The poor vision brought on by keratoconus is due to a highly exaggerated form of astigmatism that is poorly corrected by glasses. Until contact lenses became available, keratoconus patients often had to be satisfied with partially corrected vision and led less-than-normal lives. But contact lenses can provide almost perfect vision in most cases and are the best means of vision correction for this disorder.

Hard contact lenses are usually used because the smooth, dome-shaped shell plus the tears beneath it provide a new smooth, round refracting surface for the eye. Because the cornea is diseased, the eye may not tolerate conventional hard lenses. In that case gas-permeable contact lenses may be prescribed instead. Soft contact lenses, in general, do not work well with keratoconic eyes. As is the case with astigmatism, the pliable material from which they are made conforms to the misshapen cornea, duplicating the refractive error. Soft contact lenses may, however, correct a portion of the faulty vision. And in some cases the patient is fitted with hard lenses on top of the soft lenses, piggyback fashion, to take advantage of the comfort of the soft lens plus the sharp visual acuity provided by the hard lens. In all cases the lenses are difficult to manufacture, and the fitting process must be extremely exact to achieve acceptable results.

Eye practitioners can test you if you suspect you are color deficient. Telltale signs include a lack of interest in colors, choosing color combinations that don’t appeal to most people, a preference toward blues and yellows and indifference toward reds and greens, unawareness of fall foliage, difficulty in seeing veins and freckles, and the preference of black-andwhite TV over color.

In the past there was nothing available to improve color blindness. But several years ago Dr. Harry Zeltzer developed a special, red-tinted contact lens that improves the color perception of those who suffer the most common type of color blindness (red-green). (A red-tinted lens in eyeglasses doesn’t work because the lens is too far away from the eye.) The X-Chrom lens has been a godsend to people whose jobs and interests require the ability to identify colors. Telephone repairmen, hunters, drivers, home handymen, painters, cosmeticians, printers, textile workers, chemists, photographers, artists, decorators, and anyone who selects clothes (even if it’s just their own)—all can benefit from this type of lens. It has even helped color-deficient children who were wrongly labeled as learning deficient.

The X-Chrom lens is deep red in color. Only one tinted lens is prescribed, usually for the nondominant eye. It works by changing the relative intensities of red and green objects. The nondominant (corrected) eye supplies the brain with information about colors that are normally hard for it to identify; the dominant (uncorrected) eye continues to supply the colors the eye is capable of seeing correctly. As if by magic the wearer sees colors he never even knew existed. At first colors may seem to glow or be more vibrant, and objects that used to blend into the background may seem to jump out. But the eye and brain soon adjust to the unfamiliar information: the newly perceived colors are identified and learned.

If necessary the X-Chrom lens can be manufactured to incorporate a prescription to correct refractive errors. In that case the wearer keeps his regular clear lens in the dominant eye and the X-Chrom corrective lens in the other. Usually a third, clear contact lens incorporating the necessary prescription is kept on hand for use in the nondominant eye when the X-Chrom is not worn. Those who do not wish to wear a contact lens in both eyes can wear glasses over the X-Chrom lens.

The fitting, adjustment period, wearing, care, and handling of the lens are the same as for conventional hard lenses, but the cost is higher. The X-Chrom may be worn during both daytime and nighttime, but many elect to remove the lens at night because of the reduced illumination that will be exaggerated with this lens. Some wearers experience a slight reduction in visual acuity, or their depth perception is affected because the two eyes receive unequal amounts of illumination. Cosmetically the red color of the X-Chrom lens is very obvious. All these disadvantages must be weighed against enhanced color perception. The color-blind patient, therefore, has to be well motivated in order to wear this lens.

Clearly the X-Chrom offers no guarantees and is not for every color-deficient patient. In the words of its developer it’s “an aid, not a cure.” But for most color-blind people it means improved color perception and opens up new vistas in everyday pleasures and work.

