What is ultraviolet radiation?
Ultraviolet (UV) radiation represents the sun’s invisible high-energy rays that lie just past the violet/blue end of the visible spectrum. UV radiation in sunlight mainly comprises of UV-A (315 to 400 nm) the long wavelength form of ultraviolet and the UV-B (280 to 315 nm) the short wavelength radiation. Little amounts of UV radiation are beneficial in the production of vitamin D in people. However, research has shown the UV-B to be more damaging.
Eyes and UV radiation
The eyes are recessed well within the head anatomically and shielded by the eyebrows and the eyelashes. Nonetheless, these adaptations are of limited use in protecting against UV rays under extreme conditions such as a strong ground reflection from snow, sand and water.
The closure of the eyelids, constriction of the pupil and the reflex of squinting helps in minimization of the penetration of the sunlight into the eye. The bright visible light triggers such mechanisms which are not seen with UV radiation. Hence, on a cloudy day, exposure to UV radiation can still be high. Consequently, the effectiveness of the eye’s natural defences in safeguarding against UV injury is limited.
Overexposure to UV radiation can lead to acute and chronic health effects on eye, skin and our immune system.
Eye diseases related to UV radiation
UV radiation plays a contributory role in the development of various eye disorders including:
- Cataracts: Worldwide, cataract is one of the leading causes of blindness and visual impairment. Cataracts refer to the cloudiness of the lens present in the eye, which develops gradually over a period (years). Cataracts have been linked with high UV-B exposure, as indicated by epidemiological studies. WHO estimations point to the fact that 20% of cataracts could be caused by UV overexposure and are hence avoidable.
- Pterygium: Prolonged UV exposure has been possibly linked with the unusual growth on the white of the eye. The pterygium can extend over the cornea and reduce vision. It can be treated by surgery, but the outgrowths tend to reoccur.
- Photokeratitis: It refers to the inflammation of the cornea. It is a painful condition arising out of excessive UV-B exposure of the cornea.
- Photoconjunctivitis: It is the inflammation of the membrane lining the eyelids, the eye socket and the conjunctiva. The sensitive cells of the membrane get damaged and cause pain upon overexposure to UV radiation.
- Cancer of the eye: Lifelong UV radiation exposure has been linked to various cancers of the eye. Cancer (melanoma) of the eyeball is usually reported that often requires surgical removal. The eyelids and facial cancer can arise by overexposure to UV radiation.
- Age-related macular degeneration: UV and intense violet/blue visible radiation exposure have been reported to damage the retinal tissues in the lab. Researchers have proposed that intense violet/blue light or chronic UV exposure can contribute to the ageing process in the retina.
Who are at risk?
All individuals, namely children, teens, adults and senior citizens are susceptible to the eye damage from UV radiation. Children typically spend more time outdoors that adults in the sunlight. The ultraviolet damage to the eyes can be cumulative in nature and can increase one’s risk of developing an eye disorder later in life.
Preventing UV radiation injuries of the eye
- Wear UV-blocking sunglasses and a wide-brimmed hat whenever you venture outdoors in the day. Even on cloudy days, the UV rays can pass the thin clouds and the haze.
- Never look at the sun directly including an eclipse. It can lead to damage to the retina and also cause solar retinopathy.
It is vital to safeguard our eyes from overexposure to UV radiation. The effects of ultraviolet are cumulative over the years and make young eyes more vulnerable. Prominence must be laid on starting eye protection from a young age.
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- What are the effects of UV on the eye? World Health Organization. http://www.who.int/uv/faq/uvhealtfac/en/index3.html. Accessed 10 Aug. 16.
- STATEMENT ON Ocular Ultraviolet Radiation Hazards In Sunlight. American Optometric Association. http://www.aoa.org/Documents/optometrists/ocular-ultraviolet.pdf. Accessed 10 Aug. 16.
- The Sun, UV Radiation and Your Eyes. American Academy of Ophthalmology. American Academy of Ophthalmology. http://www.aao.org/eye-health/tips-prevention/sun. Accessed 10 Aug. 16.
- Van Kuijk FJ. Effects of ultraviolet light on the eye: role of protective glasses. Environmental Health Perspectives. 1991;96:177-184.