SOME PEOPLE ARE AT GREATER RISK FOR UV–RELATED EYE DAMAGE

Some studies show that people with certain eye diseases such as macular degeneration and retinal dystrophy may be at greater risk for UV-related sun damage. As a precaution, they should wear sunglasses whenever they go outside.

A number of scientific studies indicate that spending long hours in the sun without eye protection can damage your eyes by contributing to cataracts, macular degeneration, and growths on the eye, including cancer. Based on these studies, ophthalmologists recommend that you wear 99% and above UV-absorbent sunglasses and a brimmed hat whenever you’re in the sun for long periods of time.

WHEN TO WEAR SUNGLASSES

Sunglasses should be worn anytime you are outdoors, particularly under these circumstances:

• During the summer, when the level of   ultraviolet radiation

   (UVA and UVB) is at least three times higher than during the winter

• When at the beach or in the water

• When participating in winter sports, especially at high altitudes

WHAT TO LOOK FOR WHEN PURCHASING SUNGLASSES

Most sunglasses are designed to protect our eyes from the sun’s harmful effects. Often the labels on sunglasses promise protection from ultraviolet light and other kinds of natural radiation. It is important to know what kind of light you need to protect your eyes from and what type of light is not necessarily harmful.

Blocking  99% of ultraviolet rays

You should always buy sunglasses with this feature. Long-term exposure to ultraviolet (UV) radiation in sunlight is linked to eye disease. UVB radiation is considered more dangerous to the eyes and skin than UVA radiation. 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.

Look for sunglasses that block 99% or 100% of all UV light. Some manufacturers’ labels say “UV absorption up to 400nm.” This is the same thing as 100% UV absorption.

Blocking  99% of infared rays

Infrared wavelengths are invisible and produce heat. Sunlight has low levels of infrared rays, and the eye tolerates infrared well. Some sunglass manufacturers make health claims for their products based on infrared protection, but research has not shown a close connection between eye disease and infrared rays.

Determining 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.

IMPACT-RESISTANT

All sunglasses must meet impact standards set by the Federal Food and Drug Administration (FDA) for safety. No lens is truly unbreakable, but plastic lenses are less likely than glass lenses to shatter when hit by a ball or stone.

Most nonprescription sunglass lenses are plastic. Polycarbonate plastic, used in many sports sunglasses, is especially tough, but it scratches easily. If you buy polycarbonate lenses, look for ones with scratch-resistant coatings.

POLARIZED LENSES

Polarized lenses cut reflected glare—sunlight that bounces off smooth surfaces like pavement or water. They can be particularly useful for driving and fishing. 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.

PHOTOCHROMIC LENSES

A photochromic glass lens automatically darkens in bright light and becomes lighter in low light. Most of the darkening takes place in about half a minute, while the lightening takes about five minutes. Photochromic lenses come in a uniform or gradient tint. Although photochromic lenses may be good UV-absorbent sunglasses (again, the label must state this benefit), it takes time for them to adjust to different light conditions.

WRAP-AROUND LENSES

Wrap-around glasses are shaped to keep 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

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. They’re not as good, however, at reducing glare in snowy surroundings 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.

MIRROR COATED LENSES

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.

BLUE-BLOCKING LENSES

Whether blue light is harmful to the eye is still controversial. Lenses that block all blue light are usually amber colored and make your surroundings look yellow or orange. The tint supposedly makes distant objects appear more distinct, especially in snow or haze. For this reason, amber sunglasses are popular among skiers, hunters, boaters, and pilots.