As for the skin, the main danger to the eyes comes from the invisible components of the sun, including ultraviolet A and B (UVA and UVB). These rays, which concentrate a large amount of energy, strike the surface of the eye and are absorbed by all its tissues, where they commit sometimes irreversible damage.

It is therefore necessary to wear sunglasses on vacation, but also in town during the beautiful season because white stone facades or glass buildings reflect the rays.

The cornea, very exposed

Located on the surface of the eye, the cornea is on the front line. It takes one to two hours of brutal exposure to ignite and develop keratitis. It occurs six to twelve hours later as redness, tingling, tears, and visual disturbances.

"It is spectacular," says Dr. Marcel Ceddaha, ophthalmologist, but it usually heals in a few days. This superficial burn is dangerous only if it occurs repeatedly.

The lens, a fragile lens

The consequences of overexposure to the lens are more serious. This small transparent lens, placed behind the iris, has a solar capital that erodes over the years, like the skin. When it receives too much UV, it becomes opaque.

Result: a cataract settles prematurely. The vision begins to blur, "as if we were looking through a glass full of steam," says Dr. Marcel Ceddaha, Then it gradually decreases, until becoming inoperative.

The only solution to avoid blindness: to implant an artificial lens. According to WHO, 20% of cataracts are linked to excess sun.

The retina, little threatened

On the other hand, the rays do not alter the retina, which lines the back of the eye. Contrary to popular belief, UV does not accelerate the occurrence of age-related macular degeneration (AMD), which induces a permanent loss of central vision. "This hypothesis has been suggested several times, but no scientific study has proven the link between UV and AMD," says Professor Eric Souied, head of the ophthalmology department at the hospital in Créteil.

It could even be that the sun has a beneficial effect on the retina, because there is less case of AMD in countries with strong sunlight.

Which sunglasses to choose?

Choose glasses that have the CE logo and the frame is wrapped to avoid side radiation. Do not be fooled by the color of the glasses . We tend to think that the darker they are, the better the eyes are protected. But it's wrong: the color protects from glare, not UV. It is even the opposite: a dark glass devoid of UV filter causes a dilation of the pupils, thus a more massive entry of the rays inside the eyes. The UV protection is ensured by the material of the glass or by the treatment it has undergone .

In town, glasses of category 2 or 3 are enough. But by the sea, category 3 becomes essential because water and sand reflect up to 30% of the rays.

On the other hand, if you practice a water sport or hiking in the mountains, better category 4 glasses, even if the sky is veiled.