Both Jimmy and Rosalynn Carter wear them.

President Reagan wears them.

Some 14 million Americans, in fact, know what it's like to grope desperately in the grass, in the gutter, on the bathroom floor, blindly -- and that's no euphemism -- searching for that dropped contact lens. . . .

Cosmetically, of course, contact lenses are the perfect answer for people still worried about glasses dampening passes. (Although this doesn't seem to be a deciding factor for most Americans: About 40 percent of this country's vision-corrected use contact lenses as opposed to, for example, Australia's vain 70 percent.)

But contacts have other advantages, and they are getting better and better.

In fact, says optometrist Fred Elias Goldberg, former staff consultant to the American Optometric Association, there will be disposable versions one of these days. "You'll buy them like pantyhose," he predicts.

Also in the works: lenses made rather like those gloppy plastic toys -- with plastic material injected into molds to create lenses quickly and easily, while lowering the chance of error, along with cost.

Latest in the contact-lens inventory are extended-wear soft lenses, just approved by the FDA, which permit wearers to leave them in place for days, sometimes weeks at a time. And although it is not recommended, sometimes they can stay in for months.

They are, so far, available only for people whose vision problem stems from near-sightedness, and they are more expensive (about $350) than other types of lenses, in part because they require more skillful fitting and more intensive follow-up programs.

But they are singularly useful for certain patients, and in fact, have been available here for about two years for people recuperating from cataract operations.

The extended-wear lenses are mostly water so they permit a great deal of oxygen to permeate the surface of the eye. It is a lack of oxygen that causes most of the so-called "overwear syndrome" associated with overuse or misuse of other contacts, hard or soft.

Topping the list of advantages for the new lenses, of course, is convenience, a characteristic which can be overriding when dealing with children, Parkinson's victims, or victims of other diseases and disorders which affect coordination.

Goldberg also sees great advantages for emergency personnel such as fire fighters who may not be able to stop (for example) to take out and clean lenses -- or sportsmen, or anyone who travels a great deal. Also, says Goldberg, people who must -- like hospital interns -- catch sleep when they can.

But while fine for sunbathing and napping, the extended-wear softies are not, he notes, for swimming: They're held in the eye by the surface tension of water. If there's water on both sides, he says with some understatement, "there is the potential for the lens being washed out." (Care should be taken in bath and shower as well.)

Because they are handled less, there's less chance of loss, damage or contamination, despite their natural fragility.

And of course, says Goldberg, they have all the advantages contacts generally have over glasses. There is a greater field of vision; a greater mobility of vision so that as you turn the eye, you're always looking through the most optically clear portion of the lens. Also they don't fog up and they don't fall off your nose.

On the other hand, they may not be good for everyone. They do not correct for astigmatism, although there soon may be some which will.

Part of the added expense for extended-wear lenses comes from the need for maintaining a proper fit. Wearers must been seen regularly by the fitting doctor -- as often as six times a year after an initial six months of weekly visits -- which is essential says Goldberg, to the health of the eye.

Because they stay in so long, there will be an inevitable build-up of mucous which eventually will shorten the lens life.

Even if extended wear is not appropriate for an individual, there is such variety in contacts these days, says Goldberg, that many more glasses wearers could use them than now do.

For example, although bi-focal contact lenses are generally not satisfactory, a system known as "monovision" -- a distance lens is used on one eye and a reading lens on the other -- is proving successful in about 75 percent of those trying it.Goldberg estimates that monovision patients now account for about 20 percent of his practice. (Monovision is popular, apparently, in the White House. It was the contact-lens choice of the Carters, and the work in the eye-care community is that President Reagan also uses them.)

"People are just amazed," says Goldberg. "The biggest problem is to convince people that it doesn't change the normal functioning of the eye. Once the eyes learn how to see properly they never forget. Once they try, most are enthusiastic even if they're baffled as to how it works."

(You do need backup glasses for things like night driving where depth perception within 20 feet is crucial, he says, "but all contact wearers should have backup glasses, anyway." He recommends sunglasses in bright sunlight.)

Goldberg, who practices in McLean and Middleburg, is so enthusiastic about the proper use of contact lenses that he maintains a 24-hour consultation number for worried wearers -- whether or not they are his patients. He will answer any questions at any hour of the day or night, although he limits night calls (between midnight and 6 a.m.) to emergencies. There is no charge for his phone consultations. The number: (703) 827-0694. t

Goldberg agrees that consumers of "vision delivery" services, as the MD ophthalmologists call it, should investigate -- and interview -- those who sell and fit glasses and contact lenses. Check credentials and arrangements for follow-up examinations. Don't give in to the hard sell.

The American Optometric Association, 243 N. Lindbergh Blvd., St. Louis, Mo. 63141, has literature that may help. And if there is any medical problem, the advice of an ophthalmologist should be sought.

Goldberg and many of his colleagues are happy to have potential users try on contacts. But the most important thing, he feels, is follow-up care. Eyes change, lenses change, sensitivities change. He is even seeing people with a new (but correctable) syndrome that seems to come after years of wearing contact lenses without a proper checkup. Dramatically, but literally, it is this: warped eyes.