In 1887, when they were first invented in Switzerland, there was one kind of contact lens, which was made of glass and covered the entire eye.
Today, there are more than 40 different brand names of contact lenses in the United States, including hard ones, not-quite-so-hard ones, soft lenses for daily wear, soft lenses that can be worn for weeks at a time, bifocal lenses and lenses with tints. As modern versions become more comfortable, more effective and more popular, choosing among them becomes more complicated.
''The ideal contact lens is one that is well tolerated, that you see well with,'' said Dr. Jorge Buxton of the New York Eye and Ear Infirmary. ''It's not going to be the same for everyone. There's not one answer. There are multiple answers.''
Experts estimate that 18 million people wear contact lenses, less than 20 percent of the 120 million Americans who need vision correction. That figure is expected to double to 35.5 million in the next five years.
The cost of the examination, the lenses and the follow-up visits is usually included in one package price, which can range from $150 to $300 for both hard and soft lenses. Glasses cost about $35 to $100 for the examination and about $35 to hundreds of dollars depending on the lens required and the frames desired.
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Esthetics and Convenience
Most wearers choose contact lenses for reasons of esthetics or convenience. ''I was too vain to wear my glasses and I would just squint all the time,'' said Diane Asadorian, who works for CBS and who began wearing soft lenses seven years ago.
''There are a thousand reasons why I would never go back to glasses,'' she said. Among them are the fact that lenses don't bounce on her nose when she goes running, don't block her view of the ball when she plays tennis and don't fog up in the rain. And, she said, they make her eyes look bigger.
Although these advantages may be universal, the ability to wear contact lenses is not. Most people are able to wear some kind of lens, said Dr. Harold Davis, a Chicago optometrist and chairman of the contact-lens section of the American Optometric Association, but not all people can wear the same kinds of lenses.
''The perfect lens differs from person to person,'' he said. ''Many lenses may be acceptable but there is only one optimal lens for each person.''
Difference in Materials
The biggest difference between the types of lenses is what they are made of. The oldest of the contact lenses now available are hard contacts. They were originally made of glass but are now commonly made of a plastic called polymethyl methacrylate.
These lenses are gradually being replaced by a second type of hard lens, known as a rigid gas-permeable lens. The newer lenses, made of a mixture of silicone and plastic, are more porous and more comfortable. They do not bend easily and can still be used if they accidentally dry out.
Soft lenses, in contrast, are made from a material that looks like thick cellophane but is mostly water. They bend and stretch, and if left in the air away from water or tears for even a short time, they become brittle and unusable. The newest form of soft lenses are extended-wear lenses, which can be worn for weeks, sometimes months, at a time.
Other variations include tinted lenses that can enhance the color of light eyes and may soon be able to change the color of dark eyes, and bifocal lenses that are still in the introductory stages. Some companies are now experimenting with extended-wear hard lenses as well.
The material used in the lenses is often the determining factor in who can wear each type. Traditional hard lenses are thought to be the least comfortable, particularly in the beginning, and are most often worn by people who cannot wear softer lenses - for example, people with severe corneal astigmatism (in which the cornea is irregularly shaped) or those who have had certain types of eye surgery. The rigid gas-permeable lens is more comfortable, but the silicone tends to produce a surface that smudges easily.
Therefore, said Michael Binning, a Washington optician who specializes in the fitting of contact lenses, ''Most people who can wear soft lenses do wear soft lenses.'' Because they are thinner and more flexible, they can often be tolerated by people who find hard lenses painful.
There are problems with soft lenses as well, however. Though they can be worn by people with some degree of astigmatism, vision for such people may not be as clear as it is with hard lenses or glasses. Soft lenses also trap protein and calcium deposits from tears and must be replaced as frequently as every year. Hard lenses, in contrast, usually last two years and have been known to last much longer.
Advantages and Disadvantages
Extended-wear lenses must be replaced more often. Those who can wear them say that between cleanings they often forget they have a vision problem - people can sleep and swim in these lenses, keeping them in for as long as a month at a time.
But those who have dry eyes, severe allergies or protein-laden tears often cannot wear these lenses, and even those who can wear them are usually advised not to keep them in indefinitely.
Dr. Davis, for example, advises patients to wear the lenses for no more than a week between cleanings.
Extended-wear lenses are useful, he said, because they allow more oxygen to reach the eye, but ''I tell my patients that records are for athletes, not contact-lens wearers,'' he said. ''You can wear your contacts for 30 days without removal, but would you wear your underwear for 30 days without removal? The eye is a very dirty place.''
Fitting a patient for hard lenses is only slightly different from fitting a patient for soft lenses. In most states only an ophthalmologist or optometrist can do so, though several states allow opticians to examine patients and prescribe contact lenses.
In the first visit, the shape of the eyeball and the patient's vision are measured. Hard lenses must usually be ordered from the manufacturer; soft contact lenses are often on hand.
For people who choose hard lenses, therefore, a second appointment is necessary to fit the lenses and teach the patient to care for them. A patient is usually told to wear new lenses no more than six hours on the first day, increasing that time by an hour each day for a week. Most doctors will want to see a patient at the end of the week and from four to six times over the next 90 days.
Those who choose soft lenses are also instructed on the use of their lenses and are asked to return within a week or two for a follow-up visit. Those who choose extended-wear lenses are usually told to take the lenses out each night before the follow-up visit. They are then allowed to wear the lenses overnight and are examined the morning after and during several follow-up visits.
Different people adjust differently to contact lenses. Some have no problems with comfort or vision, while others say that their eyesight is blurry and that they can feel the lenses in their eyes. Usually these symptoms disappear. Sometimes they do not.
Once the adjustment stage is over, most of the responsibility of caring for the lenses rests with the wearer. The contacts must be cleaned and stored carefully, following the specific instructions of the eye-care specialist. Many problems with lenses are caused by the poor hygiene habits of the wearer, according to Constance Oliveras, an administrator at the contact lens clinic at the New York Eye and Ear Infirmary, which instructs people on contact lens care.
''They don't clean their hands before handling the lenses,'' she said, ''or, instead of going to the sink to rinse them with saline they put them in their mouth and then in their eye. Then they come to us with eye infections.''
Other common mistakes, she said, are made by people who wipe their eyes too hard and unknowingly take out their lens with the tissue, and those who let lenses slip down the drain of the sink during insertion.
The other major problem faced by contact lens wearers are unrealistic expectations, Dr. Buxton said. ''Your body is never the same every day and your eyes are never the same,'' he said. ''They respond to stress, strain, allergies, food intake, alcohol intake. You have to expect contact lenses to feel different when their environment is different.''
https://www.nytimes.com/1985/01/05/style/buying-contact-lenses-new-world-of-choices.html
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