If ever there were an ultimate testing ground for sunglasses, it’s Iraq, under the blazing sun and blowing sand, as sticky and scratchy as sugar.

So brutal are these conditions that some U.S. Marines in the past have brought in reinforcements of cardboard cutouts, affixed over sunglasses with slits to see through and to hold them in place, Maj. Riccoh Player said. Describing himself as a desk jockey this time around, Player saw such inventiveness in previous deployments, including Desert Storm.

“You’d rather have cardboard on your face than a scratched cornea,” Player said.

The civilian world hasn’t translated such extreme measures from war-zone desert to recreational beach. But manufacturers and athletes alike do take cues from these rigorous field tests for sunglasses that make function Job One.

“We began working with the military over 10 years ago,” said Colin Baden, president of Oakley Inc., a company best known for its eyewear, based in Foothill Ranch, Calif.

That unofficial alliance with Army and Navy special forces has influenced some of Oakley’s M Frame glasses. The wraparound style is designed to block the wind but not peripheral vision, without the distortion inherent in some wide-angle lenses. That appeals not only to soldiers but also athletes such as bicyclist Lance Armstrong and golfer David Duval.

Some Oakley innovations are available only to the military, for which it has a special sales force. That may explain why some soldiers are Oakley loyalists.

“Oakley and Ray-Ban are the two leaders, and Gargoyles – those are the top three,” Player said.

But mainly, troops look for no-questions-asked guarantees and lenses that are scratch-resistant and polarized, he said. Polarization reduces glare, which can be particularly blinding in sand and snow.

Tailoring choices to their needs, Laura Olinger, a spokeswoman for Bushnell, a company that owns several sunglass brands, arranged for donations to forces in and near Iraq.

Bolles, in the Coachwhip and Piraja styles, went to Marines. For Air Force special forces, she sent Serengeti Drivers glasses, which eliminate glare from the top without rendering planes’ instrument displays unreadable. That can be a problem with polarized lenses.

Whether civilians or soldiers, many underestimate ultraviolet radiation protection, said Dr. Lee Jampol, chairman of ophthalmology at Northwestern University Medical School. Cumulative exposure to UV rays can contribute to cataracts and macular degeneration, he said.

Dr. Donald G. Pitts, a former Air Force optometrist and spokesman for the American Optometric Association, has done extensive research on UV rays. He said it’s a myth that water is the riskiest reflective surface for UV. Water reflects 15 to 20 percent of those rays, snow up to 95 percent, and sand about 35 percent, he said.

Lying under an umbrella on a beach can backfire, literally. The cone shape collects the UV rays bouncing off the sand and directs them back in concentrated form, Pitts said. So no one should go without sunglasses even in shade. The bigger the lens, the better.

Tints are largely a matter of personal preference. But opticians and manufacturers say different tints tend to excel in different conditions.

Gray lenses are as all-purpose as tints come. Brown lenses suit golfers because they give sharper definition. Yellow increases contrast so is suited to dawn or dusk. Rose enhances depth perception in haze and helps the wearer see bumps on ski slopes, for example, Olinger said.

A red tint – trendy this year – “drives me crazy,” said optician Alissa Fields, who owns Eye Spy on Lincoln Avenue in Chicago. “It intensifies everything and brings out all the contrast. It’s hard to wear. It’s definitely more for fashion.”

For function with style, Fields said, her best-selling brands are Maui Jims and Persols.

Maui Jim, which boasts 100 percent protection from UV rays up to 400 nanometers, is prized primarily for its polarizing filters that block glare from above, below and behind the lens.

For that there’s a premium price: $249 is suggested retail for Titanium Sport pairs, the best-selling collection.

This month, Maui Jim debuts a stainless steel line, oriented to driving and casual wear, that is about $20 less than the titanium, oriented to recreation. Other lines in the brand start at $129.

No matter how how worthy the glasses, in some cases quantity is more crucial than quality.

For many Air Force pilots, classic Ray-Ban aviators retain dominance. But Air Force Tech Sgt. Karin Wickwire prefers no-name glasses.

“You lose the expensive ones but you hardly ever lose the $5 ones. And you don’t want to be out in this area without glasses,” said Wickwire, who has been south of Iraq for months.

“I came over with three pairs from the base exchange. And I still have all three. Not one of them cost me over $10.”

Spotlight-tested

Flashbulbs’ glare rivals that of sand for some celebrities, so no surprise that they wear them religiously, setting trends as they go.

What’s new this year?

• Oversized wraps or shields, with metal accents, a spinoff of the special-forces look that Madonna has been dabbling in. (The glasses she wore at a recent New York Tower Records appearance were the Yves Saint Laurent 2014S style, $200.)

• Red, or bordeaux, as in Salma Hayek’s Gucci 2499S frames, with burgundy gradient lenses, in the May issue of Harper’s Bazaar. (Price is $180.)

• Last year’s clear flash lenses, updated this year with light blue or brown hues. Reference: Brad Pitt’s light brown Dior Starlights, $250.

• Supersized rectangular and cat-eye shapes a la Jacqueline Onassis, but with new colors and lenses.

• Transparent frames, turning up in bordeaux, navy or gray. Robert Downey Jr.wears Gucci’s 2499S style, $180.

• Aviators, enlarged and reshaped from standard teardrop shape, maybe with one bridge instead of two.

• As for where fashion and function intersect, an example is Gucci 1712S sunglasses, with curved polarized lenses, worn by Adrien Brody at the Golden Globes. (Retail is $270.)

“I don’t think the military would be turning to Gucci for their sunglass needs,” Wexler acknowledged, “but if they were, these would be the perfect glasses. They keep the sun out as well as sand.

“Call it military chic.”

For starters, a store called Solstice is expanding from the East Coast and California, with the same sort of open-sell format, as opposed to locked cabinets, that cosmetics chain Sephora is thriving on.

Solstice focuses on fashion over function, said spokeswoman Eden Wexler.

It carries Oakley, Maui Jim and Ray-Ban, but its focus is more along the Christian Dior/Gucci/Yves Saint Laurent line, as seen in the following trends: