For decades, treatments for a visual disorder called amblyopia, commonly known as “lazy eye,” have followed a one-size-fits-all approach. New research from the Department of Psychological & Brain Sciences at U of T reveals that the pattern of vision loss in amblyopia isn’t the same for everyone, and the key to better treatment may lie in understanding how each brain sees the world.

When we think of visual disorders, we usually think of diseases that affect the eye. However, not all visual disorders deal with just the eye. In fact, some of them deal with the brain, and researchers at the University of Toronto, including Dr. Anna Kosovicheva, have been examining individual differences regarding how our brain handles visual information to improve treatments for visual disorders, one of which is amblyopia. “It is a condition that affects not just the eyes, but it actually affects the brain,” Dr. Kosovicheva explained, underscoring why amblyopia cannot be simply “fixed” with glasses or corrected through optical means alone. The brain must learn or be retrained to see differently.

Amblyopia develops when the brain begins to favour one eye so strongly that it doesn’t use signals or information from the other eye. This is related to the idea of eye dominance, where your brain places a higher priority on input from one eye over the other. In typical eyesight, the brain prefers input from one eye, but still can use input from the other eye. However, in amblyopia, over time, the visual pathways linked to the weaker eye fail to develop properly, often because of eye misalignment or a difference in focus between the two eyes. Therefore, rather than being an issue with the eyes, the brain is also heavily involved in vision, especially in cases of amblyopia. Understanding this internal tug-of-war is crucial for developing successful treatments.

“The whole idea of underlying amblyopia treatment is that we want to find ways to even out that balance,” Dr. Kosovicheva explained, and it is precisely that balance that led to a surprising discovery in the team’s recent study. The study focused on identifying specific visual deficits in the vision of individuals with visual disorders such as amblyopia. In the study, they measured the degree of balance between the two eyes, using pictures that were placed in either peripheral vision (away from where they were looking) or central vision (directly at their point of gaze). Surprisingly, among the participants with amblyopia, the degree of imbalance was weaker n in their peripheral vision as opposed to their central vision. In other words, they were more able to use information from their two eyes in peripheral vision. This was counterintuitive, since peripheral vision is typically associated with worse function, as any image outside of central focus would appear more blurry.

What would the implications of better eye balance in the periphery have in clinical settings based on this study’s results? The findings suggest a deeper reality, where the amblyopic brain may be more adaptable than once believed. Dr. Kosovicheva finds these results particularly advantageous, stating, “The fact that we have coarser resolution, or a coarser ability to see detail in peripheral vision, can actually work to your advantage”. Rather than failing uniformly, the visual system appears to retain some spared function in an area where the two eyes still cooperate effectively.

Spared peripheral vision may be especially advantageous because it provides the brain with a more balanced and reliable source of visual input when central vision is weakened for those with amblyopia. Even though peripheral vision is generally less detailed, this preserved balance in people with amblyopia means the two eyes may end up working together more effectively in the periphery than at the center. This could have the potential to compensate for central deficits.

Still, relying on peripheral vision alone is far from a complete solution. Instead, these results highlight the importance of identifying individual deficits to tailor treatments to an individual’s needs. It’s a shift from treating amblyopia as a uniform condition to understanding it as a spectrum where it is essential to assess and cater to individual differences in vision from person to person. Future therapies may be able to utilize the brain’s stronger peripheral integration to reinforce the eyes to work together by using the visual system’s existing strengths, and focus on retraining the weaker central visual pathways.

This direction stands in contrast to traditional methods, such as eye patching. Eye patching involves an individual placing an eye patch on their dominant eye to encourage the brain to use information from the weaker eye. Although widely used, “the success rates for those kinds of treatments are typically around 50-70%, so while they are effective, they are not perfect,” Dr. Kosovicheva noted.

While traditional treatments may be successful, they may not be right for everyone, further fueling the need for personalized treatments. As Dr. Kosovicheva emphasized, “If we can understand something about the nature of deficits in amblyopia, then that might potentially guide future treatments.” Moving forward, uncovering these individual patterns of visual strengths and weaknesses will be essential for developing therapies and treatments that truly match each patient’s needs.

Ultimately, this research reveals something hopeful: even when the balance between the two eyes in central vision is compromised, the brain retains some spared function. Tapping into the brain’s adaptability may be the key to developing tailored therapies that can move amblyopia treatment beyond a “one size fits all” lens. After all, when it comes to vision, one size never fits all–it’s time to see the difference with a customized approach.