Contact lenses are a popular choice for many people who require vision correction, because they afford flexibility and convenience. Different lenses are available to treat myopia (nearsightedness), hyperopia (farsightedness), astigmatism (blurred vision due to the shape of the cornea), and presbyopia (inability to see close up). The US Food and Drug Administration (FDA) not only regulates contact lenses as medical devices but also wants to ensure that people use them safely and effectively, because they are used by people without professional medical assistance. Medscape interviewed Bernard P. Lepri, OD, MS, MEd, optometrist and clinical review scientist in the Office of Device Evaluation at the FDA, about the issues regarding safe use of contact lenses and the important information clinicians need to know about the risks involved.
Contact Lens Types and Materials
Medscape: Can you describe the different types of conventional contact lenses available, including their material and composition?
Dr. Lepri: There are 2 types of contact lenses that are categorized by material and composition: soft contact lenses, which are the most popular, and rigid gas-permeable contact lenses. Within the category of soft contact lenses are 2 material subcategories: conventional hydrogel and silicone hydrogel. The silicone hydrogel lenses actually have 5 different material subgroups underneath them, so you can see how complicated the technology of contact lenses has become over the years.
Contact lenses are also categorized by their usage patterns, and there are 2 categories: daily wear and extended or overnight continuous wear. Extended-wear lenses can be either soft or rigid gas permeable, although the percentage of extended-wear rigid gas-permeable lenses is extremely low. The limits of extended wear can range from 6 to 30 nights of wear, depending on the lens material and what the approval was through the FDA.
Many different lenses are available for a variety of needs and preferences. Contact lenses can be used to correct vision disorders, such as myopia, hyperopia, astigmatism, and manage presbyopia, for whom those of us who are over 40 years old are all too familiar with.
Medscape: Can you describe contact lenses that are available for specialized use (eg, orthokeratology and decorative lenses)?
Dr. Lepri: Orthokeratology, traditionally known as "Ortho-K," is a lens-fitting procedure that uses specially designed rigid gas-permeable contact lenses to change the curvature of the cornea so that you temporarily improve the eye's ability to focus on objects. This procedure is primarily used for the correction of myopia. Overnight Ortho-K lenses are the most common type, but some are prescribed only for daytime wear. Overnight Ortho-K lenses are commonly prescribed to be worn while sleeping for at least 8 hours each night, and they are removed upon awakening; you do not wear them during the day.
Some people can go all day without their glasses or contact lenses, and others will find that their vision correction will wear off during the day. The vision correction effect with orthokeratology is temporary. It is not a permanent change. If Ortho-K is discontinued, the cornea will return to its original curvature and the eye to its original degree of nearsightedness. Ortho-K lenses must be worn every night, or on some other prescribed maintenance schedule as determined by an eye care professional, to maintain the treatment effect.
The FDA requires that eye care professionals be trained and certified before fitting overnight Ortho-K lenses. Patients should always ask what lenses their eye care professional is certified to fit if they are considering this procedure.
Decorative lenses just change the look of the eyes. They can temporarily change your brown eyes to blue, or make your eyes look like cat eyes or vampire eyes for Halloween. They do not correct your vision, although there are those available that can correct your vision and be decorative as well. Decorative contact lenses are also called "fashion contact lenses," "Halloween contacts," "colored contact lenses," "cosmetic contact lenses," or "theater contact lenses," to name a few. There are numerous types that are out there.
Because there are many illegally marketed lenses that have not been FDA cleared for daily wear, many teenagers who have never worn or been examined and fit for contact lenses obtain them from nonmedical sources, such as street vendors, beauty supply stores, flea markets, novelty stores, or the Internet. Wearing any kind of contact lenses, including decorative ones, can cause serious damage to your eyes if the lenses are not used correctly.
Decorative lenses have been a news topic over the past couple of years because of serious sight-threatening complications, which in some cases resulted in corneal transplant surgery. The take-away message is that contact lenses should only be purchased from a licensed eye care provider who has performed a thorough eye examination and a contact lens fitting examination.