TOKYO—An international team of researchers has taken an important step toward understanding a powerful potential treatment for myopia, which is fast becoming a public health crisis in Asia. Previous work found that violet light can stop the progression of myopia, an elongation of the eye between the cornea and the retina that results in nearsightedness where far-away objects appear blurry. Now researchers at Keio University in Japan, Cincinnati Children’s Hospital Medical Center, the Georgia Institute of Technology, and Emory University have discovered that the protective effects of violet light depend on a newly discovered photoreceptor protein in the eye called OPN5, or neuropsin which was known to be sensitive to violet light.

“Among all the light reaches our eyes, we have known for sure that violet light is special,” said Toshihide Kurihara, MD, PhD, assistant professor at Keio University, located here. “The human eye seems to use it as a clue to control its size, whereas we knew neither the mechanism nor the necessity behind this phenomenon. We believe to elucidate this mystery might be the key to stop myopia pandemic and we have worked on it for years.”

A few years ago, the Keio team reported that violet light could prevent myopia progression. Violet light is abundant in outdoor sunlight but largely absent indoors, where it’s not emitted by artificial lights and ultraviolet protective coatings on windows also filter out violet light wavelengths.

In a paper scheduled to be published in the Proceedings of the National Academy of Sciences, the research team explained the molecular mechanism behind this violet light effect on myopia progression and presented a new function of the OPN5 protein. OPN5 is part of a group of photoreceptor proteins called opsins found in the membranes of cells that are not involved in forming visual images but that play other important roles in the eye.
The researchers used an established mouse model of myopia to demonstrate that without OPN5, violet light did nothing to halt elongation of the eye. Mice without the OPN5 protein also saw continued thinning of the choroid, a vascular layer that decreases in thickness in myopic eyes.
Understanding how violet light protects against worsening myopia is key as the condition’s prevalence accelerates, the researchers said. Their work was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology; the Tsubota Laboratory, Inc.; the U.S. National Eye Institute; the U.S. Department of Veterans Affairs; and the Emma and Irving Goldman Scholar Endowed Chair at Cincinnati Children’s Hospital Medical Center.