Contact lens update
More and more people find contact lenses an appealing, convenient, unobtrusive and infinitely preferable alternative to spectacles. Contact lenses have several advantages over ordinary eyeglasses. They give excellent vision (especially for those who are myopic or short-sighted), reduce peripheral distortion, are comfortable and convenient, don’t steam up, fall off or break during athletics, facilitate use of optical instruments (such as telescopes, binoculars or microscopes) and are considered more flattering.
However, not everyone can wear contact lenses. People with dry or sensitive eyes often find them irritating and scratchy, and may develop bloodshot eyes (although they may tolerate contacts for “special occasions”). People whose contacts repidly build up deposits might also find them annoying.
Extra time and effort required for contact lenses
All contact lenses require more care and attention than ordinary glasses because they tend to get coated with protein deposits and, since they touch the eyes, can easily transfer dirt, debris or bacteria onto them. They must be kept scrupulously clean with recommended disinfectant fluids to avoid contamination. At the very least, contact wearers must stock up on the necessary solutions and be sure to wash the hands before putting in or removing the lenses. And contact lens wearers need a backup pair of regular, up-to-date prescription eyeglasses to wear in case of eye infection or fatigue, or when suffering from a severe cold (because of secondary eye infection), and to give the eyes an occasional “rest” from contacts.
Sorting out the different contact lenses
Contact lenses are thin plastic (occasionally silicone) discs, made to prescription, that float on top of the tear layer that covers the cornea — the eye’s transparent outer covering. The watery layer of oil and tears holds them tightly in place. Good contact lenses allow the cornea to breathe (get oxygen) by gas exchange under the lens.
There are two main types of contact lenses: soft and rigid, both available in several forms.
Rigid, gas-permeable forms are especially good for those with astigmatism, and, given proper care, can last for years. But in contrast to soft contacts, which may feel comfortable almost at once, it can take several weeks to get accustomed to rigid lenses, and wearers generally remain aware of their presence.
Soft contact lenses are now the most popular form, cornering 80 per cent of today’s contact lens market. Easier to adapt to than rigid lenses, they are made of water-rich, flexible plastic that promotes oxygen flow. Comfortable to wear, and usually non-irritating from day one, soft contacts are less likely to be dislodged when playing sports. They can be crafted to correct for astigmatism but are then harder to fit. Soft lenses are less durable than rigid types and rip easily.
Bifocal contact lenses are available in both rigid and soft forms, but are time-consuming to fit.
Tinted contact lenses are easier to see when handling, and can also change eye colour to the desired hue — perhaps from brown to blue or purple, or from a light to a darker shade.
“Daily wear” contacts now most recommended
Most eyecare specialists today recommend “daily wear” contact lenses removed at night. Daily wear contacts can be kept for months to years if well cared for. But nowadays, many opt for frequent-replacement (disposable) soft lenses that are worn for a few weeks, then replaced by a new set.
Extended-wear contact lenses, left in overnight and even for a few days before removal for cleaning, are now strongly discouraged because of health risks to the eye, such as corneal ulcers. Wearing contacts with eyes closed diminishes the eye’s oxygen supply and, together with the tendency to collect deposits (which further reduces oxygen absorption), increases the threat of eye damage. (Studies show a tenfold increase in corneal ulceration with extended wear soft contact lenses.)
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“Frequently replaced” or disposable daily-wear soft contact lenses are rapidly becoming the favourite type. Many consider them the “healthiest way to wear contacts,” with the least hassle. Thin and very comfortable, they are worn for two to four weeks, then discarded and replaced by a fresh set. They are particularly suitable for wearers whose contacts rapidly accumulate deposits or frequently rip. The advantages of disposables are: convenience, comfort, good oxygen transmission, simple care, no need for elaborate cleaning routines and “spares always on hand.” Disposables require no special cleaning other than overnight disinfectant soaks and storage in disinfectant fluid when not worn. “However,” warns one optometrist, “they should not be kept in overnight as wearing them with eyes closed can cause swelling and damage the cornea.” (The newest disposable types are worn for one day only, then trashed, but they are very expensive.)
