The lens functions basically as a protective shield and prevents a damaged or ailing cornea from coming into contact with the eyelids and the air. Healing is thereby accelerated and pain is alleviated for as long as the lens is worn, which is on an extended basis (more than twenty-four hours). As such it can take the place of the tight eyepatch formerly used to immobilize the eye to facilitate the recovery process. It is usually needed only temporarily until the condition being treated has cleared up. The lens is placed on the cornea by the ophthalmologist and is removed by the doctor when the disorder being treated has been cured.

Uses of Bandage Lenses

The lens has been used for many years with varying degrees of success to treat a great number of conditions. The most frequent uses are for:

Dry Eyes. Although I have cautioned against the use of a soft lens when tear production is reduced, this lens plays an important role in severe cases of dry eyes. The dry-eye syndrome is a common by-product of the aging process and affects women more often than men. In postmenopausal women all the mucous membranes begin to dry because of the shift in hormone production. In these cases dryness of the eye can become quite severe. A dry eye may also be caused by drugs (birth control pills, antihistamines, and so on), injury to or infection of the lachrymal glands, autoimmune disorders (Stevens-Johnson syndrome), severe injuries or infections of the eye, and vitamin deficiencies.

Eyes with a marked reduction in tear production can lead to damaged corneas. For patients suffering from dry eyes a bandage lens in tandem with frequent instillation of artificial tears is an excellent treatment. The eye drops are absorbed by the highly hydrophilic (water-loving) lens, bathing the eye with them in a more constant fashion than if drops alone were used.

Bullous Keratopathy. As a result of the aging process or following injury to the eye, which may be accidental or occur after intraocular surgery such as cataract extraction, the cornea may swell with an abnormal amount of fluid. The inner surface of the cornea (endothelium) becomes damaged, vision becomes blurred, and there is marked pain. The bandage lens can reduce and sometimes completely alleviate both symptoms by protecting the eroded corneal surface and by acting as a barrier to prevent fluid from escaping from the cornea.

Corneal Ulcers and Abrasions. The bandage lens seems to accelerate the healing process in abrasions and ulcers that can result from viral, bacterial, and fungal infections. This form of treatment should only be used in conjunction with antibiotic, antiviral, or antifungal eye drops.

Trichiasis. As a result of an injury, infection, or aging, the eyelashes may turn inward and rub against the cornea. A bandage lens can act as a shield while (or until) the primary condition is treated.

Chemical and Thermal Burns. By eliminating the constant irritation of the eyelid coming into contact with the healing corneal tissue, a bandage lens allows the cornea to grow back normally and more rapidly. Using a bandage lens postoperatively after a burn increases the success rate of such surgery.

Penetrating Corneal Wounds. When the cornea becomes wounded, a bandage lens aids in forming a protective shield and can be employed to facilitate healing when surgery has to be delayed.

Bell’s Palsy. When the upper lid is unable to close completely, the cornea may become overly dry. The bandage lens protects the cornea, but frequent instillation of artificial tears is necessary as an adjunct.

The “Contact Lens” as a Drug Deliver System

There now exist tiny discs containing special medication that may be placed on the eye to provide a constant source of medication. The small oval-shaped flexible “lens” is worn over the sclera under the eyelid. Its sole purpose is to act as a reservoir for drugs in liquid form, allowing specific amounts to be released into the eye gradually over a prolonged period of time. It’s really a time-release capsule for the eyes. The drug in use is, therefore, more effective than when it is administered as intermittent drops, because constant, round-the-clock treatment is possible. Also lesser amounts of the drug may do the job with this method. This can in turn reduce the local and systemic side effects and allow the use of more potent drugs such as steroids and glaucoma medication. Once in place the “contact lens” is a convenient way of administering medication, particularly for patients who might not otherwise comply with the prescribed treatment. Ocusert, containing the glaucoma medication pilocarpine, and Lacrisert, containing lubricating medication, are the two special “lenses” now commercially available. They can be worn continuously (even while sleeping) and removed and replaced weekly for the duration of the treatment.

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.

Astigmatism is not corrected quite as well as it is with conventional hard lenses. However, vision is appreciably sharper than with soft lenses, even the toric soft contacts.

Gas-permeable lenses are more expensive than hard lenses; they cost even more than conventional soft lenses. But since they are nearly as durable as hard lenses, replacement is less frequent. The lenses can, however, be chipped and scratched. Warping may occur with time, though damage is minimized with proper handling. CAB lenses can be stained by eye makeup and hairspray. The surface deposits that form easily on the silicone lenses can’t always be removed completely with the usual cleaning and soaking solutions. This is less prevalent with the CAB lenses.

The lenses are difficult to make and delivery time may take a few weeks. The right lens cannot be dotted to avoid confusing the right and left lenses.

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.

For a long time, tinted soft lenses were not available in this country because of lack of FDA approval. Because the lenses are large and extend beyond the iris onto the white part of the eye, a complete dark tint would also look rather odd. But the transparency of a nontinted lens makes it difficult to see, especially when dropped. The advertising campaign based on the soft lens’s near-perfect resemblance to a drop of water is no exaggeration. No tint also means no glare reduction, but since photosensitivity in soft-lens wearers is relatively rare, this is a minor disadvantage.

However, this ban may no longer be an issue for soft-lens wearers, because in June of 1981 a tinting process for soft lenses was made available. The physician may send any FDA approved soft contact lens to a special laboratory in North Carolina in order to be tinted according to certain specifications.A 1.5 mm border and a 4 mm diameter central zone are left clear in order for the lens to appear normal on the eye and to correspond to the pupil. The remaining “iris” area is then tinted, using a special process that permanently bonds the color to the lens. Because the inner surface of the lens, that part that comes in contact with the cornea, remains free of the tint, the process is in compliance with the FDA regulations. In addition, the color is safe, will not leach out, and holds up under either chemical or heat sterilization. Any color (blue, green, brown, etc.) may be specified, in intensities varying from 10 to 30 percent. Later that year Ciba Vision Care obtained FDA approval for their light blue Softint lens. Tinted soft lenses may become the rule rather than the exception.

Dry Eyes and Air

Those people with inadequate tear production are poor candidates for contact lenses in general, but especially for soft lenses. The drier the eye, the harder the lens should be; therefore someone with moderately dry eyes may be able to wear hard lenses successfully, but not soft. When a soft lens dehydrates in the eye, the edges may harden and curl away from the cornea, causing discomfort and possible lens fallout. Anywhere the air is dry—the desert, an airplane, an air-conditioned or heated home or office—will adversely affect hydration and thus the comfort of the lens. One of my patients kept returning to my office complaining of red, itchy eyes and frequent popping out of his soft lenses. I finally determined that the office in which he worked had an extremely efficient air- conditioning system and consequently the air was very dry. I couldn’t change his job, but I did recommend he try two procedures: that he blink more frequently, and that he instill lubricating eye drops frequently during the day. Both these procedures combined to solve his problem. During air travel the low humidity within the airplane may cause you discomfort, in which case you can simply remove your lenses and switch to eyeglasses.

Always wash and dry your hands before handling the lenses. Prepare your work area, be it sink or tabletop. Establish your routine and then stick to it to avoid mixing up the lenses. It’s advised that you always start with the right lens. I place a tiny dot on the rim of the right lens of my patients to allow them to distinguish it from the left lens and to banish the right-or-left problem forever. Whenever you rinse your lenses with water, be certain the water is cool. Never use hot water.

Hard contact lens solutions

Proper contact lens care includes using the proper solutions. These all play different roles in making contact lenses more comfortable and safer to wear. Essential solutions are wetting, cleaning, and soaking solutions, though you may find you occasionally need to use a lubricating solution while the lenses are in place. As is the case with the lenses themselves, the standards for hard-lens solutions are set by the American National Standards Institute. These standards apply to the solutions‘ functions, labeling and packaging, sterility, and the tolerance of the eye to the solutions.

Wetting Solution. Essentially, this turns a hydrophobic lens surface into a hydrophilic one that’s readily kept wet by the tears. It coats the lens surface and helps prevent any bacteria and dirt on your fingertip from being transferred onto the lens during insertion. It also provides a liquid cushion between the lens and the eyelid, and the lens and the cornea, making the lens more comfortable.

Cleaning Solution. This solution removes the dirt, oil, protein, and any other residues that have built up on the lenses during normal wear. If you don’t remove these particles regularly, they will collect in the micropores of the plastic, making your lenses less comfortable and less optically clear. Always rinse off the cleaning solution thoroughly with cool water and use a wetting solution before inserting a lens, because it may irritate the eye. I find that the cleaning solutions that have a gellike consistency tend to do a slightly better job than the more liquid ones; perhaps this is because they require more rubbing, an essential factor in mechanical cleaning.

Soaking Solution. In addition to further removing the oil and protein deposits, a soaking solution is a disinfectant. It protects the eye from bacterial and fungous infections. Soaking solutions also keep your lenses moist; though essentially hydrophobic, PMMA does absorb a slight amount of water. Tap water is not a suitable substitute, since the minerals it contains irritate the mucous membranes in the eye. It may also cause insoluble calcium deposits to form on the lenses, and it isn’t sterile. Make certain that you change the soaking solution each day and clean the storage case with hot water once a day.

Some practitioners prefer to store the lenses in a dry state. No microorganisms except for fungus spores can survive under dry conditions.

