Q: Can the eye become dependent on contact lenses?

A: No. Wearing contact lenses neither improves nor worsens vision. The only “dependence” is a psychological one. The excellent vision correction provided, the convenience, and the improvement of one’s appearance make many wearers contact lens “addicts.”

Q: Why is my vision blurry while wearing eyeglasses after I remove my contact lenses?

A: This condition is called spectacle blur. It usually occurs with hard lenses and is due to corneal molding. The cornea is pliable and its shape is changed slightly by the contact lens, much as the skin of your finger becomes indented by a ring. Just as the indentation on your finger disappears after the ring is removed, your cornea gradually assumes its original shape. In the meantime you have an irregularly curved cornea causing a kind of “induced astigmatism,” for which your spectacles were not ground to correct. As a result of this temporary and artificial refractive error your vision is slightly blurry when you switch to spectacles. This situation may last from a few minutes to a few hours.

Q: Why do I see differently when I switch back to glasses?

A: See discussion of spectacle blur. Also this difference in vision may be due to the fact that spectacles for nearsightedness reduce the size of objects and those for farsightedness magnify objects (especially for aphakics, who are very farsighted). With contact lenses there is no such effect. When you switch from contacts to glasses, your brain becomes momentarily confused and interprets the smaller or larger image as blurry. Again this phenomenon is fleeting and only mildly annoying if you wear contacts most of your waking hours. Should you decide to return to full-time spectacle wear, your brain will adapt to this different way of seeing in a short period of time.

Q: Why can’t I use saliva to clean contact lenses?

A: Though the composition of saliva makes it a very efficacious wetting solution for hard lenses, it is absolutely unacceptable to use it for this purpose. Saliva contains bacteria (and possibly viruses and fungi) that are safe for the mouth, but dangerous for the eye.

Q: Can I use hard contact lens solutions for soft lenses and vice versa?

A: Absolutely not. These solutions were designed for specific types of plastic. Because hard lenses and soft lenses have very different properties, their accompanying solutions contain different ingredients. In addition soft lenses will absorb the chemicals in the hard-lens solutions; these chemicals can later be released into the eye, possibly causing irritation or ocular damage.

Q: Can contact lenses be used in sports?

A: The bony structure (orbit) that forms the eye socket was designed to protect you from injury, and it does its job extremely well. But if you’re very active in sports, for instance, hard lenses may pose problems. If you are hit directly in the eye with a racquet ball, wearing a hard contact might result in greater ocular injury than if you were not wearing lenses. That a contact lens would shatter, however, is highly unlikely: the plastic from which it is made requires the force of a hammer striking it on a cement surface in order to break it. Of course, soft lenses are safer. In some instances a contact lens can actually act as a barrier and shield the eye from scratches. However, for contact sports and racquet sports you should wear special protective glasses, goggles, or masks, whether you wear contact lenses or not.

As many see it, the main advantage of hard lenses is that when fitted properly they provide the sharpest visual acuity for all the refractive errors—even better than spectacles can. It’s not uncommon for those who have nearsightedness, farsightedness, presbyopia, and most degrees of astigmatism to report 20/10 vision—that’s better than “normal”! Your prescription can be accurately ground into the front surface of a hard lens, and its smooth, firm, domelike undersurface, combined with the tears trapped beneath, forms a perfect refracting surface for the eye. A conventional soft lens, on the other hand, conforms to the shape of the cornea much like a tablecloth drapes over a table and so cannot completely correct astigmatism originating in the cornea. There are special new soft and gas- permeable lenses capable of correcting a relatively high degree of astigmatism, but hard conventional lenses are still the best for consistently correcting the higher amounts of astigmatism; besides, not everyone can deal with the soft lenses‘ disadvantages.

LOW COST

The next most popular plus is that standard hard lenses are the least expensive of all types of lenses. When properly handled and maintained they can last ten years and more. During that time tiny scratches and roughened edges that are bound to occur even during normal wear can be polished away at minimal cost. Also, the lens can be modified for any minor changes in prescription without ordering a new lens. Should you require a new lens, the prescription can be accurately duplicated and the lens can be replaced at minimal cost. In addition, the cost of cleaning and maintaining hard lenses is quite low.

CONVENIENCE

A lot of people who wear hard lenses like the fact that they’re easy to keep clean and don’t require the sterilization and special rinsing solutions that soft-lens care entails. With hardlenses all you do is rub a few drops of germicidal solution over the lens, rinse with plain tap water, and you’re done. This is especially important if you’re a frequent traveler who doesn’t need the extra weight and bulk of several bottles of liquid sloshing around your luggage. (Not to mention the mild annoyance of a thermal disinfecting unit, which may also require a hefty electric current adaptor in some countries.) A hard lens is also easier to handle than the floppy, slippery soft lens. This is particularly true for older people. Once you have the knack, insertion and removal are a snap.

