Visual health The sun and the eye
The sun provides light. Light permits vision. However, too much sun entails health hazards for the eyelids, the cornea, the crystalline and the retina which we shall describe here in order to understand how to protect oneself – and more specifically the retina with protective lenses – against these hazards.
"What are the risks for the cornea when exposed to too much sun? How should they be treated?
The cornea absorbs UV-B rays which can cause cornea burns such as snow blindness.
Snow blindness is caused by the reflection of UV rays on snow, the sea and sand. It occurs if the eyes are not protected.
It appears approximately two to eight hours after the exposure. Symptoms are stinging eyes, pain and red eye, watery eyes and a high sensitivity to light, leading in some cases to difficulty in keeping the eyes open.
Treatment consists in covering the affected eye with a bandage and prescribed analgesic to reduce pain.
Full recovery usually takes less than 48 hours. There will be no remaining damage.
What are the risks for the conjunctiva when exposed to too much sun?
Vernal keratoconjunctivitis commonly affects boys before puberty and is mainly observed in Mediterranean regions with outbreaks in summer. It is a form of allergy triggered by a hypersensitivity to light. It is the result of a hypersensitivity of the conjunctiva to heat and light. People affected by this are highly photophobic and avoid light. It lasts approximately ten years and disappears spontaneously. Further effects can include poorer visual acuity.
What are the risks for the retina when exposed to too much sun?
An excess of light to the retina causes a potentially painful glare. A prolonged exposure to direct sunlight (when observing a solar eclipse for instance) can cause burns at the centre of the retina. This is called solar retinopathy.
Symptoms are a black dot at the centre of the field of vision, an altered perception of colour and a distortion of straight lines that appear curved. Eyesight recovers spontaneously within some time between a few days and a few months, with the help of a cortisone-based local treatment.
How to protect the eyes from the sun?
The retina can be protected from the negative effects of UV rays by:
the eyelids that absorb them,
the cornea that absorbs UV-B rays,
the crystalline that absorbs UV-A rays.
It is however necessary to complete this protection with artificial protections: protective lenses."