Although both these procedures are acceptable, I prefer the soaking method and feel that the lenses are cleaner and more comfortable when kept moist continuously.

All-in-One Solutions. A few companies produce an all-purpose solution to be used for wetting, cleaning, and soaking. Although this may be a convenience, I prefer the use of separate solutions because each contains different ingredients for its specific function. Anything else represents a compromise, because the various ingredients would negate each other’s effectiveness. For instance, substances that are contained in good soaking solutions negate the wetting effect; also the cleaner in a cleansing solution would be an irritant when it came into contact with the eye.

Comfort and Lubricating Solutions. These are instilled into the eye while the contact lenses are in place. They rewet, lubricate, clean, and cushion the lenses, and act as a kind of “artificial tears” that aid the spread of the normal tears. They are particularly useful for “dry eyes” that result from hormonal disturbances (such as the dryness of the mucous membranes that occurs after menopause, allergies, antihistamines, and birth control pills). They may be used as often as needed. Although the lubricating solutions are essentially the same, some patients may prefer one to another. These solutions are specially formulated to be used with contact lenses, and should not be confused with ocular decongestants, which whiten the eye and are not recommended.

Fenestrations are especially useful when the lens has to remain relatively large because of fitting or optical factors. They make better use of the available tears for hard-lens wearers who have a “dry eye syndrome,” for inadequate blinkers, or for those wearing lenses in low humidity. There are also contacts with edged grooves or “vents” that are meant to serve the same purpose as fenestrations.

Some doctors prescribe and fit fenestrated or vented lenses routinely, especially in patients who are over thirty or who have dry eyes. They report a shortened adaptation period (with some patients wearing their contacts for eight hours the first day); decreased likelihood of overwear syndrome; and little or no spectacle blur or photophobia (light sensitivity). Others add fenestrations after normal wear has proven unsatisfactory; it’s been estimated that about 20 percent of conventional hard-lens wearers will eventually need at least one fenestration. Others, however, report no greater comfort.

I have found that many patients complain of an unacceptable amount of visual distortion because of the fenestrations, or discomfort because the holes interrupt the smooth surface of the lens. Moreover, when the holes become clogged with mucus and debris, it becomes almost impossible to wear the lenses. Therefore I rarely prescribe fenestrated or vented lenses until all other possible avenues have been explored.

WETTABILITY

Another development making conventional hard contact lenses more comfortable involves reducing the wetting angle, which relates to the ease with which tears are able to spread over the surface of a contact lens. All surfaces vary in their “wettability”: on a highly polished or waxed surface, water beads up into little balls and the angle between the surface and the droplet is very steep or high. Such a surface has a high wetting angle.

On the other hand, on a surface that’s not waxed or polished or that’s been washed with detergent, water won’t form little round beads; instead it tends to flatten out and keep a low profile. The angle between the surface and the resultant puddle is very low or flat, and the surface has a low wetting angle.

This wettability property applies to the plastics in contact lenses. Depending on surface conditions, these plastics can vary in wetting angles. The lower the wetting angle, the easier it is for tears to spread under the lens, thus bringing more oxygen to the cornea. Wettable lenses are also more comfortable; putting a dry lens on your cornea is an irritating experience you’ll not soon forget. Wetting the plastic lens therefore makes it easier and safer to wear. Wetting solutions were invented because water and tears will not spread adequately over an untreated, dry PMMA lens. Unfortunately the wetting solution traditionally used with hard lenses works for only about an hour. Longer-lasting methods now exist: Some lenses are more wettable because they’re made of a modified PMMA; others have a lower wetting angle by virtue of a special permanent coating, and still others require constant instillation of lubricating eye drops to keep them comfortable.

• Must have the sharpest visual acuity possible.
• Have a high amount of astigmatism.
• Have moderately “dry eyes.”
• Are concerned about the cost.
• Use topical eye medications.
• Prefer an easy lens care system.
• Desire a durable lens.

NEW DEVELOPMENTS IN COMFORT

One of the reasons for rigid-lens failures is due to the fact that PMMA allows neither oxygen-rich air nor oxygen-rich tears to pass through it. Your cornea needs oxygen to remain healthy; in hard lenses it relies mainly on the tears that flow under the lens and are replenished with each blink. If the tears‘ supply of oxygen isn’t sufficient, the lens is uncomfortable and can’t be worn for very long. (Gas-permeable contact lenses, which are not made of PMMA, are a big threat to the future of conventional hard contact lenses because they retain most of the hard lens’s advantages and few of their disadvantages. Another cause of discomfort in hard lens wear is the constant rubbing of the upper lid as it crosses the inflexible lens edge during each blink. Standard lenses are being made more comfortable in several ways to overcome these discomforts.

