SEEING THE SUNLIGHT: 3
Part 3 … and How UV Damages Your Eyes
BASIC STRUCTURES OF YOUR EYE
Your eyelid’s skin is exceedingly thin with contains numerous fragile components that can be injured by UV light. While your lens and the cornea work to filter UV rays, after many years of doing their job they can become damaged causing vision problems in later life.
Common eye disorders caused by UV radiation damage
PTERIGIUM (pronounced with a silent ‘P’)
Most authorities believe prolonged UV exposure causes this common cosmetic blemish where the conjunctiva (the thin, protective membrane covering the eye surface) grows onto the surface of the eye.
Sometimes the conjunctiva extends over the centre of the cornea, reducing vision and becoming inflamed. It can be removed by surgery, but often tends to recur.
A pinguecula (plural pingueculae) is very similar to a pterygium and often confused with it. However, it occurs only on the conjunctiva and doesn’t grow across the cornea.
Pingueculae are usually treated with eye drops. They may cause difficulties with wearing contact lenses, depending on the nodule’s location. In such cases (or if the pinguecula turns into a pterygium), surgery may be needed.
PHOTOKERATITIS and PHOTO-CONJUNCTIVITIS
Photokeratitis is an inflammatory reaction of the cornea (front layer of the eyeball), while photo-conjunctivitis is an inflammation of the conjunctiva.
Similar to sunburn, this very painful condition occurs when the very sensitive skin-like tissues of the eyeball and eyelids after a few hours of exposure to UV. Luckily, the damage is reversible and doesn’t generally result in any long-term damage to the eye or vision.
‘Snow blindness’ is an extreme form of photokeratitis sometimes experienced by skiers and climbers due to extreme UV exposure at high altitudes – fresh snow can reflect up to 80 percent of incidental UV radiation. Extreme UV levels kill the outer cells of the eyeball, creating vision loss.
Snow blindness is very painful while the body sheds the dead cells, but in the majority of cases new cells grow quickly and vision is restored within a few days. Very severe snow blindness may involve complications such as chronic irritations or tearing of the tissues.
AGE RELATED MACULAR DEGENERATION (AMD)
AMD usually affects people over 55 and is a leading cause of severe vision loss in the western world. It affects the macula – the tiny, central part of the retina at the back of your eye that’s responsible for your central, colour and detailed vision.
There are two types of AMD, which can affect one or both eyes. You may notice reading and close work becomes difficult. Blank areas or a grey/ black spot in the centre of your vision can develop, while your peripheral or ‘side’ vision usually remains intact.
Research suggests that AMD is the result of free radical damage, commonly caused by exposure to UV radiation (studies show many sufferers have a lifetime of greater UV exposure). Ageing, smoking, obesity and high blood pressure also appear to increase your risk of developing AMD.
Cataracts are the world’s leading cause of blindness. Every year some 16 million people in the world suffer from blindness due to a loss of lens transparency.
As proteins in the lens unravel, they tangle and accumulate pigments that cloud the lens with different degrees of severity. They can be surgically removed and an artificial lens or other means of optical correction can restore vision.
Cataracts appear to be enhanced by exposure to UVB. In fact, World Health Organisation estimates suggest up to 20% of cataracts may be caused by overexposure to UV radiation. This makes them avoidable through careful protection of the eye using sunglasses.
Current scientific evidence suggests different forms of eye cancer may be associated with lifelong exposure to the sun. Melanoma is the most frequent malignant cancer of the eyeball and sometimes requires surgical removal. The eyelids are also a common location for basal cell carcinoma (a more benign form of skin cancer).