Daily-Wear Contact Lenses. Conventional hard lenses, gas- permeable lenses, and soft lenses can be worn to correct vision following a cataract removal. But the problem of daily insertion, removal, and cleaning is a real one, and discourages many a potential daily wearer. Fear of inserting a foreign object into the eye; diminished dexterity; reluctance to handle tiny, delicate, almost invisible objects—all can add up to a less-thansuccessful scenario. The replacement rate with soft lenses is particularly high: the average life span of a pair is two years because of loss, torn lenses, or lens deposits. Because of their advanced age aphakes often have dry eyes, and soft lenses require a more lavish tear supply than do hard lenses. Also, loose lids, usually found as a product of aging eye, can cause fitting and wearing problems.

Many aphakes do, however, adjust to life with daily-wear contact lenses. Sometimes a willing friend or relative helps with the lens care and handling. Aphakes also have some distinct advantages to mitigate their particular problems when it comes to contact lens wear. Since the cornea has been cut (and nerves severed) during the cataract extraction, the eyes are less sensitive and contact lenses feel more comfortable. (Unfortunately this desensitization may mean that the aphake is less aware of any injury and damage to the eyes; therefore these patients require careful monitoring.) For those who can’t cope, there are two more alternatives: extended-wear contact lenses, and intraocular lenses.

Extended-Wear Contact Lenses. As discussed previously this is a recent development, and many eye practitioners feel that these lenses are the safest alternative. As such they have become the single most frequently prescribed form of contact lenses for aphakes. And with good reason: extended-wear contact lenses are comfortable and provide good visual acuity. Primarily they solve the biggest drawback of aphakic contact lens wear by eliminating the daily insertion, removal, and cleaning required of all other types of contact lenses. In fact, extended wear for aphakes was FDA approved before extended wear for so-called “cosmetic” use because of the very real and greater need for this type of lens.

Extended-wear contact lenses are initially inserted at the doctor’s office and worn continuously for up to one month or more. During periodic eye examinations at the doctor’s office the lenses are usually removed and cleaned and then reinserted. As with daily-wear lenses, sometimes a neighbor or a relative is enlisted to help remove, clean, and insert the lenses between office visits.

Extended wear does have its drawbacks. The lenses currently available will not fit everyone, but they are successful in an estimated 75 percent of the aphakic population. Since they wear them for longer periods of time, aphakes tend to have even more of a problem with protein deposits than normally occurs with the daily-wear lenses. The useful life of the lens is thus shorter, necessitating frequent replacement, though the “saline eyewash” has been shown to be an effective preventive that can be used without removing the lens. Wearers should be hygiene conscious and be willing to go to the doctor for the needed follow-up visits.

Intraocular Lenses. Although they are not contact lenses, plastic intraocular lenses are quite similar and offer a viable and permanent solution for the aphake. Each year a larger percentage of those who undergo cataract removal will have a lens implant, usually at the time of cataract surgery. As a result they have a new substitute lens built right into the eye; quite often vision is restored to 20 / 20 without glasses. This is the most convenient form of cataract correction, since the lens is never removed unless complications ensue.

The intraocular lens is the brainchild of the English ophthalmologist Harold Ridley, who developed the idea during World War II. He saw wounded RAF pilots with fragments of Plexiglas windshields embedded in their eyes. The plastic remained inert, which led him to the conclusion that intraocular lenses could be made from the same material (polymethylmethacrylate, or PMMA, the same plastic from which conventional hard contact lenses are made) and safely placed into the eye.

Since ophthalmologists do not know the long-term effects of intraocular lens implants, the best candidates for ocular implants are the elderly. If they have dry eyes and eyelid abnormalities, which preclude wearing contact lenses, the lens implant will be the best type of vision correction. On the other hand those who are very nearsighted, have detached retinas, poorly controlled glaucoma, diabetes, or other eye diseases, are advised to seek the other vision-corrective devices mentioned earlier.

About 10 percent of the intraocular implants result in complications. Many of these can be corrected without removing the implant. They may include dislocation of the implant, changes in the cornea, inflammation of the iris, retinal detachment, and increased pressure in the eye that could lead to glaucoma. At times the intraocular lens will have to be removed. Tests are still being conducted to study the longterm effects of intraocular lenses.