ATMOSPHERIC CONDITIONS

Since the plastic from which they are made is hydrophobic (does not absorb water), dry air doesn’t affect the quality or the comfort of the lens.

COLOR

The fact that hard lenses can be tinted almost any color does more than enhance the color of your eyes. From a practical standpoint it makes them easier to retrieve when dropped, easier to locate when decentered, and reduces the light sensitivity and glare that may occur with clear hard-lens wearing. Most often hard lenses are tinted blue, gray, or green, but other tints are available.

VERSATILITY

Hard lenses have tremendous versatility. Most standard rigid lenses are corneal lenses, which fit over the cornea only. But scleral lenses exist too. These are large contact lenses that cover the white of the eye and are used for certain prosthetic and cosmetic purposes. Fenestrated lenses, which have tiny holes drilled through them, and vented lenses, which have tiny ridges carved in the undersurface to permit a better exchange of gases, allow greater tear flow.

There are also bifocal contact lenses. Special corneal cosmetic contact lenses can be used to provide an artificial color to the eyes. They’re useful for actors and actresses and others who would like to improve or intensify their eye color. The entire lens, except for the clear, central visual area, is painted or dyed until opaque. A red-tinted X-Chrom lens is also available, which allows the color-blind to approach near normal color perception. Another type of cosmetic contact lens is completely opaque, covers the cornea and sclera, and is used to provide a new appearance for a disfigured or damaged eye.

Though the eye is quite durable, it’s also an irreplaceable, delicate, sensitive, and highly sophisticated organ. Your eye is directly connected to your brain by the optic nerve and is closely related to other systems of your body. It shouldn’t be considered independently, and before you walk off with a pair of contact lenses you should undergo a complete medical eye examination by an ophthalmologist.

Such an exam is much more than a simple mechanical test of your eye as an optical instrument. It determines what prescription you’ll need. It also determines whether you’ll be able 26 to wear contact lenses safely and comfortably, and reveals clues that form a picture of your optical health and your physical condition in general. It also yields the measurements needed to “fit” you with the right pair of lenses—these measurements must be extremely accurate if you’re going to be comfortable wearing lenses. To do all this, your eye doctor uses a variety of instruments and techniques that may seem baffling and mysterious to the potential contact lens consumer. Space- age technology has invaded ophthalmology, and your eye physician’s examining rooms may resemble the inside of a spaceship; the instruments approximate cousins of Star Wars character R2D2, with futuristic beeps and digital readouts. Whether your doctor has the latest in equipment or not, the examination can be a fascinating process if you let it; and you should feel free to pepper him with questions.

History. This first step may seem casual and unscientific, but it’s very important. Your eye doctor will ask you “Why are you here?” and discuss with you your motivation, occupation, leisure activities, systemic diseases and medications, eye diseases and medications, and allergies, complaints about your vision, whether you get headaches, and whether you’ve worn contacts before, what type they were and any problems you had while wearing them. (If you do wear contact lenses, you should keep them out of your eyes at least twenty-four hours before your exam, though seventy-two hours is preferable.)

Refraction. This step determines the prescription your lenses will need to correct whatever refractive error—nearsightedness, farsightedness, astigmatism, or presbyopia—you may have. We’ve come a long way from the days when a simple wall eye chart sufficed. Nowadays the doctor usually first instills special eye drops that dilate your pupils before using the two instruments, the Phoroptor and the retinoscope, to come up with your lens prescription.

First comes the Phoroptor, that familiar contraption that makes the examinee look like the ultimate bug-eyed Martian. As you gaze at the eye chart (projected on the wall), the physician tries out several lens combinations, repeatedly asking you “which is better, first or second?” Out of its billions of possible lens combinations, the examiner determines and fine-tunes your prescription. After this subjective test (you’re judging which lens corrects the best), the results are read off the Phoroptor in order to check the prescription by doing an objective test for refraction. As your eyes gaze at a distant target through the prescription in the Phoroptor, the doctor peers into your eyes with the retinoscope. Through the dilated pupils the light of the retinoscope creates a measurable shadow and light movement on your retina, which enables him to check the accuracy of the prescription.

Curvature of the Cornea. Using a keratometer, an optical scanning device, the ophthalmologist determines the exact “topography” of the cornea. A system of mirrors measures the horizontal and vertical meridians of the cornea. This determines the steepness or flatness of the cornea and its degree of corneal astigmatism, an important part of the overall refractive error picture, and instrumental in determining whether you need a hard or soft lens.

Muscle Range and Coordination. How well do your eyes work together? Do they point to and focus at various distances equally? How well do you judge distance and space (depth perception, or stereopsis)? To find out, the eye doctor uses a muscle light and special prisms.

