SHADES of SUMMER

Eyeglasses have had their share of uncoolness, and wearers have heard it all: Geek. Nerd. Dork. And, of course, the classic: Four Eyes.

But somehow sunglasses, in all their dark-glass glory, have always been sweet. Big-deal rock stars wear sunglasses. Hot-stuff actresses wear sunglasses. Corey Hart wears sunglasses — at night, no less.

Plus, whatever style you embrace — the Jackie O bug eyes, the Ray-Ban aviators (thank you, “Top Gun”), or God forbid, those neon plastic ’80s shades — you can wear ’em with pride. Sunglasses offer more than just facial awesomeness. Nearly all shades on the market block harmful ultraviolet light that can lead to cataracts and eye cancer.

A recent study also suggests there’s reason to slip on your shades sooner and wear them longer. Japanese researchers concluded that UV exposure in early morning and late afternoon is double that of midday, what were once considered the most dangerous hours of sun exposure.

With help from Dr. Richard Davidson, practice director of the Rocky Mountain Lions Eye Institute in Denver, here are some other things you ought to know about your eyes, the sun and sunglasses.

NOT ALL SUNGLASSES ARE CREATED EQUAL

Sunglasses that wrap around the corners of the eye are more beneficial than ones that sit flat in front of the eye, Davidson said.

Flat-front glasses allow the wearer to open the eyes comfortably, but also allow UV light to enter the sides of the glasses, potentially increasing harmful exposure. Wrap-around sunglasses — and no, we’re not talking those massive granny-style shades that could double as shop goggles — are the best choice.

LIGHT EYES

Blue eyes have less pigment to absorb UV light, and people with light irises are often more sensitive to bright light. No color eye, however, is protected from UV light: Everyone needs sunglasses.

CAN YOU GO BLIND?

Mom always said it: “Don’t stare at the sun, you’ll go blind.” But will you? Definitely possible.

Staring at the sun can burn a hole in your retina.

THE PROBLEM WITH UV LIGHT

There are two types of ultraviolet light that concern eye health: UVA and UVB. Scientifically, the difference is the length of the wave. Medically, UVA penetrates the skin and causes wrinkles and increases cancer-causing effects of UVB, which makes the skin burn.

When talking about sunglasses, “UV protection” covers both types of light. Nearly all sunglasses found on the market offer UV protection, including most cheap ones.

Some contacts offer UV protection, but sunglasses are still needed to protect eye tissue. UV light is known to cause cataracts and skin cancer on the eyelid and surface of the eye. It is also suspected to contribute to macular degeneration, a general deterioration of the retina that can lead to legal blindness, Davidson said.

BLAME THE ALTITUDE

“We get more UV exposure than other places in the country” because of the elevation, Davidson said.

Outdoor enthusiasts need to pack a pair of sunglasses when skiing or boating, because the reflective surfaces of snow and water increase the harsh light of the sun.

Skiers are at particular risk for snow blindness — in which the surface of the eye is burned and vision is temporarily distorted.

Polarized lenses can help cut the reflection, although polarization doesn’t offer any additional health benefit, Davidson said. Neither does the color of the lenses; it’s a matter of preference.

TIPS FOR TOTS

Parents should pay special attention to the shades they put on their children. Some of the flimsy kids glasses don’t offer any UV protection (ones that do will be marked), but because the tinted lenses dilate the eyes, more UV light can enter than if the child had gone without.