UV Light and Your Eyes
What is UV light?
UV is the type of radiation from the sun that causes sunburn and damage to your unprotected eyes.
As well as emitting visible light, the sun also emits short-wavelength ultraviolet (UV) radiation. The ozone layer absorbs the shorter, more hazardous, UV wavelengths and hence prevents them from reaching the earth's surface. This short-wavelength UV radiation can affect human health by causing skin cancer and affecting the immune system. It also contributes to various types of damage to the eyes (eg photokeratitis or snow blindness, and various opacities on and within the eyes, including pingueculae, pterygia and cataract).
When do I need to protect my eyes against short-wavelength UV radiation from the sun?
Amounts of potentially damaging solar UV are greatest at around local noon in mid-summer. They increase as we move towards the equator or to higher altitudes. Sand and snow tend to reflect substantial amounts of UV and hence increase damage risks. Protection is certainly needed during skiing or other activities on snow at high altitudes (particularly during summer) or on beaches, especially when these are near the equator.
How can I protect my eyes?
Wearing a broad-brimmed hat considerably reduces the amount of light striking the eyes when walking or standing. Ordinary clear plastic or high-index glass lenses provide considerable protection against short-wavelength ultraviolet radiation. Good quality sunglasses provide still better protection, although it is important to check that these are made to meet the British Standard for sunglasses (BS EN 1836:2005): category 2 (20% transmittance) give good protection. Protection against ambient ultraviolet coming from the side or reflected from below is also desirable, and with some modern small sized frames, care must be taken to check that they also protect from above.
Do I still need protection when the sky is cloudy?
Many types of cloud have only a small effect on the amounts of ultraviolet reaching the ground. lt is, then, prudent to continue to protect the eyes from ambient ultraviolet in high-risk environments even when the sky is cloudy.
Do I need to wear sunglasses in Britain whenever it is sunny?
While under most circumstances this is not necessary from the point of view of eye health when only relatively brief periods of exposure are involved, those spending many hours outside, particularly in summer in highly reflecting environments such as white sand beaches, should certainly wear them. Sunglasses can improve eye comfort for everyone in bright sunny conditions.
Are the risks likely to get worse in the future?
Scientists hope that the signing of the Montreal Protocol will stop the decrease in the ozone layer and make sure that we remain reasonably protected against short-wavelength UV sunlight. However, it is very difficult to predict exactly what will happen and a very careful worldwide watch is being kept on levels of both ozone and UV so that any worsening of the problem can rapidly be identified.
If I have exposed my eyes to too much short wavelength UV radiation, how will I know?
A few hours after the exposure your eyes will redden and water. They may feel ‘gritty’ and you may be more comfortable in a darkened room. Fortunately, this photokeratitis will subside within one or two days. The possibility of long-term effects cannot be excluded, however, so that it is worthwhile protecting your eyes when at risk in the future.