How does sunlight damage the eye?
The sun emits three types of rays: visible, infrared and ultraviolet (UV). The invisible UV light is the component of sunlight most responsible for eye damage. Excessive exposure to UV light from light reflected off sand, snow or pavement can produce a burn on the surface of the eye. Like a sunburn on the skin, eye surface burns are painful but usually temporary.
Eye damage from the sun can happen in one day or gradually over a lifetime. Repeated exposure to bright sunlight without adequate protection can damage the cornea (the outer transparent part of the eye that transmits light to the retina), the lens (the part of the eye responsible for focusing), and the retina (the innermost layer of the eye that transmits an image to the brain).
UV exposure is a risk factor for:
pterygium a fleshy growth that invades the corner of the eye
cataracts a clouding of the lens
macular degeneration a breakdown of the macula
Who is most at risk for eye damage by UV light?
People who spend considerable time in the sun or those who live at high elevation or near the equator;
Patients who have had cataract surgery;
Individuals who have retinal disorders;
People who are more sensitive to UV rays, including those taking certain medications, such as tetracycline, sulfa drugs, birth control pills, diuretics and tranquilizers.
How can you protect your eyes from UV damage?
You can greatly reduce your eyes exposure by wearing sunglasses and a wide-brimmed hat. The American Academy of Ophthalmology (AAO) recommends that sunglasses screen out 99 to 100 percent of UV light (both UV-A and UV-B).
What should you look for when purchasing sunglasses?
There are many different types of lenses and confusing claims made by the manufacturers. According to the AAO, here's what you should know about the following statements.
- Blocks 99% of ultraviolet rays - You should always buy sunglasses with this feature. Both plastic and glass lenses absorb some UV light, but UV absorption can be improved by adding chemicals to the lens material during manufacturing or by applying special lens coatings. Shop for sunglasses that block 99-100% of all UV light. Some manufacturers' labels say UV absorption up to 400nm. This is the same thing as 100% UV absorption.
- Blocks 90% of infrared rays Infrared wavelengths are invisible and produce heat. Sunlight has low levels of infrared rays. Some sunglasses manufacturers make health claims for their products based on infrared protection, but research hasn't shown a close connection between eye disease and infrared rays.
- Blue-blocking Whether blue light is harmful to the eye is still controversial. Lenses that block all blue light are usually amber and make your surroundings look yellow or orange. This tint supposedly makes distant objects appear more distinct, especially in snow or haze.
- Polarized Polarized lenses cut reflected glare sunlight that bounces off smooth surfaces like pavement or water. Polarization has nothing to do with UV light absorption, but many polarized lenses are now combined with a UV-blocking substance. Check the label to make sure the lenses provide maximum UV protection.
- Mirror-coated Mirror finishes are thin layers of various metallic coatings on an ordinary lens. Although they do reduce the amount of visible light entering your eyes, do not assume they will fully protect you against UV radiation.
- Wraparound glasses are shaped to keep the light from shining around the frames and into your eyes. Studies have shown that enough UV rays enter around ordinary eyeglass frames to reduce the benefits of protective lenses. Large-framed wraparound sunglasses can protect your eyes from all angles.
- Gradient lenses are permanently shaded from top to bottom or from top and bottom toward the middle. Single-gradient lenses (dark on top and lighter on the bottom) can cut glare from the sky but allow you to see clearly below. They are useful for driving because they don't dim your view of the dashboard, but they're not as good on snow or at the beach. Double-gradient lenses (dark on top and bottom and lighter in the middle) may be better for sports where light reflects up off the water or snow, such as sailing or skiing. Double-gradient lenses are not recommended for driving, because they make the dashboard appear dim.
- Photochromic - A photochromic glass lens automatically darkens in bright light and becomes lighter in low light. Most of the darkening takes place in about 30 seconds, while the lightening takes about five minutes. They come in a uniform or gradient tint.
- Ground and polished - Some non-prescription glasses are ground and polished when they are manufactured to improve the quality of the lenses. Non-prescription lenses that are not ground and polished will not hurt your eyes. You want to make sure that the lenses you buy are made properly. To judge the quality of non-prescription glasses, look at something with a rectangular pattern, such as floor tile. Hold the glasses at a comfortable distance and cover one eye. Move the glasses slowly from side to side, then up and down. If the lines stay straight, the lenses are fine. If the lines wiggle, especially in the center of the lens, try another pair.
- Impact resistant - All sunglasses must meet impact standards set by the Federal Food and Drug Administration. No lens is truly unbreakable, but plastic lenses are less likely than glass lenses to shatter when hit by a ball or stone. Most non-prescription sunglasses are plastic.
- Lens darkness - A medium lens is good for day-to-day wear, but if you use the glasses for very bright conditions, choose a darker lens. The color and the degree of darkness do not tell you anything about the lenses ability to block UV light.
How can you protect your child's eyes from the sun?
Because the lenses in their eyes are clearer, children's eyes are more susceptible to UV exposure. Here are some handy tips:
Keep children younger than six months out of direct sunlight.
Try to keep children out of the sun between 10 a.m. and 4 p.m., when the sun's rays are the strongest.
To help ensure your children wear their sunglasses, allow them to select a style they like. Many manufacturers make frames with cartoon characters or multi-colored frames.
Make sure your child wears a wide-brimmed hat or a baseball cap, which will provide some UV protection if he/she doesn't tolerate sunglasses.
Be sure to wear sunglasses or a hat outside yourself. Children often follow the example of their parents.
Remind children to wear their sunglasses or a hat even on cloudy days. Most of the sun's rays can come through the clouds on an overcast day.
Teach your children to never look directly at the sun.
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