According to almost any source about the light spectrum, visible light, the portion of the electromagnetic spectrum that is visible to the human eye, is the range of wavelengths between 400 to 700 nanometers.

Ultraviolet light (UV), which ranges from 10 to 400 nanometers, is not detectable to the human eye. Yet, new research from the University of Georgia found that people can see ultraviolet light, and the health implications may be significant.

In a study recently published in PLOS One, co-authors Billy R. Hammond and Lisa Renzi-Hammond show that 100 percent of the participants, all young adults, were able to detect an isolated UV peak at 315 nm.

“Every textbook that is written on vision, optometry, ophthalmology, introduction to psychology, sensation and perception all say the same thing, that humans cannot see ultraviolet light. We have now shown otherwise,” said Renzi-Hammond.

They also found that the ability to detect UV light dropped off dramatically among middle-aged participants, though it’s unclear why.

Renzi-Hammond, who studies the intersection of vision and health at UGA’s College of Public Health, says that the team didn’t set out to rewrite the rules on visible light. However, she continued, knowing that the eye can detect UV presents previously unknown consequences.

“From a health perspective, there’s a risk to the retina,” she said. “If you can see the light, it’s getting back to your retina, and in a way that could potentially be damaging.”

There may also be implications for therapies using UV light, including applications for skin conditions and mental health.

“Many of the tests proving out these treatments have been done in double-blinded studies. But what if the participants could see the light?”

These are among the many questions that need to be answer with future research across the field, says Renzi-Hammond. “Now that we know this fundamental fact about vision, there’s a lot more work to do to understand what this is contributing to us and what the potential harms are.”

The paper, “Individual variation in the transmission of UVB radiation in the young adult eye,” is available here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199940.

– Lauren Baggett

Additional coverage in the Aug. 24, 2018 issue of the ASPPH Friday Letter.

Posted on August 21, 2018.