Forty-four cases a year of any disorder, even a potentially blinding eye infection, do not often set federal officials worrying. But when those cases represent a doubling of the rate of infection in five short years, and when it is traced to a medical device used by millions of Americans, even 44 cases grab their attention.

That is why headlines were made this month when a link was established between the corneal infection called Acanthamoeba keratitis and soft contact lenses.

Just 75 cases of Acanthamoeba have been reported to the Centers for Disease Control in Atlanta since the infection was first identified in 1973. It is unusually virulent and usually does not respond to antimicrobial drugs; most cases require corneal transplants.

The 44 cases occurred between June 1985 and August 1986, when the CDC became alarmed enough to begin a case-control study. Of this group, according to Dr. Jeanette Stehr-Green, who directed the CDC study, 83 percent wore contact lenses, and 75 percent wore soft contact lenses.

The report sent a chill through the ranks of contact-lens wearers. More than 20 million Americans use contacts every day. Since the first wearable lens was marketed 50 years ago, the industry has mushroomed, with annual sales of $1.3 billion and a smorgasbord of products that includes hard lenses, soft lenses, daily-wear and extended-wear lenses, custom-made and off-the-shelf lenses, lenses that can change eye color with or without vision correction, lenses that hold up for 20 years and, just introduced last week, lenses that are made to be disposed of and replaced every seven days.

They are designed for people who are nearsighted and who otherwise would need spectacles to get around. They have been refined to aid the farsighted as well -- either with bifocal lenses or by wearing two different lenses, one for distance vision and one for near vision -- and to correct the corneal imperfection known as astigmatism. And they are a boon to cataract patients, the young as well as the old, who without contact lenses must wear bulky spectacles to compensate for the lens that was surgically removed.

For most people, the contact lens combines high fashion -- have you ever seen a model with glasses? -- with high-tech vision, enabling wearers to see better and look better.

Yet as the numbers of users go up, and as popping in a lens becomes as ho-hum as brushing your teeth, the incidence of problems connected with contacts is likely to rise.

The rate of serious complications is low -- less than 1 percent -- but eye specialists are concerned over the increase in corneal disorders, primarily infections and ulcers, that have been linked to contact lenses.

The problem seems to be not so much in the lens itself as in the way it is used. According to health officials, contact lens wearers tend to run into problems when they wear their extended-wear lenses for too long a stretch, when they are sloppy about disinfecting their soft lenses, or when they allow their hard lenses to become scratched and dirty.

In the recent government study of the rare Acanthamoeba infections, Stehr-Green and her colleagues compared the habits of 27 infected soft lens wearers with those of 81 non-infected controls who also wore soft contact lenses. Two differences emerged: infected individuals were four times as likely as controls to rinse their lenses in a homemade solution rather than a commercially packaged one, and they were twice as likely to wear their lenses while swimming.

"In general, care given to contact lenses by patients and controls was poor," noted Stehr-Green, pointing out that 96 percent of the cases and 81 percent of the controls "deviated from the routine contact lens care procedures recommended by the manufacturer."

All lenses need to be rinsed regularly in a saline solution. Commercial rinsing preparations, sold in 12-ounce bottles and left open for several weeks, usually contain preservatives that fight the growth of bacteria and fungi. Homemade rinses are made of store-bought distilled water and a pre-packaged salt pill, and while the solution is concocted one day's worth at a time, the water -- usually sold by the gallon -- might stay open in the bathroom for months.

Because the distilled water is not sterile, homemade solutions may often become contaminated. "Only one of the 59 commercial preparations we studied had any bacterial contamination," said Stehr-Green, "versus 11 of the 11 homemade solutions." Two of those solutions, she said, were infected not only with yeast and bacteria but with the Acanthamoeba amoeba as well.

Acanthamoeba keratitis is difficult to detect, often mimicking more common infections such as herpes. It causes pain so severe that, according to Stehr-Green, one individual chose to have the infected eye removed rather than continue suffering.

Sometimes, even the more routine treatment -- corneal transplant -- is not enough. If traces of the amoeba remain in the eye, the new cornea can become infected as well, and a second or even a third transplant might be required.

Some ophthalmologists think the incidence of Acanthamoeba keratitis is actually much higher than professionals realize. "There's no doubt in my mind that there probably are twice as many cases, maybe more," that the CDC doesn't know about, said Dr. Perry Binder of San Diego, immediate past president of the Contact Lens Association of Ophthalmologists.

"I myself have seen six cases," he said, "and I haven't reported any of them to the CDC." Complications: Mild to Serious

The CDC study adds one more to a growing list of the potential hazards of contact lenses.

Most of the hazards occur to the cornea, the transparent covering of the iris and pupil on which the contact lens rests. A soft lens sits directly on the cornea; hard lenses and rigid gas-permeable lenses float on a thin layer of tears.

Contact lens-related corneal problems include irritation, swelling and scratching, which tend to be transient, and infection and ulcers, which are more severe. The milder conditions usually can be traced to an ill-fitting lens, a piece of dirt trapped under the lens, or a lens that is itself scratched or torn. The eyes itch, burn and redden, and the best treatment is removal of the lens for a few days. If the lens is damaged or poorly fit, it needs to be replaced.

