Contact lenses are small plastic disks, shaped to correct a refractive error such as nearsightedness, farsightedness, astigmatism, and presbyopia. Contact lenses are placed directly on the eye, where they float on a film of tears in front of the cornea. Correct design and fitting of the contact lenses are essential for comfort, safety, and accurate correction.
Improvements in contact lenses have made them more comfortable and easier to wear. For many people, contact lenses offer a relatively safe and effective way of correcting vision problems.
Types of Contact Lenses
Several types of contact lenses are available to correct nearsightedness and other refractive errors.
Rigid (hard) lenses
- Rigid gas-permeable (RGP) lenses
- Conventional hard (PMMA) lenses (polymethyl methacrylate, or PMMA)
Soft (hydrophilic or hydrogel) lenses
Soft (hydrophilic or hydrogel) lenses are made of soft, very flexible plastics that absorb water (up to 90% of the lens weight). Many people find them more comfortable to wear than hard lenses, but hard lenses may provide sharper vision. Soft lenses are also more fragile than hard lenses and require more intensive cleaning. Types of soft lenses include:
Adaptation of Contact Lenses
With most types of contacts, there will be a 2 to 4 week break-in period during which you will wear the lenses for increasingly longer periods of time each day.
Why Wear Contact Lenses?
Most people choose to wear contacts because of the convenience and because people prefer the way they look without eyeglasses. Contact lenses may also be used to treat eye diseases, such as keratoconus, and corneal scars caused by injury or infection.
Contact lenses can correct nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and combined refractive errors. Lenses that correct astigmatism are called toric lenses. They may need to be custom-made and may be more expensive than ordinary contact lenses.
Who Is Suitable For Contact Lenses?
People who are generally well-suited to wearing contact lenses (hard or soft) include those who have:
- Moderate to high refractive errors (people who have significant trouble seeing things at a distance and need vision correction all the time).
- People who wear eyeglasses only part of the time are less likely to wear contact lenses successfully.
- Strong motivation. You have to be willing to tolerate minor discomfort during the break-in period, and to learn and use proper methods of storing and handling your contact lenses, including maintaining good hygiene.
- Contact lenses are preferred over glasses for people who perform work, or play sports in which glasses are inconvenient or dangerous.
Factors Affecting Successful Contact Lens Wear
The following factors may mean that contact lenses are not a good choice for you:
- You would be unable or are not willing to care for the contact lenses properly.
- You would have a hard time handling the contact lenses (for example, if you have severe arthritis in your hands or another problem that would make it hard for you to insert, remove, and clean the lenses).
- You have certain medical conditions such as diabetes or hyperthyroidism. Allergies, asthma, hay fever, and other chronic respiratory disorders may make it difficult to wear contact lenses.
- You have dry eyes or problems with the cornea. People who have Sjögren’s Syndrome (a condition that causes a lack of tears and dry eyes) are often unable to wear contacts. People who have chronic or recurrent infections or sores on their cornea can not wear contact lenses.
- You have a job that exposes you to chemical fumes or other vapors that may be absorbed by or stick to the contact lenses (such as paint, spray chemicals, or hair spray).
- Infants and children usually do not wear contact lenses, except to treat some medical conditions. Many teenagers wear contacts, but parents must accept the need for frequent changes in the prescription until their eyes stop changing in the late teens or early 20s.
What To Think About…
After going through the time and expense of fitting contact lenses, some people find they are unable to wear them. Allergies, dry eyes, discomfort during the adaptation period, the “hassle factor,” and discomfort are frequent causes of a person’s inability to wear contacts.
It may take time to find the type of contact lens and the wearing schedule that is best for you. There are a wide variety of contact lenses available. Look for an eye care professional who is willing to work with you to select the best type of lens for your needs and your lifestyle.
The care of contact lenses varies according to the type of lens. Care may range from minimal (disposable extended-wear soft lenses) to extensive (conventional soft lenses). It is important to follow directions for lens care carefully to avoid vision-threatening complications. If you have a hard time following the cleaning steps, tell your eye care professional. There may be ways to simplify the cleaning steps, or you may want to switch to disposable lenses.
Many people have problems with their contacts because they do not follow instructions on wearing time, disinfection, and other cleaning and care practices. For best results and to protect your eye health, follow these instructions closely.