Our Eyes and the Sun: Watch Out for Your Eyes

What are we exposed to?

To visible rays 

The radiation emitted by the sun travels through space and passes through the Earth's atmosphere before reaching us. It is partially absorbed by the various components of the atmosphere: ozone (whose protective layer blocks short-wavelength rays that would be lethal to living beings), the fine water vapor droplets that make up clouds, and the gaseous compounds in the air (oxygen, nitrogen, carbon dioxide...). The radiation that reaches us is therefore not the same as when it was emitted. It consists of 2 types of rays measured in nanometers (nm, 1 nanometer = 1 / 1,000,000th of a mm). 

To invisible rays

infrared rays, with a wavelength greater than 780 nm, which warm us, ultraviolet rays, between 280 and 315 nm (U.V.B.) and between 315 and 380 nm (U.V.A.). These are the most dangerous for the eyes. It is therefore essential to protect your eyes with sunglasses.

Radiation 

The "useful" radiation — that which warms and illuminates us — reaches us in three ways:

Directly

By diffusion through the atmosphere

After reflection off clouds, the ground, or a flat and light-colored surface — all the more so when the surface is light and reflective: sea, sand, lake, snow... — But also in everyday life: white walls, white paper, white tablecloths... This radiation is often overlooked, and therefore dangerous.

Ultraviolet rays are highly energetic, and their effects are all the greater the shorter their wavelength. All the tissues of the eye are affected by them.

But in an unequal manner:

The cornea absorbs up to 295 nm, thus all U.V.C. Rays (what remains of them after passing through the ozone layer), and a portion of U.V.B. Rays.

The crystalline lens absorbs virtually all U.V.B. Rays, and U.V.A. Rays to a large extent, and therefore suffers greatly.

The retina bears a heavy toll, all the more quickly and severely when the aggressions are repeated and/or intense. Certainly, the permanent biological renewal of cells constitutes the response to these aggressions, but if, from the earliest age, the eyes are not properly protected, all tissues are damaged.