More serious problems like ulcers and infection may begin with many of the same symptoms -- eye discomfort, excessive tearing, vision changes and redness. Should these occur, the lenses should be removed immediately until an optometrist or ophthalmologist can examine the eye.

Some 21 million Americans now wear contact lenses, up from 14 million in 1980. More than half wear soft contact lenses -- about 11 million of them daily-wear soft lenses, another 3.5 million extended-wear. The rest wear lenses that are inflexible, either plastic hard lenses or the new gas-permeable lenses made of a rigid polymer, which, like the polymer used in soft lenses, allows extra oxygen to reach the cornea.

With the prices of lenses steadily dropping, and the incidence of nearsightedness steadily rising, the number of people who use contacts will no doubt continue to increase.

To gain a better understanding of the risks of serious eye problems, a contact lens industry group, the Contact Lens Institute, is about to begin a study in collaboration with the Massachusetts Eye and Ear Infirmary examining records of 50 to 75 infected contact lens wearers and another 100 to 200 non-infected controls. The cases will include persons infected with Acanthamoeba amoeba and Pseudomonas bacteria at eight major eye centers around the country, according to Dr. Kenneth Kenyon, coordinator of the study and associate chief of ophthalmology at Massachusetts Eye and Ear. Kenyon expects preliminary results within six months.

As for the Food and Drug Administration, the agency's new Corneal Ulcer-Contact Lens Task Force, under the direction of Dr. Richard Lippman, is said to be considering a warning label for contact lens packages and letting the public know that the FDA thinks wearing soft lenses, especially extended-wear lenses, may be risky.

The Hard and the Soft

Part of the confusion for consumers stems from the fact that contact lenses come in several varieties.

Hard lenses, the granddaddy of contact lenses, were introduced in the 1930s and now are worn by about 1.5 million Americans. They are difficult to fit and painful to get used to, gradually changing the shape of the cornea and sometimes causing corneal calluses and abrasions.

On the positive side, old-fashioned hard lenses are easy to care for. They tend to create the sharpest vision of all contact lenses, and, if properly cleaned and occasionally polished, can last for 20 years.

According to Dr. Michael Lemp, professor and chairman of the Center for Sight at the Georgetown University Medical Center, prolonged use of hard lenses may cause harmful changes in the deep layers of the cornea. "Changes have been observed in the shape of cells and even in the number of cells that are associated with a decrease in the vitality of the tissue," he said. But just how -- or whether -- those changes would translate into vision problems is not yet known, he said.

A new kind of rigid lens -- the gas permeable lens -- looks like a hard lens but is thought to be less traumatic to the eye. These lenses are made of a plastic that allows more oxygen to reach the cornea, thus minimizing the chances of corneal swelling or scarring.

Many vision care professionals consider these to be the contact lenses of the future. They estimate that within 10 years, one third of contact lens users will be wearing rigid gas-permeable lenses, up from some 20 percent today.

Soft lenses come in two forms: one form must be removed each night, the other may be worn for days or even weeks at a time. Extended-wear lenses essentially are identical to daily wear lenses, except that they are thinner and made up of a higher proportion of water. They allow a greater amount of oxygen to reach the cornea -- but, because they are so porous, they can harbor and hold bacterial infections far more easily.

Soft lenses, by far the most popular form of contact lens, are worn by about 15 million Americans. Daily-wear lenses currently outsell extended-wear lenses nearly four to one. Both kinds are so easy to fit that they are sold at drug and department store chains, often available "off the rack" in stock sizes.

The new DuraSoft tinted contact lenses, which can change anyone's eye color, are not only being sold cheaply -- they are also being sold to people who don't need glasses, but just want the fun of looking like they were born with blue, green, aqua, gray or hazel eyes. This adds to the fast-spreading impression that contact lenses are a cosmetic device to be used, and even shared, as casually as mascara.

The mass marketing of contacts means some wearers may receive poor instruction in lens care, which could be one source of infection, vision care specialists say.

"Ophthalmologists like me see a disproportionate number of problems coming from patients who purchased their lenses at high-volume, low-chair-time outlets that tend to discount their services," said Lemp. He added that in the past year, as more eye infections have been reported, these chains seem to have become more rigorous in their education techniques.

The very quality that makes soft lenses so comfortable -- their ability to absorb water and allow plenty of oxygen to reach the eye -- is also the quality that makes them susceptible to harboring bacteria. That is why they must be scrupulously cleaned {see box, Page 17} and, according to some physicians, taken out when the wearer is swimming, using aerosol sprays, or, with daily wear lenses, sleeping.

Another risk of soft lenses, according to Dr. James Karesh of the University of Maryland Eye Care Center, is the development of deep blood vessels in the cornea, which normally has no blood vessels. Karesh said vascularization usually can be traced to improper fit. The blood vessels disappear after the lenses are removed for several days and the eye patched so it can rest, he said.

Convenient -- and Risky

To many eye specialists, the most controversial contacts are the extended-wear soft lenses. These lenses, which are approved by the FDA to be worn for as long as one month without being removed, have been associated with various eye infections and corneal ulcers.

