Contact Lenses

Types of Contact Lenses

Contact lenses are tiny, curved plastic discs which are microthin, very light and barely visible. There are two major types: hard and soft. Hard Lenses

 

The hard lens covers about two-thirds of the cornea and may be clear or tinted. This lens has been improved so that it can be made into a bifocal, toric or bitoric lens. The hard, gas-permeable lens resembles the hard contact lens but is made of a material that allows oxygen to cross through the lens to the cornea, which is healthier for the cornea. Today, virtually all hard lenses are made in gas permeable plastics. The scleral contact lens covers the whole front of the eye and is still used for certain medical conditions. The latest version of this lens design is used in the management of advanced Keratoconus. The X-chrome lens is a hard, red contact lens which, when fitted on the non-dominant eye, allows people who have a particular kind of “color blindness” (those who can’t discriminate between red and green) to partially distinguish colors. It is worn in only one eye (the weaker, “non-dominant” eye) and may be made with a prescription for patients who would also need eyeglasses to correct for vision.   Soft Lenses

The soft, or hydrophilic, lens is made of a special thin and very flexible plastic which absorbs water. It is larger than the hard lens and covers all of the cornea and extends to the sclera. Soft astigmatic bifocal and colored lenses are available. Daily-wear lenses were the first type of soft lenses available. These lenses are approved to be worn and removed on a daily basis. Patients may not sleep or nap with these lenses and are expected to clean and disinfect them whenever handled. A wide variety of soft daily-wear lenses are currently available on the market, including colored, bifocal and toric.

Extended wear lenses have been approved for patients after cataract surgery and for patients with myopia, hyperopia and astigmatism. These are soft lenses that allow better oxygen transmission to the cornea and need not be removed on a daily basis. They provide the visual benefits of contact lens wearing for many patients who cannot or do not wish to handle daily wear lenses. Because of the nature of these lenses, more frequent return visits are necessary. Extended-wear, hard, gas-permeable lenses are also available. The disposable contact lens is one of the latest soft lenses available and may be worn as extended wear, daily wear or single-use lenses. As extended wear lenses, they are designed to be worn for one week and then thrown away. They are replaced with a new pair. No maintenance is required in caring for the lenses, but because they are dispensed in three-month or six-month supplies, wearers must follow a strict schedule of checkups to be re-supplied with lenses. Extended-wear lenses are available for myopic (nearsighted) and hyperopic (farsighted) patients. As daily-wear lenses, these are designed to be worn for one to two weeks. A specific schedule will be determined by the doctor. When removed daily, they must be soaked in disinfecting solution overnight. They are available for myopic and hyperopic patients.

Single-use lenses are designed to be worn for one day and then thrown away. These lenses are currently available only in limited prescriptions. The latest innovation in soft lenses is the Silicone gel lens. These lens have a silicone backbone and are much more biocompatible than traditional soft lens. These lenses are used for extended wear, dry eyes and eyes that need more oxygen. Aphakia

Aphakia is a condition resulting from cataract removal. Aphakic contact lenses replace the heavy, thick glasses used after cataract removal and provide superior vision. Today aphakic lenses are used when an intraocular lens (IOL) implant is not inserted in the eye at the time of cataract removal. This is usually the case with infants and small children that need cataract surgery. When a patient is aphakic in one eye and has a normal lens in the other, clear eyesight with both eyes can only be achieved by wearing a contact lens in the operated eye. Eye Trauma

Contact lenses may be necessary to restore vision after an eye injury, particularly in children and young adults. Keratoconus

Keratoconus is a disease which causes the cornea to protrude and become progressively thinner and cone-shaped. Eyeglasses usually cannot fully correct this condition, and in advanced cases, patients can only obtain useful vision with specially designed hard lenses. Very severe cases that cannot be fit with lenses or cannot get useful vision with contact lenses may require a corneal transplant. Contact Lens Fitting Procedure

