WHAT is transparent, plastic, roughly the Size of a pinky fingernail and can stop a basketball game when it is lost?
It's the contact lens, an object that in the last three decades has considerably increased the methods of treating eye defects and enabled patients to conceal their need for visual aid.
Actually, the idea of applying a small disk to the eye's surface is nor new—Leonardo da Vinci is credited with the original concept—but it lay dormant for several centuries until a Swiss eye doctor prescribed a glass shell in 1887 for a patient with a cancerous eyelid.
Now, almost as if to make up for lost time, refinements and innovations are being formulated so rapidly as to render the contact lens of 10 years ago obsolete and to put in the foreseeable future such developments as the lens that can be worn during sleep and for months at a time.
At present, there are two basic types of lenses—hard and soft—approved by the Food and Drug Administration, which holds a tight rein on the industry. A third product, the gas permeable lens, is now in the investigative stage.
All three lenses differ primarily in the way they allow the eye to obtain the nutrients that keep it healthy. Because the surface of the cornea does not contain blood vessels, it is dependent upon the flow of tears to.obtain oxygen and release carbon dioxide.
The hard lens is designed to accommodate that crucial need either by curvature or by being cut to leave part of the cornea exposed.
The soft lens is hydrophilic or water absorbent, so it keeps the eye bathed in fluid. Oxygen reaches the cornea in two ways: by direct passage through the lens and from the tear fluid under the lens even though it fits more snugly than the hand lens.
The third type is hard but gas permeable, which means that oxygen can pass through the material.
Each variety has its advantages and drawbacks, and the choice is based on a catalogue of factors.
The hard lens is generally considered to offer greater visual acuity.
Dr. Robert A. Koetting, contact lens chairman for the American Optometric Association, whose practice in St. Louis is confined to contact lenses, said, “The hard lenses offer better optical quality than ‘the soft. They are firm and can be polished to good standards. The soft ones bend and don't have quite the same quality of optical performance.”
Other experts said that the difference was so slight as to be almost meaningless.
For the time being, hard lenses can correct a wider range of deficiencies. Most cases of astigmatism, for instance, can be remedied only by the hard variety. A soft lens would accommodate itself to the irregular shape of the cornea and usually not correct it.
In addition, only hard lenses can now be tinted for light sensitivity and cosmetic purposes. But as more manufacturers get the government go‐ahead, experts expect that soft lenses will catch up in all areas.
Hard lenses, made of ‘a plastic called polymethyl methacrylate, are generally easier to care for, requiring only an overnight soak in a special solution and a rinse in the morning, they are more durable, and they cost less. But despite progress, they still involve an adjustment period, not necessary with soft lenses.
Dr. Morton D. Sarver, professor of optometry at the University of California School of Optometry at Berkeley and chief of the contact lens service there, said, “They are initially less comfortable, but the discomfort should not be painful or intolerable. It is poor advice for a doctor to tell a patient that he will get used to it. The break‐in period, during which the patient should wear the lenses in gradually increasing amounts of time, should take two to three weeks to attain a tolerance of 14 hours.”
Soft lenses, which must be approved by the F.D.A., were first O.K.'d for manufacture in 1971. That permit was issued to Bausch & Lomb. Another permit was not issued until 1974. Even today, only four manufacturers have approval for general purpose soft lenses. But about half a dozen companies are expected to gain approval in the near future.
The overriding appeal of the soft lens, which is made of plastic polymer called poly (2 hydroxyethyl methacrylate) is the contention that it is more comfortable. It is also said by some to give a wider range of vision because it tends to be larger than the hard lens, overlapping on to the sciera or white portion of the eye. Because it molds itself to the eye's natural curve, dust and dirt particles are less likely to be trapped under it.
“There are few failures with soft lenses,” Dr. Lawrence S. Forgacs, whose optometric practice here is limited to contact lenses and low vision therapy, said. ‘People prefer them because they are more comfortable on day‐in, day‐out basis and most want the road of least resistance.”
In addition, the soft lenses allow the wearer to be more lax about their use. Dr. Richard H. Keates, professor of ophthalmology at the Ohio State University College of Medicine, said, “Because there's no adaptation it's easier to wear them for one day not for the next three. It's perfect for the Saturday night contact lens wearer.”
On the other hand, they deteriorate more rapidly than the hard version, they are more prone to puncture and rips, and they have, until now, required a more complicated disinfecting procedure. In October, the F.D.A. granted approval to a set of three cleansing solutions, one for washing, one for soaking and one for rinsing, but before that it required that the lenses 1:1:. boiled every night in a special heating unit to prevent the growth of potentially harmful microorganisms in the soaking solution.
For those willing to wear lenses on an investigational basis, which means more frequent checkups,, there is an alternative that is said to combine properties of hard and soft lenses. Known as the gas permeable lens, the best‐known version is made of a plastic called cellulose acetate butyrate. 1.1though it does not absorb water, it does bend, according to Paul T. Russo, president of the Rynco Scientific Corporation, Floral Park, L.I., a pioneer in the lens.
Although some professionals predict it will be a major contender on the market when it is approved by the F.D.A., not all are certain of its benefits. “It's true value has not yet been determined,” Dr. Keates said.’
Asked to explain for the layman the technical difference between spectacles and contact lenses, Dr. G. Peter Halberg, newly installed president of the Contact Lens Association of Ophthamolgists, said, “Glasses alter the rays to accommodate the defect before they reach the eye. The contact lenses unite the rays inside the eye where they are supposed to unite by actually putting a new surface on the corner. They are a prosthesis floating on a layer of tears.”
Like his colleagues, Dr. Heiberg, who is director of the glaucoma and contact lens services at St. Vincent's Hospital and Medical Center of New York, said that, barring physiological contraindications or psychological resistance, contact lenses were superior to standard
Although other therapeutic uses are on the horizon, patients who have had one cataract removed and those suffering. from a gross deformity of the cornea called keratoconus can now be helped only by contact lenses.
With proper care and regular checkups ‐most doctors recommend lenses and the wearer be checked by a professional every six months, or at the minimum, annually‐there should be no long‐term danger to the lens wearer.
Dr. Sarver noted that “With the hard lenses, it is possible there may be distortions of the cornea. It all depends on follow‐up care. With proper care, they are as safe as we know. The soft lenses have only been available since 1971, but there should be no (detrimental) long‐term effects.”
Dr. Koetting noted that, since most contact lenses are fitted between the ages of 18 and 30 when the eyes don't change much, anyway, it “leads to the erroneous assumption that the lenses are responsible for something that would have happened anyway.”
Although contact lens prices vary, Dr. Halberg said he considered $200 to $350 a fair price for hard lenses. and $250 to $450 reasonable for soft lenses. Others said soft lenses stayed in the $300 range.
The fee is based not so much on the device itself but on the exacting examination, fitting and follow‐up process. Consumers are advised to ask in advance how often and for how long they can return for adjustments without additional charge. Three to six months is the norm, but some specialists include a year of service in the charge.
The specialist himself is a key component in a successful prescription. As Dr. Heiberg said, “The difference between perfection and disaster is a hairline. On a long‐term basis, an illfitting contact lens can deform the eye.”
How is the patient to find the specialist who won't cross that hairline, Dr. Sarver said, “The concerned consumer must seek the services of a fitter who is familiar with and has access to all the different lenses available. Consult with people who have been well fitted, get a recommendation from a professional society, call a university with an optometrical or ophthalmological department. Still,” he added, “the question is similar to asking how to find the best surgeon to perform an appendectomy.”
https://www.nytimes.com/1977/01/05/archives/all-about-contact-lenses-and-how-to-choose-them.html
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