The problem with extended-wear lenses is that they can deprive the cornea of the oxygen it needs to function, especially during sleep.

When a non-lens wearer closes his eyes in sleep, only about one-third of the daytime level of oxygen reaches the cornea, according to California ophthalmologist Binder. And when an individual sleeps wearing contact lenses, the amount of oxygen reaching the eyes is cut in half again.

Used improperly, Binder pointed out, extended-wear lenses reduce the amount of oxygen available to the cornea to such low levels -- one sixth of the daytime level -- that the eye's metabolism converts from aerobic (with oxygen) to anaerobic (without oxygen). This means the eye starts producing lactic acid, a byproduct of anaerobic metabolism, which Binder said can damage the cornea and increase the eye's susceptibility to infection.

To get enough oxygen to the eye, Binder said, contact wearers should keep extended-wear lenses in for no more than six days, and then sterilize them overnight to give their eyes a chance to breathe. He said this should reduce the risk of corneal damage to almost zero.

Meanwhile, according to Lippman of the FDA's Division of Ophthalmic Devices, extended-wear lenses seem to be largely responsible for the most important risks of contact lenses. He said the FDA received 135 reports of corneal ulcers associated with contact lenses in 1986, up from 35 the previous year, and most of those were in extended-wear lens users.

"Preliminary data compliled by the FDA," Lippman wrote in FDA Consumer, "suggest that users of extended-wear contact lenses have a greater chance of developing corneal ulcers than people who wear other types of contact lenses."

Ulcers, or eruptions, on the surface of the cornea often are caused by various infections. The severity of infection depends on the organism that causes it. One of the most serious is the infection caused by the Pseudomonas bacteria, "which have an increased tendency to adhere to the surface of the contact lens," said Lemp. "With an extended-wear lens, you are placing the bacteria there and leaving them there, where there is little oxygen and little tear exchange, for a period of weeks."

Pseudomonas keratitis leads to pain, itchiness, redness and irritation. Although the infection is more responsive to medication than is Acanthamoeba, if it is not caught early enough it could, like Acanthamoeba, cause enough corneal damage to necessitate a transplant.

Lemp said he no longer recommends extended-wear lenses for his patients. The only exceptions he makes are for elderly post-cataract patients who have trouble removing the lenses on their own.

Not all experts are so critical of extended-wear contacts, especially since many of the problems are associated with improper fit or inadequate cleaning -- not with the lens itself.

Binder, for example, is more sanguine about this type of lens. "They do stress the epithelium, or top corneal layer, of the eye," he said, but if they are cleaned thoroughly once a week and left out overnight, "they can be a highly successful mode of vision correction."

A number of extended-wear rigid lenses are just becoming available. These gas-permeable lenses are expected to avert some of the problems of soft extended-wear lenses because they allow a greater total level of oxygen to reach the cornea, both through the lens material itself and under the lens in the tear layer on which it floats.

These lenses, such as the new Paraperm, "are less likely to accumulate waste products" than soft extended-wear lenses, said Dr. Perry Rosenthal, an ophthalmologist at the Harvard Medical School, because of that tear layer. "Each time you blink," he said, "the lens pops up and gives the tears a chance to wash it."

Other lenses under development allow so much oxygen to reach the cornea that they are almost like wearing nothing at all. According to Dr. Fred E. Goldberg, a McLean optometrist, two new organic contact lens materials -- collagen, which is the same substance that the cornea itself is made of, and fluorocarbon -- are "so different from any of the plastics now being used for contact lenses that they're in a class by themselves."

Rigid fluorocarbon contact lenses, for instance, let 99 percent of oxygen travel to the cornea, he said, compared with some 60 to 70 percent for the best of the plastic lenses.

Goldberg predicted that within the next year fluorocarbon lenses will be available for extended-wear use, and within two years soft collagen lenses will be available for disposable use. He said the collagen lens now used in Europe has an important advantage over the disposable lens recently introduced in this country: it disintegrates after a week or two in the eye. This makes it impossible to wear it longer than intended.

What Price Vanity?

No one ever said looking beautiful was easy -- or even risk-free. Liberation from heavy spectacles obviously has its price, from the added expense of the lenses and solutions, to the hassles of traveling with contact lens paraphernalia, to the trauma of searching frantically for a dropped lens in the most unlikely places. What long-time lens wearer doesn't have a story of losing, and often finding, that precious piece of plastic on a wind-swept beach, down the drain of a public restroom, or under the front tire of a parked car about to drive away?

Hassles and hardships are one thing; impairment or loss of eyesight is quite another. That is why the reports of Acanthamoeba infections in contact lens wearers have commanded the attention they have. No one is willing to go blind for the sake of vanity.

Contact lens experts stress, however, that most users have nothing to worry about. The consensus among vision care professionals is clear. With careful attention to how lenses are worn, and how they are disinfected, the 20 million Americans who now opt for invisible vision correction may continue to do so with confidence.

Still, that confidence must be mixed with caution. "Eye doctors are stressing that patients should not treat contact lenses as innocuous cosmetic items," noted Lippman of the FDA, "but as the medical devices they are."