A. If they are, something is wrong. Contact the fitter at once.

Q. Can you tell that someone is wearing contact lenses?

A. Usually not.

Q. Can they be coloured?

A. Yes. Lenses can be tinted almost any colour.

Q. Is that expensive? A. No.

Q. I’m worried about lenses slipping round behind my eyes. Does this often happen?

A. No, never, It’s impossible!

Q. I need glasses for reading only. Would I be suitable for contact lenses?

A. No. Stick to your glasses.

Q. I have astigmatism. Does this mean I can’t wear contact lenses?

A. Not at all. Hard lenses cover astigmatism. It is even possible to have special soft lenses for astigmatism.

Q. What is spectacle blur?

A. Temporarily blurred vision in glasses after wearing contact lenses.

Q. Is that serious?

A. No. Not unless very severe and persistent.

Q. What causes it?

A. Either a moulding of your corneas into a new shape, or a slight swelling from accumulation of fluid in the corneal outer layer.

Q. My friend wears very thin, hard lenses. Is that a good idea? A. The smaller the better, so long as they give good vision.

Q. She says she never gets spectacle blur. Why is that?

A. Very small lenses are less liable to cause this, because the corneas have a better oxygen supply.

Q. Why is oxygen important?

A. Corneas, like all living tissues, need oxygen to survive. As they can’t get it via the blood because they do not contain blood vessels, they have to get it direct from the atmosphere.

Q. What happens if I get a bit of grit behind a contact lens? A. You will know all about it. This doesn’t happen often.

Q. What should I do?

A. Take out the lens and wash it.

Q. But suppose the grit stays in my eye?

A. Get someone to remove it with the corner of a clean handkerchief, or see your doctor. Don’t use your lenses meantime.

Q. Is it very difficult to insert and remove contact lenses?

A. The difficulties in insertion are largely psychological. Removing lenses is easy, but it takes a bit of practice to learn todo it quickly.

Q. Is it a good idea to use a rubber sucker to remove lenses?

A. No. Not unless you can be certain that the lens is on the cornea.

Q: Can contact lenses harm the eye?

A: Contact lenses are dangerous if you have a faulty lens, or do not maintain proper ocular hygiene, or don’t follow the recommended wearing and handling procedures. For instance, corneal abrasion can occur when the lens isn’t inserted properly. Corneal edema occurs if you overwear the lens. An eye infection may be caused by fingers or contact lens solutions that are contaminated. And foreign bodies can sneak under the lens and irritate the cornea.

With regard to the vast number of contact lens wearers, though, such complications have been remarkably rare.

Q: What is corneal edema?

A: It is the most common contact lens complication and the main reason you can’t wear lenses for twenty-four hours (except for extended-wear contacts). Edema means swelling, which is what happens to your cornea when you wear your lenses too long and deprive the cornea of oxygen. Even though gas-permeable lenses, soft lenses, and lenses that allow optimum tear exchange reduce the chance of edema, there is always less oxygen than normally reaches the naked eye. You’ll know when you’ve been wearing your contacts too long: your eyes will burn, turn red, be light sensitive; maybe you’ll see halos or rainbows around lights. Unless you’re too stubborn or highly motivated, the most appealing thought in the world will be that of removing your lenses, which is exactly the right thing to do. In minor cases your cornea will recuperate in a few hours (better yet—overnight). If you really overdo it, recovery may take several days and corneal abrasion may follow.

Q: What is conjunctivitis?

A: This is an infection of the conjunctiva, the mucous membrane that covers the white part of the eye and lines the underside of the eyelids. Conjunctivitis and other eye infections can afflict the contact lens wearer who doesn’t clean (and disinfect, in the case of soft lenses) his lenses according to instructions. It can also occur when wearers clean and wet the lenses with saliva, which is loaded with bacteria, viruses, and perhaps fungi. In addition to the ordinary garden-variety conjunctivitis (”pink eye“), there’s another form called “giant papillary conjunctivitis,” which is caused only by contact lens wear (the contact lenses themselves, deposits on the lenses, or any of the contact lens solutions). In treating the individual with this type of conjunctivitis I discard the contact lens and prescribe a steroid (cortisone) eye drop. Resolution of the disorder may take days or even weeks. Once the conjunctiva has healed, I order a new lens and then instruct the patient to use different solutions. For the hard contact lens wearer the correct solution is determined by trial and error. For the soft contact lens wearer I permit only the use of unpreserved saline and the heat method of disinfection. Happily, this type of conjunctivitis, when treated properly, rarely recurs. If it does reappear, cessation of contact lens use may be the only solution.

Q: What’s corneal abrasion?