Outer and Middle Layers of the Eye. Next comes the slit lamp, an electrical microscope that lights up and magnifies your eyelids, cornea, iris, lens, and fluid of your eye in order to reveal any disease, damage, inflammation, or other abnormality. A special stain called fluorescein is used in conjunction with a cobalt-blue filter to detect any corneal defects or abrasions not visible with the naked eye.

Inner Layers of the Eye. Through the dilated pupil, the retina and its blood vessels can be seen with an ophthalmoscope, which illuminates and enlarges the doctor’s view. This is the point at which early signs of diabetes, hardening of the arteries, hypertension, and other general disorders of the body can be detected.

Eye Pressure. This is the “glaucoma test.” The doctor anesthetizes your cornea with special eye drops, and measures the pressure of the eye fluid with a tonometer. Though the instrument actually touches your cornea, you don’t feel a thing because of the anesthetizing eye drops. This test is especially important for anyone over the age of thirty, although it is unusual for glaucoma to occur before the age of forty. There is also a “noncontact” tonometer which utilizes a puff of air to measure the eye pressure. Although not as accurate as a tonometer, this instrument is an excellent screening device and eye drops are not instilled.

Tear Function. Tears lubricate and cleanse your eyes and also provide the cornea with oxygen. A sufficient supply of tears is a must for comfortable contact lens wear. “Dry eyes” can be countered with special eye drops if the problem is slight. To make sure it isn’t a contraindication, the ophthalmologist performs the Shirmer test: special strips of paper placed under the lids to gauge the amount of tear production. After about five minutes the test strips are removed and the amount of tear absorption is measured and evaluated.

Visual Field. In certain instances (suspicion of glaucoma, retinal abnormalities, optic nerve disorders, neurologic disorders, headaches, and so on) a test of your peripheral vision is important. To measure your peripheral (side) vision, a special computerized instrument is used. (If you like video games, you’ll love this part of the test. If you don’t, the challenge may leave you a bit limp.) First each eye is tested separately, then together. Your head is kept immobile as you face a large dome, perforated with a scattering of pin-sized holes. As you gaze ahead steadily at a red-lit cross in the center of the dome, minuscule flashes of light go off through the holes, one at a time, at various distances from the center cross. Every time you see a “star” light up in this mini-planetarium, you hit a button; meanwhile the computer keeps score by adding up the correct “strikes.”

Your ophthalmologist will evaluate all the information thus gleaned from all parts of the ocular examination and decide whether or not you—and your eyes—are a good candidate for contact lenses, and if so, what type. Those who “pass” the exam then go on to the next step, the contact lens fitting.

Nearsightedness (Myopia). This occurs when the eyeball is too long for the lens’s focal capacity. The patient’s cornea and lens focus the image of a distant object in front of the retina, so vision is blurry except when looking at nearby objects. Myopia affects one quarter of the world and seems to be on the rise, though it’s a mystery why. Most contact lens wearers are myopes.

Farsightedness (Hyperopia). This occurs when the eyeball is too short. As a result the lens of the eye can’t bring near objects into focus by the time the image reaches the retina. (Theoretically the focal point is behind the retina.) Therefore close objects are blurry, and distant objects are clear. In mild cases distant objects are seen clearly enough so constant visual correction is not required. In severe cases distance vision may also be affected, so the hyperope needs to wear some form of vision correction constantly; these are more likely candidates for contact lenses, though the percentage is far lower than for myopia.

Astigmatism. This is a bit harder to understand. Astigmatism is a refractive error that usually results from a cornea that isn’t perfectly round, but shaped more like a football than the usual basketball shape. Imagine the cornea as a dome divided into segments by lines drawn across its surface that intersect at its center, like the segments of an orange. The normal eye, with a spherical cornea, has the same curved lines all around. The astigmatic’s  aspherical cornea has differently curved lines like one half of a lemon, with any given line either flatter or steeper than the one perpendicular to it. Therefore the vertical and horizontal components of both near and far images can’t focus together. As a result the image appears blurry. Occasionally the crystalline lens—not the cornea—is at fault in astigmatism. Astigmatism is very common and often occurs in addition to myopia or hyperopia.

Presbyopia. This is part of the aging process (usually after the age of forty) and is due to the gradual loss of elasticity of the crystalline lens of the eye. As the lens loses its flexibility, one has more and more difficulty focusing on nearby objects. You’ll know your eyes are “getting old” if your arms seem too short when you read, or if you have trouble performing close-up tasks like threading a needle. Presbyopia will occur in addition to the “Big Three”—myopia, hyperopia, and astigmatism—but pure presbyopes only require a correction during close-up tasks.

Nearly half our population has one or more of these refractive errors. Fortunately all of them can be corrected witheyeglasses or contact lenses. In nearly all cases the contact lens does it better.