The Damaging Effects of UV Light on the Human Eye

As Canadians, we know a thing or two about eye protection. If we are not dealing with the bright, muggy Canadian summers, we are dealing with the snow-blindness inducing long winters. Heck, we even invented them! It was the Inuit who were living in what is now northern Canada, who invented the first sunglasses composed of two horizontal slits fashioned out of ivory or bone.

We hear a lot in the news about the damaging effects of sun-exposure to the skin, but rarely do we hear about the significant damage the sun can have on the eyes. A recent study conducted in the United States showed that 79 per cent of people believe that sun is harmful to the skin, but only six per cent of people believe it is damaging to the eyes.

The eye is an incredibly complex and sensitive structure composed of many vital and vulnerable tissues. UV radiation affects almost every one of these tissues, starting with the eyelids, as well as the cornea and lens. It even affects the deepest structures within the eye, including the retina.

UV is considered, by the International Agency for Research on Cancer—an offshoot of the World Health Organization—as a group 1 carcinogen, which is the highest designation for cancer causing entities, sharing the spotlight with the likes of tobacco, x-rays and asbestos. More than one-third of all new cancers are skin cancers and up to 90 per cent of skin cancers are caused by UV exposure. The eyelid is an incredibly sensitive structure composed of the thinnest skin on the human body, making it more susceptible to UV damage. This explains why 5-10 per cent of all skin cancers originate around the eyelids.

Sun exposure can also lead to changes of the cornea, the clear front tissue of the eye. It can lead to formation of a growth on the cornea called a pterygium. If left untreated, a pterygium will continue to grow, eventually affecting an individual’s central vision. Another type of sun-causing growth is called a pinguecula. These types of growths are yellowish in colour and, if they grow large enough, can start to cause unsightly irritation and redness.

UV light is also linked to cataract formation. Cataracts are caused by oxidization changes within the lens, a structure located deeper in the eye. Cataracts are the leading cause of blindness in the world. Each year 12-15 million people around the world become blind from cataracts, of which up to 20 per cent may be caused or aggravated by sun exposure. It can also penetrate the far recesses of the eye and can even affect the retina contributing to the development of macular degeneration—a potentially vision-threatening disorder.

With the ongoing depletion of the ozone layer over the last decade, more and more UV light is penetrating the atmosphere—meaning it has never been more important to protect the eyes from the damaging effects of the sun.