Sunglasses are protective eyewear that is widely used by most people to prevent strong light from entering the eyes. They can also be a form of visual aid which incorporates coloured or polarized lenses. Despite its protective function, sunglasses are known as a fashionable item and they do add a sense of style to the wearer.
In the daytime especially between late morning until late afternoon, the sunlight can be very bright and glaring and this causes discomfort to the eyes. During outdoors activities such as swimming, fishing or gardening, a person will receive more light than a person who is doing indoors activities. As a preventive measure against the harsh sunlight, usage of sunglasses is highly recommended to protect the eyes from ultraviolet radiation, from the sun’s rays, which in the long term can cause serious eye problems.
Besides ultraviolet radiation, the rays from the sun that are damaging include bright white (visible) light and the blue end of the rays.
How does sunlight damage the eye?
Blue light from the visible spectrum. The ultraviolet radiation can be divided into 3 categories which are UVA, UVB and UVC. Ultraviolet radiation carry more energy than the visible light rays, therefore the eye is at risk of serious damage due to the absorption of the UV rays compared to other lights. Most of the damage that is caused by prolonged exposure from UV radiation are irreversible and can severely damage the eye. Therefore it is important to protect our eyes from long term exposure to UV radiation. Apart from damaging the eye, UV rays can also cause damage to the skin and body.
UV radiation can be absorbed by the various structures of the eye. The outer layers of the eye which are the cornea and the conjunctiva can absorb UVB rays. The lens absorbs mainly UVA rays. The retina (the light-sensitive lining) absorbs visible light. The UVC rays are already absorbed by the ozone layer and do not reach the earth.
UV radiation is part of the natural radiation found in the invisible light spectrum. Beside the sun as a natural source, UV rays can come from a variety of artificial sources which include welding equipment, lasers, tanning equipment and certain lamps. The damage that occurs in the eyes from these rays are:
- Cataract (clouding of the natural lens of the eye)
- Age Related Macular Degeneration (degeneration of the sensitive part of retina)
- Pterygium (a superficial growth in the conjunctiva)
- Retinal damage upon directly looking at the sun
The damage that occur in the body are :
- Sunburn of the skin
- Premature skin aging
- Skin cancer
- Weakening of the immune system
Selection of Sunglasses
For eye protection, it is recommended to wear sunglasses that blocks almost 100 percent or 99 percent of UV light. Plastic and glass lenses both absorb some UV light and this can be improved with lens material that has been treated with specific chemicals during the manufacturing process or by applying special coatings to the lenses.
Some basic advice when choosing sunglasses.
- Choose sunglasses with dark lenses to keep the eyes comfortable. Avoid very dark lenses as this can reduce vision. If a person has to spend time in the sun especially at the sea or during winter when there is snow, it is advisable to use sunglasses that blocks blue light from the visible spectrum. Select medium to dark sunglasses with either a grey, brown and green tint.
- It is recommended to use plastic lenses with a scratch-resistant coating rather than glass lenses as these lenses are tougher and less likely to break.
- Another type is polarized sunglasses which contains polarized filters. These filters can reduce glare and can reflect off light from shiny surfaces such as water.
Type of sunglasses
- Normal plastics lenses that reduce brightness evenly
- Polarizing lenses to cut glare due to reflection
- Photochromic lenses that changes colour with the intensity of the light which become darker when outdoors and lighter when indoors.
- Flash or mirror lenses type that reflect all or partial light instead of absorbing light.
Colour of sunglasses
- Grey or a green-tinted lens is suitable for both basic and multipurpose usage.
- Amber or orange lens will give a brighter view in cloudy, hazy or foggy weather because it helps to block blue light.
- Gold and yellow lenses can add contrast.
- Brown is good for enhancing depth perception.
- Rose lenses give high contrast and good image resolution in low light.
UV Protection offered by sunglasses
BEWARE that UV protection of a pair of sunglasses will not be based on the price, colour of sunglasses or by the darkness of the lenses. It is advisable to search for a label that lists the type and amount of protection offered by the manufacturer.
In term of UV protection, sunglasses that can be divided into three categories
- Cosmetic sunglasses have lightly tinted lenses for use in low levels of sunlight. They can block up to 60 percent of visible light and UVA rays, and between 88 and 96 percent of UVB rays.
- Multipurpose sunglasses block from 60 to 93 percent of visible light and UVA rays, and between 94 to 99 percent of UVB rays. They are mainly used for driving, and highly recommended in bright sunlight.
- Special purpose sunglasses block up to 96.5 percent of visible light and up to 98 percent of UVA rays. They also block at least 99 percent of UVB rays, and are generally used for prolonged exposure in the sun.
Besides wearing sunglasses that are properly chosen which can enhance the effectiveness of protection against damage from UV rays, bright light and blue light, there are other options which can be considered.
- Wearing a wide brimmed hat when outdoors in bright sunlight as this helps to protect the eyes by reducing the amount of light coming to the eye.
- Avoiding exposure to bright light during day time mostly between 11 am in the morning until 4 pm in the afternoon. During this period, UV radiation is the strongest. This is advisable for people doing outdoor activities such as swimming as the sand and water at the seaside can reflect UV radiation. Arrange to do outdoor activities either before 11 am or after 4pm.
- When spending time in the sun, find a shady area or use an umbrella.
The sun can be both a friend and foe. Remember these:
- Avoid prolonged exposure to direct strong sunlight.
- If you cannot avoid, use sunglasses with UV protection.
- When purchasing sunglasses, ask for and read the properties of the sunglasses, look for UV protection property.
Although sunlight is a source of energy that helps us in our daily activities, prolonged exposure in bright sunlight can cause damage to the eyes. Prevention is better than cure, so before you can see the effects and signs of damage to your eyes start applying the knowledge of the proper protection in the sun because it takes a short time before the sun can damage your eye permanently.
|Last Reviewed||:||23 August 2019|
|Writer||:||Lili Asma bt. Ismail|
|Accreditor||:||Profesor Dr. Azrin Esmady b. Ariffin|
|Reviewer||:||Dr. Rosniza bt. Ab. Razak|