Of all the light energy from the sun which reaches Earth, less than 10 percent is constituted by Ultraviolet-A (UVA) and Ultraviolet-B (UVB) radiation. Of this, UVA is up to 90 percent.
Normally humans can maintain health under average light conditions but prolonged exposure to high doses of UV radiation can cause significant damage to skin and eyes. Up to 50 percent of Ultraviolet radiation is emitted between 11 am and 2 to 3 pm.
Snow reflects up to 80 percent of UV light and even sand can reflect up to 25 percent UV rays causing damage to our skin and eyes. Acute effect on the cornea of the eye because of intense UV light causing pain and reduced vision is known as ‘snow blindness’. A similar picture is found in cases caused by exposure to severe UV radiation from arc welding.
Our body has some protective molecules which protect us from harmful radiation while there are some molecules which metabolize the damaging products of Ultraviolet radiation. The concentration of such molecules decreases as we age. That is the reason why Age-related Macular Degeneration (AMD) and cataracts are more common in older age group. These conditions result from prolonged and cumulative effect of UV radiation.
Studies have also shown that those who have lighter pigmented or blue irises have more incidence of Age-related Macular Degeneration. Those with brown irises have significantly lower incidence of AMD. The pigment in the iris filters out most of the Ultraviolet radiation and protects our eyes from the damage.
Pterygium which is a vascular growth on the surface of the eye is also caused by prolonged exposure to UV radiation.
Malignant melanoma which is a common cancer of the eyeball and Basal cell carcinoma which is a cancer of the eyelids are also associated with lifelong exposure to the sun (UV rays).
How to Minimize Exposure to Ultraviolet Radiation
It has been observed that people who spend most of their time indoors receive only one-fifth to one-tenth of the Ultraviolet load than those who spend most of their time outdoors. This suggests that we should spend less time outdoors especially in the day time more specifically between 11 am and 3 pm.
Using an umbrella can reduce up to 50 percent of ambient UV radiation.
During the day time especially in the summers, try to wear clothes which cover most of your body and a hat to protect your face.
Eyes can be protected with sunglasses with Ultraviolet protection. Prefer the ones with side shields. Beware of fake UV protection glasses. To be sure, never buy an unknown brand which is not reliable.
Sunscreens should be applied to those parts of the body which are not covered by clothing. The layer of sunscreen should be thick enough to provide good protection from UV rays.
Since the harmful effects of Ultraviolet rays vary depending on where you are living, the weather, time of the day, how cloudy or sunny it is outside and your own color of the skin and the iris, consideration of all factors is important to decide how much protection you need to prevent the long term effects of Ultraviolet rays.