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The sun is essential for your survival, but too much sun exposure can damage the eyes, result in the body overheating, and can lead to death.
Eye injuries
It is important to take good care of your eyes when you are out in the sun.
This is because the eyes, without proper protection, can be damaged by the sun’s rays. Reduced vision and various eye problems can result.
Ultraviolet (UV) A and B rays from the sun can wreak havoc on the eyes, just as they can on the skin.
Macular degeneration
Besides UV rays, research has shown that high-energy visible (HEV) light, or harmful blue light, has been linked to eye problems too. It can damage the inner nerve layer of the eye (retina) leading to macular degeneration. The macula is the centre of the retina.
Retinal burn
Never look at the sun directly, said Dr Leonard Ang, the medical director of The Eye & Cornea Transplant Centre and The Premium Lasik Surgery Clinic.
The eye is extremely sensitive and can be burned by the sun’s UV rays, he said. After just one direct viewing of the sun, retinal burn can occur creating a blind spot that may be temporary or permanent. This is called solar retinopathy.
Even if the burn is temporary, such an injury to the retina, combined with sun exposure over a lifetime, will contribute to accelerated deterioration of vision or macular degeneration, said Dr Ang.
Cornea sunburn
Staring directly at the sun can also cause sunburn of the cornea. This is known as photokeratitis, a painful inflammation of the cornea.
The cornea is the transparent, dome-shaped surface of the eye that accounts for a large part of its focusing power.
Typically, the lens of the adult human eye will absorb some UV rays to protect the eye, said Dr Ang.
However, long hours in the sun or exposure to severe sun glare overwhelms these natural defences, causing sunburned eyes that result in photokeratitis. This condition usually heals on its own in about a week, he said.
Other eye problems
In the long run, overexposure to the sun, without adequate protection, is associated with eye conditions like cataracts, macular degeneration, pterygium and pinguecula.
Cataracts are clouding of the natural clear crystalline lens ofthe eye. This eventually leads to blindness for many, said Dr Ang.
Macular degeneration is a condition where the macula of the retina is progressively damaged by the formation of abnormal new vessels. (See macular degeneration above)
Pterygium is a triangular fleshy growth across the surface of the cornea. This may cause corneal problems as well as distorted vision if it is allowed to grow too large, said Dr Ang.
Pinguecula usually appears as a small yellowish lump which may occur near the cornea, he said.
The risk of all these conditions increases with extended exposure to the sun. This is because UV rays damage the cells and affect their healing mechanism, resulting in damage, degeneration or premature ageing of the eye tissue, said Dr Ang.
 Sunglasses
To protect the eyes from the sun's harmful UV and HEV rays, always wear good quality sunglasses.
Look for sunglasses that block 100 per cent of UV rays. They should also absorb most HEV rays, said Dr Ang.
The amount of UV protection sunglasses provide is unrelated to the colour and how dark the lenses are, he added.
A light amber-coloured lens can provide the same UV protection as a dark grey lens. An optician can help to verify if a particular type of lens provides 100 per cent UV protection, he said.
Choose frames with a close-fitting wraparound style because they limit how much stray sunlight can reach the eyes from above and beyond the sides of the lenses.
Remember to wear sunglasses in shady places too. Although UV and HEV exposure is reduced somewhat, the eyes will still be exposed to UV rays reflected from buildings, roadways and other surfaces, he said.
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