SIZE AND THICKNESS

The modern conventional rigid lens is usually between 8 and 10 mm in diameter and doesn’t cover the cornea completely. Earlier hard lenses were much larger and covered not only the cornea, but the sclera (white part of the eye) as well. Over the decades improved fitting and manufacturing techniques have allowed the lenses to gradually shrink in diameter and thickness. Now we even have “ultra-thin mini-lenses” with a center thickness of .035 mm and less than 8 mm in diameter. These contacts are very comfortable for a hard lens but difficult to fit, since they have to be centered perfectly over the pupil. Unlike the larger lenses, which have a large tolerance of movement without adversely affecting vision, these small thin lenses should move only slightly with each blink; otherwise blurred vision will occur. If a cornea is too steep or too flat or has too much astigmatism, the mini-lens should not be prescribed. For people who can wear them, however, small, thin lenses are more comfortable for several reasons. Well-fitted ones are more likely to float on a layer of tears and less likely to touch the cornea, so there’s less sensation. They also touch the lids less, further increasing comfort. In addition, small lenses that are thin enough to flex during the blink help tear circulation, thereby reducing the possibility of overwear syndrome. (The larger the lens, the greater the distance tears have to travel once they’ve entered under the lens edge. By the time they reach the center of the cornea, much of the oxygen has been depleted.) Contacts must, however, remain large enough to cover a fully dilated pupil so that night vision isn’t adversely affected. Thin mini-lenses must also be handled more carefully to avoid loss and warpage.

Each advantage and disadvantage of the various types of contact lenses must be weighed and evaluated according to each individual case. There are still more rigid-lens wearers than soft-lens wearers, possibly because hard lenses have simply been around longer, and because lower cost, easier upkeep, and better vision override soft lenses‘ main advantage: comfort. On the other hand newcomers to the contact lens scene more often seem to prefer the comfort and ease of adaptation found in soft lenses. There’s a contact lens created to suit just about every need. Your eye doctor is best qualified to determine which lenses will best correct your visual deficiencies and still provide comfort and safety.

Remember that the ability to wear a certain type of lens (or any contact lens at all) depends to a large degree upon the chemical makeup, amount, and behavior of the tears. Tears lubricate, cleanse, and supply the eye with nutrients. If you have too much mucus, or protein, or lipids, these deposits can cling tenaciously to the lens surface and are especially hard to remove from soft lenses. A deficiency in any component can render the eyes too “dry” for successful contact lens wear, even if the watery layer is sufficient. That’s why you may be able to wear soft lenses without a hitch, but your best friend can’t. Then, too, some eyes need a greater amount of oxygen than others and some eyes fail to adapt to the lower metabolism imposed upon the eye by any contact lens. These complications often only become evident after the lenses have been worn for some time, and may take patience and a good deal of skill and expertise on the part of the eye practitioner to overcome.

Hard and Soft Lenses Compared

Hard Lenses

• Uncomfortable at first; may need 1 to 2 months to adapt to all-day wear (average 8 hours).
• Easy care; inexpensive to keep clean; disinfection unnecessary.
• Durable, long life—some up to 10 years.
• Excellent visual acuity; consistently clear, sharp image for all refractive errors.
• Lenses must be removed and cleaned when dirt or dust gets between them and cornea.
• Vision may be temporarily blurry after removal (”spectacle blur”).
• Once adapted, should be worn same number of hours each day.
• Eyelid sensation with each blink.
• Tend to pop out or move off center.

Soft Lenses

• Comfortable almost immediately; adaptation to all-day wear is only about 1 week.
• Cleaning more involved and slightly more expensive; disinfection necessary.
• More delicate, less durable—most need replacement after 2 years.
• Less satisfactory correction, especially in astigmatism.
• Dust and dirt rarely get under lenses.
• No spectacle blur.
• Can wear intermittently for special reasons (evening, sports, etc.).
• No eyelid discomfort.
• Less chance of popping out or moving around eye—best for sports.

HARD Lenses

• Relatively low in cost.
• Prescription of lens can be reground to accommodate slightvisual changes.
• Danger of overwearing and corneal damage.
• Some side glare and reflections from edge of lens; increased sensitivity to light.
• Average daily wearing time: 8 hours.
• Unaffected by atmospheric conditions; doesn’t absorb foreign substances.
• Routinely tinted. May put dot on right lens.
• Difficult to wear with dry eyes.
• Scratches on lenses may be polished.

SOFT Lenses

• Higher cost.
• Vision change requires new lens.
• Less danger of injury from overwearing.
• Little side glare—better for night driving; little or no increased light sensitivity.
• Average daily wearing time: 14 hours.
• Can be uncomfortable in dry air; can absorb and accumulate substances such as hair spray, chemical fumes, even eye secretions.
• Tinting is possible, but not yet routine nor widely available.
• Almost impossible to wear with dry eyes.
• Scratched lens has to be discarded.

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.