Future developments in this field lie mainly in the improvement of the lenses themselves. Another method of vision correction involves grafting “live” contact lenses onto the aphake’s cornea. Donor corneas are frozen and ground to size, then sutured onto the living host cornea. To date several such operations have been successful.

Canada, Australia, and Europe enjoyed several types of extended-wear contact lenses several years before we did. However, there is no Food and Drug Administration in those parts of the world, and because of this lack of strict monitoring control and quality, these lenses have posed a health problem, especially as related to corneal complications.

At first the only type of extended-wear lenses that the FDA approved were therapeutic bandage lenses worn on the cornea and the sclera for use in treating certain eye disease. However, the potential of these lenses for correcting refractive errors was soon realized, and eventually the FDA allowed a few contact lens manufacturers to produce extended- wear corneal lenses. A handful of qualified ophthalmologists and optometrists were then permitted to fit and investigate the extended-wear lenses as visual corrective devices.

They were approved for wear by aphakes since they have a pressing need for an alternative to the often unsatisfactory spectacles and available contact lenses. After five years of rigorous testing by a select group of ophthalmologists (of which I was one) and optometrists on a specially selected group of volunteer patients, the first two brands of extended-wear contact lenses were approved for general cosmetic use: Perma-Lens, fabricated from perfilcon A, a terpolymer, and made by Cooper Vision; and Hydrocurve II, composed of the polymer bufilcon A, and made by Continuous Curve, Inc., and Revlon.

The reaction of the eye to extended contact lens wear is even more important than in daily-wear contact lenses. The lenses must allow plenty of oxygen to reach the cornea because the cornea does not have the same opportunity to recover from prolonged oxygen deprivation as it does with daily-wear contact lenses. In addition, during sleep the eyelids are closed so the ocular physiology is different: there is no available oxygen from the atmosphere and there is an absence of oxygen- filled tears. The semirigid gas-permeable lenses would logically seem to fit the bill for optimum oxygen supply, but studies so far have revealed drawbacks in these lenses during prolonged wear. Except for the pure silicone lenses used by aphakes, the contact lenses that have been FDA approved to date for extended wear are all soft, and made of plastics similar to those from which conventional soft lenses are made, but modified to yield greater oxygen permeability. The rate of oxygen-carbon dioxide transmission through the lens material is determined by two major factors: the water content and the thickness of the lens. The higher the percentage of water contained in the lens material, and the thinner the lens, the more gas is exchanged. A very thin, very highwater-content lens, however, has so far proven to be too fragile to be practical. Thus, a lens manufacturer can take either of two roads to maximize gas transmissibility. It can design a relatively thick lens with a high water content (Perma Lens), or a very thin lens with a lower water content (Hydrocurve II).

Extended-wear lenses are therefore from 55 percent (Hydrocurve) to 75 percent (Perma-Lens) water. Conventional daily-wear soft lenses are on the average about 30 to 40 percent water. The Hydrocurve extended-wear contact lens is as thin as a single strand of hair (0.05 mm).

Oxygen transmissibility is not the only factor in lens wear, however, and thickness and water content not the only variables. The different materials have different properties, and there are different diameters, edge designs, and other design factors to be considered. For instance, the lower the water content of a lens, the higher the tensile strength it has, and the less it tends to accumulate deposits and support the growth of bacteria and fungus. This can mean a longer useful lens life, more comfort, and less frequent replacements. Lower water content yields a slightly more rigid lens, which generally provides better visual acuity. On the other hand the higher the water content, the softer will be the lens and the more comfortable it may feel. But the higher the water content, the more important it is to have adequate tear flow, since the tear flow is essential to keep the lens hydrated. Thinner lenses are more apt to fold and tear and are more difficult to handle. Also, it may be difficult to determine whether they have inverted or not.

