Could being exposed to excess UV in the arctic lead to a human eye color change? If so, what is the mechanism?

Question

The CBS News article Expedition Antarctica: A father and son's journey to save the planet says (in part):

Thirty-two years ago, Robert Swan made history as the first person to walk to both poles. Even as a young man, these grueling expeditions took a harsh toll on his body. Passing directly beneath the hole in the ozone layer, Swan's face became badly burned and his eyes even changed color. But the Arctic explorer now says that all of that physical duress pales in comparison to the agony of watching his son go through the same experience 32 years later. (emphasis added)

Skin color change can happen after exposure to UV light. From Wikipedia:

Melanin is a natural pigment produced by cells called melanocytes in a process called melanogenesis.

Question: Can the human eye really change color due to excess UV light from the Sun, in this case through a polar "hole" in the ozone layer? If so, what is the mechanism?

above: "This winter, Barney and Robert Swan became the first explorers to ever trek to the South Pole surviving exclusively off of renewable energy." Robert (the elder) is on the right. From here. Credit: SHELL-Technical Partners

Answer 1

It's a four year old question and so far nothing definitive, but the September 30, 2022 BBC Future article How our eyes can change colour throughout our lives includes the following quotes from David Mackey, professor of ophthalmology in the Lions Eye Institute at the University of Western Australia.

Unfortunately there is no smoking gun here, yet.

Through apparently spontaneous change or through mishap or illness, our eyes can change colour in surprising ways.

But, surprisingly, our eye colour doesn't always remain constant throughout our lives – in fact, a wide range of external influences can change it, from injury to infection and sun damage. And sometimes the change appears to happen spontaneously.

It may be a similar story for eye colour, he suggests, with greater quantities of pigment building up in the months or years after birth. "The main pigment in the eyes is melanin and it's the way that melanin is distributed that gives you the different eye colours," he¹ says. "Simply classifying them: you've got blue eyes, some people also talk about grey but really it's a variant of the blue, then you've got the hazel and green combinations, and then you've got the brown, and that can be slightly brown or extremely brown. All of that's related to how much melanin is there."

Higher levels of melanin can have a beneficial function in intense sunlight – as in the skin, the pigment offers protection from sun damage.

In irises with little melanin, the blue colour comes from the way the fibres of collagen at the back of the iris scatter light, in the same way that the sky appears blue because of way light is scattered in the atmosphere.

As to why some children's eyes express more melanin over time, this remains mystery, says Mackey.

"We actually don't know what influences those colour changes," says Mackey, but there could well be an environmental factor at play. "You can almost say that for everything there's an interaction of genetics and environment, even for things we think of as totally genetic or as totally environmental," says Mackey. "But what environmental factors could influence it? We don't really have that data for the general population."

¹David Mackey, professor of ophthalmology in the Lions Eye Institute at the University of Western Australia.