Think of sunglasses as an indulgence that’s actually good for you.

A pair of shades can hide tired eyes.

They can convey an air of celebrity.

They can conceal expressions of disgust, or say, boredom from partners in conversation.

All this, and more, comes while protecting eyes from the sun’s damaging ultraviolet rays.

“Sunglasses make men look macho and women look beautiful. People want to wear sunglasses not only to reduce glare and all that but because they just look better,” said Dr. Donald Borsand, president of Henry Ford OptimEyes, a chain of 32 optical stores in Michigan.

The pursuit of style has launched sunglasses into the realm of fashion accessory and helped drive the nonprescription sunglass market to $2.1 billion in sales in 2002, according to the Sunglass Association of America.

But fashion is only one component to consider when purchasing sunglasses.

The most important components are cost, quality, eye protection and deciding if the shades are mostly for show or for specialized pursuits such as volleyball, motorcycle riding or sailing.

Take a look at what the experts say about purchasing and wearing sunglasses.

RADIATION CAN HARM EYES

Squinting is not the first sign that it’s time to bring out the sunglasses.

Under bright or overcast skies, the sun’s ultraviolet rays, invisible light that can damage vision, can reach the eyes.

Most people grab shades only when they notice the light is irritating.

“You really should wear them anytime you’re outdoors or driving,” said Harry Lane of the Sunglass Association of America. “You’re getting ultraviolet radiation year-round.”

While UV protection shields the eye, it does not fend off glare or light that bounces off surfaces such as snow, sand or light-colored pavement.

Only polarized lenses or antiglare coatings can alleviate those discomforts.

Still, UV protection is the most important consideration when purchasing sunglasses.

There are three subranges in ultraviolet light, but only two, UVA and UVB, are of concern because they travel the farthest distance from sun to Earth.

Protective coatings on lenses can absorb ultraviolet light “and can help head off cataracts,” said Donald Borsand, president of Henry Ford OptimEyes, a 32-store chain of optical centers in Michigan.

Animal lovers even strap shades on their pooches.

But labeling and standards can be confusing.

The American National Standards Institute divides requirements for UV protection into three categories:

Cosmetic: Must block at least 70 percent of UVB and up to 60 percent UVA.

General purpose: Must block at least 95 percent of UVB and a minimum of 60 percent UVA.

Special purpose: Must block at least 99 percent of UVB and 60 percent UVA.

Keep in mind the standards aren’t mandatory, but many manufacturers exceed them.

For the best protection, choose sunglasses that block UVA and UVB rays between 290 and 400 nanometers.

Some labels express UV protection in percentages. Anything above 95 percent is good.

Some higher-priced products with polycarbonate glass or certain kinds of plastic lenses can claim to block 100 percent of UV rays.

For more information go to www.allaboutvision.com.