Even with more than one brand to choose from, it is impossible to predict whether someone will be able to wear contact lenses for an extended period of time. The cornea and tear composition of each person are different, as is the tendency to form protein deposits and the ability of the eye to adapt to life with less oxygen and a diminished tear pump. It is up to the doctor to weigh the obvious benefits against the possible risks to the health of the eye. Now that extended wear has been FDA approved, any eye practitioner can dispense them, regardless of how much (or how little) experience he has had with them. This is the most promotable form of contact lens wear by far, and the media exposure can sometimes paint too pretty a picture, giving the consumer unrealistic expectations. It is especially important to have a highly experienced ophthalmologist monitor the health of your cornea during extended contact lens wear. True success comes only with strict supervision. Patients must understand the importance of compliance with a strict follow-up schedule of numerous eye examinations, during which subtle changes in the eye may be discovered, indicating that extended wear must be stopped.

Any sign of a problem (red eyes, reduced vision, discharge, or irritation) should be reported to the doctor at once and the lenses should be removed immediately. Reinsertion of the lenses should occur only after your doctor has made certain that your eyes have returned to their normal, healthy state.

Because oxygen and carbon dioxide can pass directly through the material, the lenses can be worn in comfort for relatively long periods of time with no adverse effects on the cornea. Because the cornea can “breathe” better with these lenses than with conventional hard contact lenses, you have an easier break-in period. There is less chance of the overwear syndrome occurring; less corneal edema occurs (eliminated completely in some wearers); and the reduction in spectacle blur allows you to switch easily from contacts to glasses. There is less of the increased sensitivity to light which may occur with hard lenses.

Greater comfort and longer full-time wear are a boon to every hard-lens wearer but are especially important for those people with special visual defects such as aphakia or keratoconus (misshapen cornea), which can often be satisfactorily corrected only with hard lenses. Such people depend upon their contacts to a much greater extent than those who wear contact lenses for cosmetic purposes.

Because oxygen goes through the material itself, these lenses don’t have to be as small as the hard lenses to enhance oxygen supply to the cornea. Though the size is a factor in the overall fit and comfort, gas-permeable lenses are often slightly larger in diameter than conventional hard lenses. This increase in lens surface gives you better night vision (when the pupil dilates) with none of the annoying—and possibly dangerous— halos or flare that plague the hard-lens wearer. Since the larger diameter makes the lens edge fit under the upper lid, there’s less likelihood of the lens falling out.

You are also able to wear these lenses part time—only socially, or casually—the same as with soft lenses, thus saving them only for weekends, evenings, or other special occasions. Irritation from foreign objects such as dust from the atmosphere is less of a problem with these lenses than with standard hard lenses. This is due to the thinness of the lens, which allows it to cling more tightly to the cornea and to the fact that the lens covers more of the cornea. Of course, at all times, the lensrides on a thin layer of tears.

Have found hard lenses uncomfortable, but are unwilling to give up their sharp visual acuity.

• Would like a contact lens that approaches soft-lens comfort, but cannot wear soft lenses because of astigmatism or “dry eye.”
• Like the idea of increased wearing time, but cannot wear soft lenses.
• Can’t handle soft lenses.

• Can wear soft lenses but don’t like the inconvenience involved in the care.
• Are interested in the possibilities of part-time lens wear, but can’t wear soft lenses.

Imperfect Vision Correction

Soft contact lenses were once thought to be the perfect contact lens but this is not now the case. Some soft-lens wearers eventually have to switch to hard lenses or gas-permeable contact lenses. The major reason for soft-lens dropouts is the less-than optimal vision that the lenses provide. There are several reasons for this:

Because the soft lens conforms to any irregularity of the corneal surface, the cause of astigmatism is duplicated on the outer surface of the pliable contact lens. Conventional soft contact lenses can only correct small amounts of astigmatism, and a large number of those who were fitted with soft lenses were happy with the comfort but had to settle for less-than perfect vision. (Special soft tonic lenses have since been developed, which definitely improve vision; however, they are not perfect and they cost more than conventional soft lenses.)

