Soft Toric Contact Lenses
What are soft contact lenses?
Contact lenses (contacts) are corrective lenses that are worn directly on the eye. Soft contacts are made from a plastic called hydrogel and are about 35‰ to 80‰ water. Water makes the lenses flexible, comfortable and allows for oxygen permeability.
Contact lenses rest on the cornea. The function of the cornea is to focus light onto the retina. The cornea does not have blood vessels so it gets oxygen directly from the air. Since soft contact lenses cover the entire cornea an adequate amount of oxygen must pass through the contact to maintain the health of the eye.
Only an optometrist or ophthalmologist should fit soft contact lenses. To determine if contact lenses are an option for a patient, the eye doctor will perform a complete eye exam and measure the curvature of the cornea. The eye doctor may need to use trial lenses of several different brands, materials, powers and sizes before finding the best lens for each patient. An eye care professional will demonstrate proper insertion, removal, and disinfection of the contact lenses.
Patients who wear contact lenses should be examined at least one time each year. The doctor will examine the health of the cornea and update the patient's prescription. The eye doctor will also identify and correct any problems that may be caused by contact lens wear.
What do soft contact lenses correct?
Soft contact lenses are used to correct a variety of visual disorders including:
- myopia (nearsightedness)
- hyperopia (farsightedness)
- astigmatism (uneven curvature of the cornea)
- presbyopia (age-related decrease in near vision)
Many patients prefer contacts to glasses for cosmetic reasons or during exercise. Contacts also have less image distortion and greater field of view than glasses. Specialty soft contact lenses can be used to change eye color or to improve the appearance of an abnormal eye. Eye doctors may also use a soft contact lens as a temporary "bandage" to relieve eye pain from a corneal injury or surgery.
Who cannot wear contacts?
Although most patients can successfully wear soft contact lenses, they may not be appropriate for everyone. Patients that have frequent eye infections, dry eye syndrome, ocular allergies, or certain other eye conditions may not be able to successfully wear contacts. Contacts are also not appropriate for patients who are exposed to dust and chemicals or who cannot properly handle the lenses.
What are Disposable Soft Lenses?
Today, most soft contact lenses are disposable and must be replaced at certain intervals depending on the manufacturer's and your eye doctor's recommendation. The most common replacement schedule is every two weeks, but there are also lenses that are replaced every day, month, or 3 months. Non-disposable or "conventional' lenses are less common and must be replaced every year. Non-disposable lenses may be the only option for very high or unusual prescriptions. Frequent lens replacement helps ensure that contaminants such as bacteria, mold and fungus will not form on the contacts.
Although most lenses need to be removed at night, extended wear silicone-hydrogel lenses were approved for overnight wear by the FDA in 1999. These lenses may be worn continuously for up to 30 days and then replaced. Eye doctors may modify the wearing schedule of extended wear contact lenses to the patients' needs. Even though silicone-hydrogel lenses transmit up to 6 times more oxygen to the eye than traditional contacts, eye infections and inflammation are still possible when wearing these lenses overnight.
How Do I Clean and Disinfect Soft Contact Lenses?
Naturally occurring mucous, protein and lipids can accumulate on the lenses in the form of deposits, which can irritate the eyes and can also act as a depot for bacteria. Proper cleaning and disinfecting keeps the lenses free of deposits and bacteria.
There are two main types of lens care products, multi-purpose solution and hydrogen peroxide solution:
- Multi-purpose Solutions have a disinfectant and cleaner conveniently combined in one bottle. The solution is strong enough to kill the most common contact lens contaminants, but not so strong that it irritates the eye. Although multi-purpose solutions advertise that they do not require the wearer to rub the contacts, they do recommend rinsing each side of the contact with the solution for 5 seconds before storing the lenses in their case. Many eye doctors recommend rubbing the contacts because it is more effective and wastes less solution than rinsing. The wearer should put an ample amount of solution in the palm of one hand and gently rub the lens for about 10 seconds with the index finger of the other hand.
- Hydrogen Peroxide Solutions work differently than multi-purpose solutions. In this method, the lenses are disinfected and cleaned with 3‰ hydrogen peroxide. The lenses are stored in a special vial that is designed to neutralize the hydrogen peroxide. It is important to leave the contact lenses in the vial until the hydrogen peroxide has been neutralized. Inserting the contact lenses before the solution is neutralized can cause chemical burns to the eye. The lenses should not be rinsed with the hydrogen peroxide solution prior to insertion. The vials become less effective at neutralizing over time and need to be replaced with each purchase of solution. This method is a good alternative for patients who are sensitive to multi-purpose solutions because after the hydrogen peroxide is neutralized, it is free of disinfectants, preservatives and cleaners.
Advantages & Disadvantages
The advantages of a soft toric contact lens include easy adaptability, as comfort is usually quite good even initially. Other advantages of soft toric lenses include:
- Extended wear option –allowing up to thirty days of continuous (overnight) wear
- Eye color –soft torics are available in various colors that can change even the darkest eyes to a variety of colors
- Convenient replacement schedules –conventional lenses allow you keep the same lenses for a year, or the more common "disposable lenses' allow you to wear for one month, 2 weeks, or only once and throw away, with no need to ever clean them
Their biggest disadvantage is the potential for fluctuating vision. No matter how good the lens design and fit, all soft toric lenses rotate and move a bit in the eye. As explained earlier, this can be a source of frustration when you can see clearly one minute, and are blurry the next. The more astigmatism a person has, the more likely he/she will be sensitive to the lens movemen
