Secrets of color vision could hold clues to treating nearsightedness

A curious secret of color vision revealed by scientists

By K. R. Callaway edited by Tanya Lewis

The eye functions like a biological camera, utilizing surrounding light to form vivid images that aid navigation as visual beings. Similar to advanced cameras, the eye automatically adjusts its focus, yet it can only concentrate on a single wavelength or color at any given moment.

While this focusing peculiarity has been recognized for some time, the mechanism by which the eye selects a color to focus on has been elusive. A newly published study in Science Advances sheds light on this process. It reveals that our eyes do not merely focus on the brightest wavelength or the median colors of the visual spectrum. Instead, the color we perceive most clearly is determined by its dominance in our environment.

This discovery could provide insights into understanding and potentially treating nearsightedness, according to the researchers.

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“This is a great example of an aspect of vision that’s very automatic,” says Benjamin Chin, lead author of the study and assistant professor of imaging science at the Rochester Institute of Technology. “We don’t think about it, but it’s actually really complicated.”

The research initially aimed to address nausea in virtual reality by examining how eyes focus on color. Typically, our eyes align with the direction they are physically oriented, but virtual reality headsets can disrupt this alignment, leading to discomfort. Understanding that eyes focus on one light wavelength at a time, scientists explored whether color could guide focus in virtual reality. As the research progressed, it became evident that uncovering how the eyes select colors for clarity could also explain changes in the eye linked to conditions like nearsightedness.

Traditionally, it was believed that eyes focus to create the sharpest and brightest images possible, usually favoring the color green, which falls in the middle of the visible spectrum and is the color to which our eyes are most sensitive. However, not all stimuli contain green. To delve deeper, researchers examined the eye’s mechanics using study participants.

They developed an apparatus displaying images composed of red, green, and blue pixels. While participants viewed these images, a wave-front sensor analyzed how their eyes’ lenses adjusted to change the focal point. Similar to the focus test for glasses wearers, this device employed a weak laser reflecting off the retina for precise measurements.

“The best part of this paper, in my mind, is the theoretical modeling,” notes Shrikant Bharadwaj, a vision scientist at L V Prasad Eye Institute in India. The models, based on participant data, explored how focusing on different colors might influence visual sharpness.

“We saw this very systematic relationship,” Chin explains. “As one might expect, if the stimulus has a larger ratio of short wavelengths—blue—the focus will tend to be more on blue,” and the same is true of other wavelengths.

Nearsightedness, or myopia, occurs when the eyeball elongates, causing light to focus in front of the retina instead of directly on it. It generally develops in children and progresses into adulthood. Some studies suggest that close-up activities in low light, like reading or screen time, may contribute to this condition. However, the signals prompting eye elongation and whether certain colors induce enough strain for physical changes remain unclear.

Bharadwaj suggests that myopia may have various causes, with the chromatic signals discussed in the study being just one of many factors influencing eye growth.

Nevertheless, some labs are already experimenting with how exposure to or filtering specific light colors might affect myopia progression. Determining which colors the eye focuses on could help refine these efforts, aiding scientists in understanding the role of color in this condition.

“If you want to understand the long-term changes causing myopia, you also need to understand the short-term changes,” Chin says. “The real-time adjustment of the lens in the eye happens on a very fast timescale. We can accommodate in less than a second.”

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