Soft lenses are not “custom made” the way hard lenses are, and a precise prescription can’t be “carved” exactly into the surface of the lenses. A contact lens specialist has to choose from standard sizes and available prescriptions, which may result in a less-than-perfect fit for those with in-between prescriptions. And if a lens needs to be replaced, it isn’t always possible to reproduce an exact duplicate of the required lens. In the latest state of the art of contact lens production, whether lathe-cut or spin-cast molded, lenses are available, like a shirt- collar size, only in certain powers, sizes, and curvatures. Also, during hydration the exact power of the lens may be altered slightly. In spite of constant checks and rechecks some lenses of inexact power may slip through. Your physician, however, should be able to detect any deviation from the prescribed power.

Visual clarity may also be erratic. During every blink the soft lens flexes, creating a moment of blurred vision. Also the constant lid pressure on the contact lens can distort the lens surface so that vision is adversely affected. (This is especially noticeable when reading. Also, when doing close-up work, one tends to blink less often and soft lenses become less hydrated than is optimal. The lens hardens slightly and reduces visual acuity.) Likewise, any change in the humidity will affect the water content of the lens, and thus its clarity. Low humidity leads to a drier, less comfortable lens and hence poorer vision.

Inconvenience

Another complaint is that the care and handling of soft lenses are more complicated and time-consuming than that of hard lenses. They must not only be cleaned, they must also be disinfected daily, as a separate process. Unlike hard lenses, you can’t just rinse them in tap water after cleaning. You must have a bottle of saline solution for this purpose. A once-weekly soak in a special enzyme solution is also recommended.

Travel can be a problem for soft-lens wearers. The bottles of solutions you need to carry with you are bulky and take up valuable luggage space. If you use the heat method of disinfection, you have an extra (albeit small) item to carry and there is always the problem of finding a compatible electric current. Some countries will necessitate your buying and bringing along an adaptor. There’s also a special “foreign” cord, and manufacturers are experimenting with battery-operated heating units. Chemical disinfection is the alternative, but a small percentage of people will develop an allergic reaction to these solutions.

You may find soft lenses more difficult to handle than hard lenses because they’re so flexible and slippery when wet, and almost invisible. Their very softness and pliability, which is so desirable in the eye, makes them more difficult to feel with your fingers. In addition, because of their size and malleability, some people find them harder to insert and remove.

It is obvious, though, that preserved saline minimizes the possibility of patient error and is more convenient (there’s nothing to mix). It definitely inhibits the growth of bacteria and fungi, so there’s no need to replace it with a fresh batch every day. I have found that approximately 20 percent of my patients eventually become allergic to the preservatives in this type of saline, but for the remaining 80 percent preserved saline is highly effective and has no side effects. If a patient should develop an allergic reaction, I merely switch him to the unpreserved solution.

Premixed Unpreserved Saline Solution. To solve the dilemmas posed by the other two forms, a third type of saline now exists. Sterile, premixed, preservative-free saline in vials or packets is available to satisfy the cautious and / or sensitive few who can’t tolerate the preservatives but who like the convenience and want to reduce the risk of possible bacterial contamination. Unfortunately, saline in this form must necessarily be packaged in small, individual doses to be opened, used, and discarded daily. (Once opened the packets are no longer sterile, the way Band-Aids are contaminated upon opening, but can safely be used for up to twenty-four hours.) That makes this form even more expensive than the preserved solutions—and it is not as widely available. The small packets, however, travel well to the office, or farther from home. On trips you can transport the exact amount of saline you need, and discard the empty packets as you go along.

Using Saline Solution. To clean the lens with preserved or unpreserved saline, a simple method is to place the lens in the palm of the hand and fill the cupped palm with saline. Rub each side with the index finger of the other hand for twenty to thirty seconds. Then rinse with more saline.

To rinse the lens with saline after cleaning, disinfecting, or enzyming, place the lens in the palm of the hand or hold it between index finger and thumb. Direct a steady stream of the solution at the lens using either the entire packet or equivalent (about one ounce) for both lenses. Be generous with the saline; this is not the place to skimp. Rinsing will remove potentially harmful agents that could adversely affect your lenses and your eyes. After heat sterilization the lenses may be kept stored in the case in which they were sterilized, covered with saline solution, until you’re ready to insert them. As a precaution, you should disinfect the lenses if you’ve left them in saline for more than a few days.

