Wednesday, March 22, 2023 Mar 22, 2023
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Choosing the right contact lenses
By Elliot Stendig |

MENTION THE phrase “Hey, four eyes” and a majority of the adult population will cringe. They’ve heard the phrase before; they remember the ridicule associated with it during childhood. But only those people who have been forced to view their lives through an extra pair of “eyes” attached to a plastic encasement that is strapped across the face and hooked behind the ears can understand just how potentially traumatic the experience can be: A person who really needs glasses cannot function without them.

Of course, many people are quite comfortable wearing glasses, which is fine. But 30 years ago, most people with visual malfunctions had no choice but to wear glasses-for the rest of their lives. Today, thanks to advances in contact lens technology, alternatives to eyeglass wear are extensive: Options include hard contacts, soft contacts, semisoft contacts, flex contacts, gas permeable contacts and silicone contacts. There are soft contacts that correct astigmatism, farsightedness and near-sightedness; there are even contact lenses that can correct colorblindness or change the color of a person’s eyes.

But there also are many misconceptions about contact lenses and how to properly wear them and care for them. Many people mistakenly think that prescriptions for glasses and contacts are interchangeable. Others believe that they can wear the same kind of contacts someone else is wearing. And certain TV advertisements lead many people to assume that contacts are problem-free. No mention is made of eye damage that can be caused by wearing the wrong contacts or by wearing ones that have been improperly fitted.

A recent Gallup Poll found that 5 percent (or 6.4 million) of the 128 million people who now wear glasses formerly wore contacts. The same study found that half of these contact dropouts wore their lenses for less than a year. Many of these people were victims of the “fit ’em and forget ’em” mentality that afflicts some of today’s contact lens dispensers. Different doctors have different attitudes about contact lens care. Of course, it is much cheaper to get a prescription from a doctor who takes the attitude: “Try them for 30 days. If they work, good. If they don’t, don’t call me, I’ll call you.” But 30 days is not long enough to know whether or not contacts have been fitted properly. Certain major problems can take longer than a month to develop.

And long-term follow-up care is more important than the original fit. Modifications made to the lenses during follow-up visits to the optometrist or opthamologist can prevent minor problems from becoming major ones.

Studies by leading contact lens and pharmaceutical firms reveal six main causes for dissatisfaction with contact lenses:

1. Unrealistic expectations, such asthe belief that contacts will give you instantly perfect vision.

2. Poor testing and/or fitting by doctors who also give up too soon ondifficult-to-fit patients.

3. Unsatisfactory acuity (sharpnessof vision) due, in most cases, to notbeing fitted with the best possible lenses.

4. Eye irritations and edema (swelling) of the cornea due to poor lensdesign and certain physiological problems.

5. Contact-wearer’s ignorance ofhow to take care of his lenses and eyes.

6. Poor follow-up care by doctors who think more about fitting new patients with contacts than about helping existing patients achieve successful long-term wear.

If you want contacts, to whom do you turn? Obviously, to a doctor willing to spend the time necessary not only to fit you, but also to make the follow-up adjustments as well. If the doctor delegates some of the testing and fitting procedures to assistants, you will not get the full benefit of his or her knowledge. And that knowledge is a big part of what you are paying for. But it is up to you to become informed. Ask beforehand if the doctor himself does all of the testing and follow-up care.

Most people who buy contact lenses want them for cosmetic reasons. But many people need them; contacts can improve a person’s vision and help him perform his job and sports more efficiently and safely. If you are now wearing glasses, contacts could improve your usable field of vision. Contacts also give a better quality of retinal image than do glasses. In the case of myopia (nearsightedness), contacts create a larger retinal image. And if your glasses’ refractive power (the power of prescription needed) is considerably different for each eye, contacts can create image sizes that are more uniform and closer to being normal in each eye.

Contact lenses are especially useful for persons whose jobs involve radical shifts in temperature. The temperature differences cause moisture to condense on the lenses of glasses, and the spectacles must be removed frequently and cleaned. Many people who work with cameras, telescopes or microscopes consider glasses a nuisance and an obstruction to viewing. And dancers, singers, models, actors and athletes often consider contacts indispen-sible to their performances.

Contact lenses have a much longer history than you might imagine. Leonardo da Vinci sketched and described several possible forms of contact lenses around 1508. In 1636, Rene Descartes, the French mathematician, physicist and philosopher, became the first person to suggest placing a lens directly upon the cornea with scleral contact. In 1888, A.E. Fick placed the first glass contact on an eye. And in 1947, Kevin Touhy made the first plastic corneal contact lens.

Hard and soft contacts are now familiar concepts to most people. Hard contacts are polymetryl methacrylate (PMMA), plastic lenses. The hard lenses have good optical clarity and light transmission abilities. Because of their high tensile strength, they will not break or shatter in the eye. Hard contacts also have good dimensional stability, so that their tiny, critical curvatures remain relatively constant. This stability is important to good vision. Hard contacts are nontoxic and reasonably compatible with eye tissues, but they also present a hydrophobic (water-hating) surface between the cornea and lid that hinders the passage of gases between the atmosphere and the eye. Soft hydrogel lenses, on the other hand, are hy-drophilic (water-loving). They transmit more oxygen to the cornea and are initially more comfortable.