A: Corneal abrasion is the term used when the surface layer of the cornea is scraped or scratched off. This can occur when you wear the contact lenses too long (overwear syndrome); with improperly fitted lenses; or by inserting, removing, or recentering the lens improperly. Sleeping with daily-wear lenses on often leads to corneal abrasion. The symptoms are decreased vision, burning pain, sensitivity to light, the sensation of having something in your eye, and copious tearing. Abrasion that follows corneal edema may not be evident until hours after the contact lenses have been removed. Healing is mercifully rapid: usually within thirty-six hours. You may take aspirin for the pain, and cold compresses may help. Consult your ophthalmologist to make sure there are no complications; he may also recommend that you wear a tight eye patch for the duration of the recuperative period to keep the eye immobile. Though most cases of corneal abrasion are minor, a severe infection can invade the damaged cells. While this is unlikely to occur, it is a possibility, so don’t treat corneal abrasions lightly.

Q: Can contact lenses cause drooping of the eyelids?

A: It’s rare, but the results of one study indicate that in a very few cases, contact lens wear can lead to a condition called blepharoptosis, resulting in eyelids that appear to droop. All the patients studied had been wearing hard lenses, some for many years. The researchers’ most likely explanation is that the condition was caused by excessive manipulation and rubbing of the eyelids, usually because of difficulties in inserting and removing the lenses. The trauma caused eyelid muscle damage. This condition can be corrected surgically.

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.

Adjustment and Wearing Tips

Day 1
Two periods of two hours each with the lenses in place.
Day 2
Two periods of three hours each with the lenses in

place.
Day 3
One period of five hours.
Day 4
One period of six hours.
Day 5
One period of seven hours.
Day 6
One period of eight hours.
Day 7

One period of nine hours.

Continue adding one hour of wearing time each day until a maximum of sixteen hours is reached. If you wish to exceed the limit your practitioner has given you, make sure you get his permission.

Even though these lenses permit more gas exchange than conventional hard lenses, by rights they should be called semi-gas permeable because, except for those made of pure silicone, they still don’t allow 100 percent transmission of gases. Thus overwear can still occur, with its attendant edema, discomfort, and spectacle blur. Those for whom the lenses are exceptionally comfortable —even right away—are particularly in danger of being lulled into a false sense of security. In addition, the percentage of oxygen that reaches the cornea is lessened when the lenses become coated with mucus and deposits. Accumulation of protein deposits is one annoying habit that gas-permeable silicone lenses share with soft lenses. So is the tendency of CAB lenses to absorb undesirable substances such as cosmetics, hair sprays, and small amounts of the preservatives contained in the solutions used in their care.

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.

Cleaning with a surfactant cleansing solution and disinfecting may not remove all the deposits that cling stubbornly to the lens surface. To remove these deposits a special enzyme solution is used; this “digests” and dissolves lens proteins much the same way the enzymes in your body help break down protein.

You should use the enzyme cleaner once a week to help prevent buildup of protein deposits. (To help you remember, perform this procedure on the same day every week—the first or the last day, or every Wednesday, etc.) Once deposits are established, they will increase and can pit the lens surface, leaving it damaged even after it’s purged of the accumulations. Enzyming is especially important for those who tend to produce tears heavily laden with protein. Factors such as air pollution, makeup, and eye irritation increase production of this protein.

The enzyme tablets come in a starter kit, which also contains two vials for mixing and soaking (one for each lens) and a “lens retriever” to help remove the lenses from the solution. After using up the starter tablets you can buy the tablets from your doctor or pharmacy and keep using the original vials and retriever.

To use the enzymatic cleaner follow the informative circular that the manufacturer provides with the package. Though the instructions suggest simply rinsing the lenses with saline before submerging the lenses in the enzyme solution, I would recommend that you use cleaning solution and rinse off the lenses thoroughly with saline. Also, instead of dissolving the enzyme tablet in distilled water, you may use premixed saline solution if you don’t have distilled water on hand.

If you are allergic to the chemicals in preserved saline, I still recommend enzyming the lenses once a week and using the heat method of disinfection. If the chemicals in the enzyme cleaner affect your eyes, you can leach the lenses by soaking them in pure, unpreserved saline for several hours after enzyming.

Soft Contact Lens Lubricating Solutions

Soft lenses are generally more comfortable than hard lenses. But an eye that’s even slightly dry can cause soft-lens discomfort. To restore adequate moisture you can instill a drop or two of saline solution while wearing the lenses. Or you can use one of the special lubricating solutions formulated for contact lenses. These will clean, lubricate, and cushion the lenses while they’re still in your eye, and may be used as often as needed. Decongestants, which are not formulated for contact lens use, contain chemicals that may be absorbed by the lenses and are definitely to be avoided. Never use any eye drops not recommended by your doctor while you are wearing soft contact lenses.

Soft Contact Lens Mechanical Cleaning

Mechanical cleaning (massaging the lens with saline) is very important to maintain the integrity of the lens. If this procedure is omitted, a light filmy deposit will form on the lens, especially if it is heat disinfected. The lens will eventually become less comfortable, less transparent, and allow less oxygen to pass through it. In just a few weeks the lens will have to be replaced. Mechanical cleaning, therefore, is integral to every soft-lens wearer’s regimen. For some wearers, however, it is the only method recommended for cleansing their lenses.

The surfactant cleaners, chemical disinfecting solutions, and preserved saline solutions all contain chemicals that the soft plastic lenses can absorb and then release into the eye. About 20 percent of soft-lens wearers are allergic to preservatives and therefore should not use the solutions that contain them. Usually switching to nonpreserved saline solution and thermal disinfection will solve the problem.

