Most people now understand the importance of wearing sunscreen to protect against potentially harmful ultraviolet (UV) rays. Experts say, though, that protecting the eyes is just as important.

Many people wear sunglasses to keep their eyes out of the harsh glare of sunlight, for comfort reasons. However, sunglasses can also help to shield the eyes from UV rays as well. Although eyes have natural protection against the sun — they are set further in the skull, and are shielded by eyebrows, eyelashes, and the eyelid — they still can experience the same issues skin can, especially in extreme conditions.

According to Raj Das-Bhaumik, who works as a consultant ophthalmic plastic surgeon at Moorlands Eye Hospital in London, UV light isn’t only a threat in the summer, saying that “Snow and water reflect light including UV so the exposure is greater.”

Although it would be unethical for researchers to conduct experiments on humans to test the impact UV damage can have on eyes, observation of common conditions can help them draw inferences. One condition is known as “surfer’s eye” because it is often associated with surfers and other individuals who spend large amounts of time in the sun and around UV-reflective water. “Surfer’s eye” is pterygium, a benign growth of tissue that starts to cover the eye, and obscure vision.

Ultraviolet radiation can also cause melanoma cancer to develop, as well as lead to decreased vision. According to the U.S. Vision Council, many Americans are unaware of what they risk when they don’t protect their eyes — 43% were unaware it could cause eye cancer, and 49% didn’t realize it increased the likelihood of cataract development.

Professor Lilaine Ventura, from the University of Sao Paulo, has created a machine that measures the effective UV protection of sunglasses. Acknowledging that most people won’t have access to such a machine, Ventura says that individuals should choose sunglasses appropriate for the occasion. Polarized lenses are recommended for sports activities and for individuals who will be out on water — they help to reduce glare, protect against UV, while still allowing clear vision.