There are 3 forms of ultraviolet (UV) radiation – UVA, UVB and UVC. Each is identified by it’s wavelength. UVA penetrates deeply into the skin causing tanning and aging.
The UVB wavelength is a little shorter and doesn’t penetrate as deeply as UVA. UVB is more damaging though, resulting in sunburn, blisters and skin cancers.
UVC is the most harmful to the skin. It can result in skin cancer, but fortunately, is absorbed by the ozone and doesn’t reach the Earth’s surface.
How does UV affect the eyes?
One of the most common conditions I see due to UV radiation is pinguecula. This is a raised nodule that appears on the white of the eye. It can become inflamed, discolored, and dry with chronic sun exposure.
Pterygium is a similar condition to pinguecula, but is grows onto the cornea (the clear part of the eye). Pterygia can grow and affect the vision. Removal is possible, but there is a high recurrence rate.
Photokeratitis is like a sunburn on the cornea, also known as “snow blindness.” Photokeratitis is directly attributed to environmental UV radiation exposure and generally occurs 8 to 24 hours after being in the sun. It is more typical in individuals who have not used sunglasses or hats. The primary symptoms include photophobia (extreme sensitivity to light) and pain.
One of the causes of cataracts is UV exposure. The crystalline lens is made up of proteins. These proteins can be altered or denatured by exposure to UVB or UVC radiation.
Age Related Macular Degeneration (ARMD) is another eye condition associated with UV exposure. The worldwide prevalence rate of ARMD resulting in impairment and blindness is 8.7%, making it one of the most common causes of blindness in patients over age 60. Studies have shown that many individuals with macular degeneration have had greater UV exposure over their lifetime.
Skin Cancers can present on and around the eyelids. Removal and excision is complicated by the importance of proper blinking and eyelid closure. Malignant melanoma can appear in the choroid (under the retina), the iris (colored part) and the conjunctiva (white of the eye). These tumors can be very aggressive. In fact, malignant melanomas of the choroid are the most common intraocular malignancy.
UV Protection with Spectacle Lenses and Sunglasses
Photochromic lenses, polarized lenses, sunglasses and high index lenses block 100% ultraviolet A and B radiation. But they don’t account for exposure due to reflected light or the light that reflects off the back surface of a lens. When the sun is lower, exposure to UV light actually occurs when the light hits at an angle, thus reflecting off the back surface of the lens and entering into the eye. This is also the time of day when sunglasses are less likely to be worn.
Environmental factors can increase UV exposure to the eye. For example, snow reflectance transmits 94% of UVA light and 88% of UVB light.
New technologies can eliminate backside UV radiation reflection and particularly focus on the shorter wavelength light, UVA and UVB. These coatings reduce glare, and provide full-spectrum blocking technology on both the front and back surfaces.