Such was the case with one of my patients. She had been using the cold disinfection method for a few months with no problems. One day she walked into my office with red, itchy, irritated eyes and a whitish ocular discharge. After purging her lenses of the chemicals, I placed her on a strict, no-preservative regimen that utilized a mechanical cleaning method, an unpreserved saline solution that she mixed herself, thermal sterilization, and once-a-week enzyming. Every day she removed her lenses, placed them one at a time in the palm of her hand, and placed several drops of the saline on the lens. She then massaged the lens with the index finger of her other hand for at least one minute to remove the accumulated dirt. After rinsing the lens with nonpreserved saline, it was ready for heat sterilization. This procedure has proved so successful, I now prescribe it for most of my allergic patients.

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.

A soft lens has a gellike consistency, and this “forgiving” quality allows it to conform to the cornea almost perfectly. Its larger size and soft edges mean the eyelids glide smoothly over it—instead of bumping into it—during each blink. The tenacity with which it clings to the cornea prevents foreign particles such as dust in the air from slipping under the lens, a major cause of irritation for hard-lens wearers, especially in polluted areas or on windy days. Because of its clinging nature, it is also less likely to pop out.

Soft lenses are soft because they absorb water, which allows for the gas exchange that is so important to the health and comfort of the cornea. The cornea, which has no blood vessels of its own, gets its oxygen and releases its carbon dioxide directly through the air or through the tears. The soft-lens material itself is only slightly gas permeable; however, it is the tears contained in and around the plastic that allow air and carbon dioxide to pass through. Therefore more oxygen is supplied than with conventional hard lenses, which do not absorb water. A greater supply of oxygen also means that soft lenses can be commonly worn for fourteen hours or longer without harming the eye, since the overwear syndrome occurs less frequently. Though the gas exchange is better than with hard lenses, it is still below the normal rate that you find in the naked eye. Therefore it is possible for overwear to occur eventually.

Another difference between hard lenses and soft lenses is that soft lenses do not increase the eye’s sensitivity to light. This reduction in photosensitivity is due to a reduction in eye irritation.

Finally, the very term soft is a psychological plus, and puts many a leery lens wearer at ease.

Wearing Flexibility

Soft lenses are not only physically flexible—their wearing time is flexible too. With rigid lenses you must follow a strict wearing schedule as you gradually build up to your maximum tolerance; then you have to stick to that full-time schedule daily. You can’t casually skip a day or cut down a day or two without undergoing some readaptation. With soft lenses it’s an entirely different story. You don’t have to follow quite such a strict adaptation schedule. You’ll probably be able to wear your contacts all day a week after you’ve gotten them.

And you can wear your lenses intermittently and change back to glasses whenever you want. For instance, if you wish you can wear them a few hours each day; or wear them just during the weekend and then return to a full-day wearing schedule without any adverse effect on the eye. You can even wear them for special occasions such as for playing sports or for social events without any harm to the eye.

Another factor that makes soft contact lenses fully interchangeable with glasses is that there’s no corneal molding because of the plastic’s softness. That means there’s no annoying “spectacle blur” when you decide to wear glasses, and the oxygen deprivation and corneal edema that cause spectacle blur are less likely to occur.

Safety

Because of its large size, a soft contact lens acts as a “transparent bandage” that covers and protects the eye from hazards such as contact-sport injuries and foreign particles in the atmosphere.

It’s extremely rare for a soft lens to pop out of the eye. No matter how rugged your sport, you can relax, confident that your lenses are safely clinging to your cornea. You can even swim while wearing soft lenses, as long as you don’t dive or open your eyes too wide. The especially daring even may risk a quick dive below the surface, provided the eyes are shut tightly to prevent the lenses from floating off. I’ve heard of hard lenses being recovered from the bottom of a pool, but with a soft lens miracles such as this never happen. Wearing protective goggles is a good solution for those who want to see where they’re swimming, but these must fit very well in order to prevent chlorinated water from seeping in and being absorbed permanently by the lens plastic. Salt water is nothing more than a strong saline solution similar to the tears and special rinsing solution you use in cleaning soft lenses. Therefore it does no harm if you accidentally get some in your eyes while swimming in the ocean. The chlorine in pool water, however, does pose a problem because of the tendency for soft lenses to absorb such chemicals. Therefore I recommend that my patients remove their lenses before entering a pool. It is advisable to irrigate the eyes with fresh water or saline solution after leaving the pool and before inserting the lenses. Snorkeling and scuba diving are possible, too—but again, the fit of the mask must be carefully made to avoid water entering the eye, possibly causing the lenses to decenter or even float off.

You can even take a short nap while wearing soft lenses, which can be a lifesaver in some situations. Overnight sleeping is completely taboo; however, catnaps with soft lenses in places do no real harm, as long as you don’t make a habit of it. Your eyes might feel a bit dry and murky upon awakening, but instilling a few drops of saline solution will restore the lens and the eye to their previously compatible relationship.