Soft contacts also work well in such sports as football, where frequent physical encounters are compounded by dust, wind and glare. Soft contacts adhere to the eye better than do hard contacts and are therefore harder to dislodge. This extra adherence helps prevent particles from being trapped between the lens and the eye. But soft contacts have a shorter life span than do hard lenses, and they cost more.

Like hard contacts, soft contacts are made with individualized diameters, back curves, front curves, peripheral curves, center thicknesses and refractive powers. If a soft contact is not fitted correctly, however, the wearer may suffer arcuate staining of the peripheral cornea. Although this stain usually is limited to the outer layers of the corneas, it could lead, if not corrected, to irreparable eye damage. The formation of deposits on the soft contacts themselves is another serious problem. (At least a dozen different organic and nonorganic deposits have been identified.) These deposits can cause eye irritation, reduced acuity, increased frequency of lens replacement and, ultimately, dissatisfaction with soft lenses. Proper lens care can prevent some of these deposits from forming, and some of them can be removed. Protein deposits on soft contacts, caused mainly by the lysozyme found in normal tears, can, for the most part, largely be removed with enzyme cleaner treatments. But if the protein deposits are not removed, the wearer risks developing conjunctivitus (an allergic response) or giant papillary conjunctivitus, characterized by increased eye mucus, itching, reduced lens tolerance and big, irritated bumps inside the upper lid. Soft lens wearers who smoke can often wind up with pigment deposits just below the lenses’ surfaces. And microorganisms such as fungi or yeast can develop on the lenses when they are not properly disinfected. Greasy lipid deposits can be removed by daily use of the proper cleaner. But chlorhexidine, found in most cold sterilization systems for soft contacts, tends to turn the lenses yellow. And the lenses also can be discolored by the wearer’s fingerprints after he washes his hands with soaps that contain lotions or perfumes.

Proper blinking allows the contact lens to act as a pump to interchange tears behind the lens and enable a fresh supply of oxygen and nutrients to get to the cornea. In some cases, someone who thinks he is a contact lens failure becomes a contact lens success just by learning proper blinking techniques. Men average 19 full blinks per minute, while women average 14.

One of the worst things you can do to contacts before you put them in your eyes is to stick them in your mouth and wet them. There are germs in the mouth that could cause blindness.

Flex lenses, also known as semisoft contacts, actually are ultra-thin hard lenses. Their thinness allows them to bend slightly, which helps increase a tear pump action, improving the flow of oxygen to the cornea and reducing edema. The flex lens’ thinness also offers other advantages: The reduced mass dramatically lessens the lens sensation felt when blinking. And flex lenses should have better centration because of the improved capillary attraction between the posterior curve of the lens and the cornea. (The best way to demonstrate capillary attraction is with two flat pieces of glass. When both pieces of glass are dry, they easily slide apart if one is stacked atop the other. Get the two pieces of glass wet, however, and suddenly it is much harder to separate them.)

Today we have tinted hard contacts, tinted soft contacts and tinted flex lenses. But the Food and Drug Administration does not yet permit the dispensing of tinted gas permeable CAB (cellulose acetate buytrate) contacts. Instead, these new lenses are being made in the United States and exported to countries whose safety laws are not as strict as ours. But a recent study of 100 patients fitted with gas permeable CAB contacts revealed a success rate of 79 percent. And more significantly, 75 of these 100 patients previously had been unable to wear other types of contacts.

Perhaps the contacts most clamored for are the ones designed for extended wear. The actual definition of extended wear varies. Some people are happy with lenses that are safe to wear overnight in an emergency. Other people consider one week’s wear “extended.”

With hard contacts, eight continuous hours is considered a good maximum wearing time. Maximum continuous soft lens wear typically is 10 to 12 hours. Occasionally, after a patient has worn his contacts for a period of time, he reports that they feel hot. This means that the lenses are not allowing proper tear circulation between the contact and the cornea -and that modifications need to be made to prevent eye damage.

Although the FDA has expressed concern about the safety of extended-wear lenses, in 1979 it approved extended-wear soft lenses as a much-needed alternative to the intra-ocular lens (the artificial lens put in the eye to replace the clouded lens removed during cataract surgery).

You can buy extended-wear contact lenses, but they cost much more than daily-wear ones. They are more fragile and their usable life is not long. Also, you will have to go to the eye doctor more often for monitoring and adjustments of the lenses. And the chances are greater that you will develop serious eye problems from wearing them.

The silicone lens (available in hard or soft forms) is being hailed as the contact of the future. Normally, these lenses would be hydrophobic and would stick to your eyes until surgically removed. But molecular restructuring of the silicone surface provides a thin, hydrophilic outer layer that is fairly resistant to scratching.

Later this year, several new innovations in contact lenses should be announced. These innovations will include stronger soft contacts that correct astigmatism, new bifocal designs both in hard and soft lenses, lens materials that are more gas permeable, and improved contact lens care systems.

Disposable silicone contacts with ausable life of six weeks are now underdevelopment. And other throwaway contact designs are being studied. With anyluck, the cheapest of these, once they hitthe market, will not be called “pop ’em anddrop’ems.”