Since contact lens wear increases infection risks, wearers need to keep an eye out for, and stop wearing them at, the slightest hint of eye irritation or infection: “When in doubt, take them out.” The eye’s diminished oxygen supply with contact lens wear and the frequent handling easily allows bacteria to enter the eye, can scratch the cornea, leading to keratitis (inflammation of the cornea) or corneal ulcers (little holes that allow in infective organisms). Eye infections typically cause redness, pain, sticky secretions, blurry vision and light-sensitivity. If not swiftly treated, the infection can scar the cornea, decrease vision and even necessitate a corneal transplant. Most infections are due to bacteria (such as staphylococcus), but there’s even greater concern about (rare) fungal or amoebic infections that are hard to eradicate.
Latest contacts have inbuilt ultraviolet (UV) protection
Soft contact lenses that incorporate a UV-absorbent material (already widely used in Europe), have just hit the Canadian market, offering UV-protection added to the convenience of disposables. The new UV-blocking lenses, approved by Canada’s Health Protection Branch, contain a material that absorbs ultraviolet radiation without reducing brightness. Once absorbed, the UV radiation is neutralized, converted into heat and then transferred into the air. The annual cost is only slightly more than for ordinary disposables. Exposure to UV radiation increases risks of cataracts, photokeratitis (“sunburn” of the cornea or “snow blindness”) and retinal damage. As depletion of the ozone layer threatens human eyes, we should all protect them from ultraviolet rays.
Contact wearers still need sunglasses to cut glare
Even UV-absorbent contact lenses do not replace sunglasses, still needed to cut brightness and glare. Ordinary sunglasses do not block ultraviolet radiation unless they have a coating that absorbs light in the 286 to 400 nm range. Some sunglasses have a little UV-filtering ability, but effective ones (which are usually amber or brown, rather than purple or gray) cut at least 90 per cent of UV radiation. General-purpose dark glasses — suitable for activities such as driving, tennis, hiking or skating — should screen out 95 per cent of UVB (short-wave UV rays) and 60 per cent of UVA (longer-wave UV radiation). For brighter situations such as skiing, boating and sunny beaches, better UV-blockage is advised (which cuts 99 per cent of UVB and at least 70 per cent of UVA). Check the labels on sunglasses for the UV-blocking capacity to see whether they’re marked “400 nm and below” or something similar. If not, ask the manufacturer how much UV-blockage they provide. Never wear dark glasses at night as they compromise vision. Make sure all eyeglasses, dark or clear, are impact-resistant.
Tips for contact lens care and wear
* Be sure the contact lenses fit well (after a thorough eye exam).
* Comply with lens-care instructions: do not become careless or complacent about your eyes!
* Always wash, rinse and pat hands dry before handling lenses.
* Discard lenses after the prescribed wearing time, and also discard over-aged, dirty or damaged contact lenses.
* Do not wear contacts overnight (when asleep or taking naps) unless recommended by your eye-care practitioner.
* Ask about the advisability of wearing contacts when swimming or doing other water activities.
* Do not use saliva to wet your lenses.
* Eyedrops should not be used while wearing contact lenses unless recommended by an eye-care specialist.
* Use only recommended solutions for lubricating, wetting or storing your lenses. Avoid nonsterile homemade saline solutions — their use has caused serious infections. Never store contacts in water.
* Always use fresh solution in your lens case to disinfect contacts. Never re-use or “top up” contact solution.
* Keep the cases clean! Empty out used solution and air-dry cases after removing lenses. Get new lens cases periodically (to prevent bacterial build-up).
* Do not store bottles of contact solution for long periods. Discard and get a new one, even if there’s some solution left.
* Watch for warning signs of eye trouble. Remove contacts immediately if the eyes become red, weepy, painful or if vision worsens while wearing them, and consult an eye-care practitioner.
* Avoid getting lotions, creams or sprays on your contacts. Put in lenses before applying make-up and remove before taking it off. Don’t use old eye make-up, or share eye make-up. Water-based cosmetics are least likely to damage lenses.
* Be sure to have eye examinations every 6-12 months or as recommended by your eye-care practitioner. Schedule and keep follow-up appointments.
COPYRIGHT 1994 Strategic Inc. Communications Ltd.
COPYRIGHT 2004 Gale Group