Before contact lenses can be prescribed, a complete eye examination is required. No contact lens should be fitted without a thorough eye exam as a first step. The type of lens best suited for you should be the subject of a discussion between you and your doctor. Your eye doctor will determine the strength of the lenses, and inspect your eyes and lids for possible allergies or infections. The curvature of the eye must be measured and other special tests may have to be performed. Contact lenses, both hard and soft, are held in place by adhering to the film of tears that normally covers the front of your eye. A membrane that lines the front half of the eyeball and lines the underside of the eyelid makes it impossible for the contact lens to go behind the eye or to wander anywhere but under the lid. After you are fitted, there may eye discomfort, but there should be no pain. As you become accustomed to the lenses, wearing time should increase and discomfort decrease until maximum wearing time is finally reached. This may take three to four days for soft lenses, and two to four weeks for hard lenses. Some symptoms experienced during the adaptation period are tearing, blinking, sensitivity to light, head tilt, and a slight redness of the eye. All of these symptoms are temporary and should disappear by the end of the third week. If not, notify your eye doctor. Patients should be alert to any signs of infection, corneal abrasion and swelling. A small percentage of patients have a great degree of sensitivity and never quite adapt to contact lenses. They are usually told that they are not ideal candidates and should not be wearing contacts. Lens Care Guidelines

-If you live in a polluted area, your lenses may need to be cleaned more frequently Soft Lenses

-In addition to the daily cleaning, soft lenses require a weekly enzymatic cleaning to remove protein deposits and to ensure clean, healthy lenses  

When Should Contacts Not Be Worn

Wearing contacts while sleeping can cause eye irritation, discomfort and, sometimes, corneal disorders. Only extended-wear lenses can be worn full time. As a rule, lenses should not be worn while swimming, or sitting in a hot tub. Under special circumstances and only with a eye doctor’s permission, some patients may be able to wear their lenses while swimming, if they wear good protective goggles.  

Contact Lens Warning Signs

Because vision is sharper with contact lenses than with eyeglasses, you may notice that you do not see as clearly when you first put on your glasses after removing your lenses. This should only be a temporary sensation, and you should become oriented to your glasses in a minute or two. However, if there is blurriness or an actual change in the clarity of your vision, and if it is more than momentary, you should consult your physician immediately. A small percentage of soft contact lens wearers may be at risk of development of vision-threatening corneal ulcer or ocular infections. However, by adhering strictly to your eye doctor’s recommended lens care guidelines, chances are excellent that these complications can be prevented. Acute pain and redness are symptoms which require immediate removal of the lens and prompt attention by an ophthalmologist. Early detection of complications is essential to successful treatment. Call your doctor if:

-Your adaptation period is up and you have unusual light sensitivity, see rainbows or halos around lights or have blurred vision  

Advice for Contact Lens Wearers

-Do wash, rinse and dry your hands before handling the lenses –Do carry identification stating that you wear contacts, so they can be removed in case of an accident -Do follow your doctor’s instructions about regular checkups -Do learn to insert and remove lenses correctly -Do keep a backup pair of glasses -Do be careful applying makeup; apply after insertion of the lenses -Do carry your contact lens case and glasses at all times -Do use only those solutions recommended by your doctor -Do use commercially prepared saline and other cleaning solutions -Don’t rub eyes while wearing lenses -Don’t wear damaged lenses -Don’t wear lenses while sleeping, or continuously, unless specifically prescribed by your doctor- Don’t use any eyedrops on your lenses without your doctor’s approval -Don’t insert, remove or work with lenses over a wash basin -Don’t place lenses on top of anything warm; they will melt -Don’t wear lenses while under a hair dryer or around harsh fumes -Don’t use saliva or tap water on your lenses as a wetting agent -Don’t use homemade saline solution or distilled water in preparing your lens care products -Don’t reinsert your lenses without disinfecting them  

Frequently Asked Questions

Should I wear contact lenses? Many people who wear contacts instead of glasses are happier because they feel they look better. The most important key to successful contact lens wearing is strong personal motivation! Are you willing to put up with certain discomforts? To learn the proper techniques of cleaning and taking care of the lenses? To keep to your wearing schedule? To have regular checkups? If you can answer YES to the above, you probably have the attitude and motivation to wear contact lenses successfully.   Which contact lens is best for me? Hard, Gas-Permeable Lenses Advantages:

-Do not absorb chemicals, impurities and pathogens Disadvantages:

-Do not last as long Extended-Wear Lenses Advantages:

-More frequent followup appointments are required