A lens with embedded deposits will be uncomfortable, less pliable, permit less oxygen to pass through, and result in reduced visual acuity. If stubborn deposits cannot be removed with the conventional cleaning and enzyme methods, I recommend that my patients use either fine table salt or baking soda along with saline solution. Put a few drops of saline in the palm and add a pinch of the salt or soda. Place the dirty lens in the salt bath and rub gently with the index finger of the other hand for a few minutes. You can safely perform this cleaning method once a week if needed. Admittedly this is a last-ditch effort; the method may prove fruitless and a new lens may have to be ordered.

Cleaning Solutions

The very characteristic that makes soft lenses so comfortable —their ability to absorb moisture—is a two-sided coin. Unfortunately soft lenses will also absorb just about everything else they come into contact with, including cigarette smoke, deposits from your own tears, makeup, and aerosol sprays such as deodorants, room fresheners, hair sprays, etc. If these deposits are not removed daily, when still “fresh,” they may harden and lead to cloudy, damaged lenses that will be uncomfortable and unable to correct your visual defect properly. Lenses badly cared for will need to be replaced more often than those that are kept scrupulously clean. I often see patients in my office with “spoiled” soft lenses—full of deposits that they failed to remove, marred by pits and cracks, or tainted with bacteria. Once deposits have taken hold, they become embedded in the lens material; even if they could be removed, the lens would be left pitted.

Special soft-lens surfactant cleaning solutions are meant (but not guaranteed) to remove surface deposits. In addition to detergents they contain preservatives to inhibit the growth of microorganisms, and cushioning agents that keep the lens from becoming damaged during the rubbing. In all cases the mechanical rubbing plays a very important role in the effectiveness of a surfactant cleaner.

To use the cleaning solution, apply a few drops to each surface of the lens and either rub between your index finger and thumb or massage in the palm of your hand with the index finger of the other hand. Rub each side for at least twenty seconds, making sure you clean the outer edges as well as the center. Make sure the lens is well hydrated before applying the cleaning solution. Always rinse off the cleaning solution thoroughly with saline because it can leave a film that will eventually cloud the lens, especially if you use thermal disinfection afterward. Any deposits or impurities on the lens can be permanently baked into it by the heat method. Therefore it is imperative that the lens be absolutely clean before heating. Studies have also shown that a dirty lens absorbs more preservatives than a clean lens, another reason for thorough lens cleaning before storage and disinfection.

All soft lenses have one thing in common: the ability to absorb water like a sponge. This is what makes them soft and sets them apart from their firmer cousins. In the hydrated state soft lenses contain anywhere from about 30 to 80 percent water, which they get from the solutions you use and from the tears in your eyes. These water-loving lenses have the consistency of a gel, rather like firm, clear Jell-O. They’re very pliable and elastic; and can be turned inside out, bent, twisted, and stretched. Yet they have a “memory” and can spring back to their original shape while maintaining the same correct prescription and fit. (This type of treatment is not recommended, however.) While they’re in your eyes, soft lenses drape themselves over your cornea like a tablecloth, unlike rigid lenses, which have no such “give.”

The various soft lenses differ in their water content, thickness, design, type of material, and method of manufacture. Each lens has its own set of fitting guides with certain advantages and disadvantages, and the eye practitioner must weigh all the factors carefully in relation to your eyes before deciding upon the best lens for you. You may be able to wear one type of soft lens and not another; in fact this situation is quite common. For example, the greater the ability of a lens to hold water, the better the oxygen transfer and the softer and more comfortable it may be. This type of lens will not be comfortable, however, on an eye that doesn’t have a sufficient tear supply in order to keep the lens fully hydrated. Additionally, this type of lens might not provide sharp visual acuity. Soft lenses with a lower water content offer better visual acuity and usually have a longer life span, but are not quite as comfortable as those with a higher water content.

Like the hard lens, the soft lens also has its counterpart, the ultra-thin lens. Incredibly, this lens has a center thickness of less than 0.05 mm. Although they are more comfortable, these lenses are not for everyone because they are more difficult to handle and usually vision is not as clear as with the thicker standard soft lenses.

