use these as a specific indicator for the early detection or prediction of a particular condition. Modern eye-tracking devices use infrared cameras to capture eye movements with great precision. ⁽⁷⁾ This technology measures how long it takes to start a saccade, the accuracy of smooth pursuits, and how steady our gaze is. By analysing these factors, we can identify subtle changes that signal early cognitive decline.

In a recent study, they used eye-tracking technology to monitor saccadic movements in people at risk for Alzheimer’s. ⁽⁸⁾ Participants were asked to follow moving targets on a screen. Those who later developed Alzheimer’s had noticeable delays and inaccuracies in their eye movements compared to healthy individuals. This early detection method could lead to treatments that slow the disease’s progression.

This is the interesting future gap to assess the simple eye movements under an experimental setup with these different conditions could help spot individuals at risk early, which will allow timely management. Nowadays smartphones and computers come up with eye-tracking features, which can give their users continuous feedback on their cognitive health.

Using eye movements to detect early cognitive changes is a promising development in medical science. By focusing on specific, measurable aspects of eye movement, we could find powerful tools for early diagnosis. As this technology becomes more widespread, the simple act of moving our eyes could become a key to maintaining our cognitive health as we age.

References:

1. MacAskill, M. R., & Anderson, T. J. (2016). Eye movements in neurodegenerative diseases. Current opinion in neurology, 29(1), 61–68. https://doi.org/10.1097/WCO.0000000000000274
2. Anderson, T. J., & MacAskill, M. R. (2013). Eye movements in patients with neurodegenerative disorders. Nature reviews. Neurology, 9(2), 74–85. https://doi.org/10.1038/nrneurol.2012.273
3. Noiret, N., Vigneron, B., Diogo, M., Vandel, P., & Laurent, É. (2017). Saccadic eye movements: what do they tell us about aging cognition?. Neuropsychology, development, and cognition. Section B, Aging, neuropsychology and cognition, 24(5), 575–599. https://doi.org/10.1080/13825585.2016.1237613
4. Noiret, N., Carvalho, N., Laurent, É., Chopard, G., Binetruy, M., Nicolier, M., Monnin, J., Magnin, E., & Vandel, P. (2018). Saccadic Eye Movements and Attentional Control in Alzheimer’s Disease. Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 33(1), 1–13. https://doi.org/10.1093/arclin/acx044
5. Srivastava, A., Sharma, R., Sood, S. K., Shukla, G., Goyal, V., & Behari, M. (2014). Saccadic eye movements in Parkinson’s disease. Indian journal of ophthalmology, 62(5), 538–544. https://doi.org/10.4103/0301-4738.133482
6. Beltrán, J., García-Vázquez, M. S., Benois-Pineau, J., Gutierrez-Robledo, L. M., & Dartigues, J. F. (2018). Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer’s Disease: A Review. Computational and mathematical methods in medicine, 2018, 2676409. https://doi.org/10.1155/2018/2676409
7. Cognolato, M., Atzori, M., & Müller, H. (2018). Head-mounted eye gaze tracking devices: An overview of modern devices and recent advances. Journal of rehabilitation and assistive technologies engineering, 5, 2055668318773991.
8.  Molitor, R. J., Ko, P. C., & Ally, B. A. (2015). Eye movements in Alzheimer’s disease. Journal of Alzheimer’s disease, 44(1), 1-12.