Another distinguishing variable feature of soft lenses is their size—they’re considerably larger than hard lenses in order to stay centered on the cornea. From 11 to 16 mm in diameter, they are designed to fit over the cornea, the limbus (the junction between the cornea and the sclera), and part of the sclera as well.

Who Should wear Soft Contact Lenses

The decision to fit you with soft contact lenses rests between you and your contact lens specialist. In general you’re a likely candidate if you:

• Are most interested in comfort and want a contact lens that you can wear for a long period of time every day.
• Have been unsuccessful with hard contact lenses.
• Live, work, or play under conditions that are dusty and / or windy.
• Want to wear contacts intermittently, not full time.
• Are athletically inclined, especially if you water ski, snow ski, or play tennis or contact sports.
• Are not overly concerned with extremely sharp vision.
• Do not have a large amount of astigmatism.

Soft lenses‘ raison d’être can be easily summed up in one word: comfort. If hard lenses can be compared to a new pair of shoes, soft lenses seem to fit like an old pair of broken-in sneakers. Many wearers claim they don’t feel a thing, and are completely unaware of them from the word go. Hard-lens wearers who had previously given up on these lenses are especially astounded by the lack of eye sensation because they have something with which to compare the soft lenses. No wonder more than half of all the new contact lenses that are sold are soft! And the percentage is increasing, although not quite as fast as a few years ago.

The soft revolution in contact lenses began over twenty years ago in Czechoslovakia, when chemist Otto Wichterle began experimenting with a plastic called HEMA (hydroxyethylmethylmethacrylate). HEMA had been used in surgery because of its compatibility with human tissue; it seemed to be a good candidate for contact lens material because it was also optically clear. Working in his kitchen with equipment he constructed from his children’s Erector set, Wichterle concocted the first soft contact lenses. After testing was completed, more efficient and sophisticated production lines were set up. The rest, as they say, is history. The new soft lenses seemed like a cure-all—the lenses were comfortable, and in most cases the vision was good.

New Developments in Soft Contact Lenses

The first soft lenses became available in the United States in 1971. To say there have been some changes made since then would be an understatement. The original and still highly popular Bausch & Lomb Soflens was (and still is) spun-cast of good old HEMA. But the field of soft contact lenses is a lively, dynamic, ever-changing one, with new lenses constantly coming into the market. There are now dozens of brands—numerous types of plastic whose chemical ingredients roll trippingly off the tongue (2-hydroxyethylmethacrylate, N-[1, 1-Dimethy1-3- oxobutyl]-Acrylamide and Methacrylic acid is an example). These plastics differ entirely from the synthetic material of hard contacts. Unlike PMMA, which is basically comprised of a single monomer (a substance made of low-weight molecules), soft, or hydrogel, contact lenses are made of various polymers (compounds of high molecular weight derived by combining many smaller molecules, such as monomers). These polymers, most of which are still based on HEMA, are made from a selection of at least eight different components, plus several “crosslinking” agents that bind the polymers together. The physical properties of hydrogel materials resemble living tissue more than any other class of biosynthetic material. Various methods of manufacture have also been developed, including lathe-cutting (the plastic is ground while in a hardened state) and mold-casting.

The impetus for all this ongoing activity springs from the remaining imperfections of the soft contact lens. Although a remarkable breakthrough, the soft lens is by no means a cure- all and cannot be worn by everyone. Thus the drive for improvement continues. For example, the industry is making significant headway with astigmatism and bifocals, heretofore huge flies in the ointment as far as contact lenses were concerned. The new soft toric lenses enable soft-lens wearers with appreciable amounts of astigmatism to see more sharply than with traditional soft lenses. (However, they still do not provide the crispness of vision that a hard lens can provide.) In the fall of 1981 soft bifocal lenses first became available to the public. For those who can’t achieve normal levels of comfort, wearing time, and visual acuity with soft lenses, super-thin soft lenses may be the answer. Another improvement involves a special coating that retards the accumulation of protein deposits on the soft lens’s surface, while improving the water-retentive properties. Such deposits are a major factor in shortening the life of soft contact lenses.