Vision Problems

Corrective Eyewear
by Food and Drug Administration (FDA)

(Page 2 of 5)

The NEI estimates that more than 150 million Americans spend over $15 billion each year on corrective eyewear to compensate for refractive errors. Discussing the latest alternatives to corrective eyewear with an eye care practitioner will help ensure that any risks are minimized.

All contact lenses are regulated by the FDA as medical devices. By law, people need a prescription to buy them, even for "plano" lenses, which are worn solely to change the appearance of the eye.

In addition, because people have many choices in how, where, and from whom to buy contact lenses, the Federal Trade Commission enforces the Contact Lens and Eyeglass Rules, which help increase the ability to shop around. In this way, the FTC works to prevent fraudulent, deceptive, and unfair business practices regarding contact lenses.

Contact lens quality continues to improve. Advances in materials have made several types of precision contact lenses available for more people. While different types of plastics offer options for replacement and wear schedules, contact lenses are divided into two main groups: soft and rigid gas-permeable (RGP), also called hard contact lenses. From there, the lenses are broken down based on what they're made of, how often they need replacing, and whether they can be worn overnight.

RGP lenses give clearer, crisper vision for some people, according to the NEI. They tend to be less expensive over the life of the lens, but the initial cost often is higher. RGPs last for several years, while soft contacts, depending on the type, are meant to be replaced after short periods. In addition, RGP lenses can be marked to show which lens is for which eye, and they're less likely to tear or rip, making them easier to handle. It may take several weeks, however, to get accustomed to wearing rigid lenses, compared with several days for soft lenses.

Daily-wear soft contacts contain from 25 percent to 79 percent water, are easy to adjust to, and are initially more comfortable than RGPs, due to their ability to conform to the eye and absorb water. Soft lenses aren't as likely to pop out or capture foreign material, such as dust, as hard lenses. There are a variety of soft lens materials available for some people with very sensitive eyes.

The development of hyper-oxygen-transmissible lens materials, for both rigid and soft lenses, has created a new generation of extended-wear contacts that are intended to decrease the incidence of, and the risks for, lens-related eye infections. Silicone hydrogel contact lenses, which, according to the NEI, allow physiological levels of oxygen to reach the ocular surface, have improved the safety of extended- or continuous-wear contacts. Extended-wear lenses are available for overnight, and extended-wear disposables are soft lenses worn from one to six days and then discarded.

In October 2002, the FDA approved a new type of soft contact lens, safe enough to wear continuously for up to 30 nights. These lenses allow six times more oxygen to reach the eye than previously approved lenses. All extended-wear contact lenses, however, carry a greater risk of serious eye infections than lenses that are removed before the wearer retires for the day.

The replacement schedule of contact lenses refers to the length they can safely be worn. RGPs generally are replaced every couple of years because they are made of a durable material, although a prescription change would mean new lenses. Soft contacts come in a wider variety of replacement schedules.

Some special features of many contact lenses, both soft and hard, include bifocals, colored contacts, plano lenses, torics for astigmatism, and UV-blocking contacts.

The rule of thumb for contact lens wearers, says James Saviola, O.D., chief of the FDA's Vitreoretinal and Extraocular Devices Branch, "is to practice good hygiene and follow manufacturers' instructions for proper use, cleaning, and storage of the lenses." Report any signs of infection to your doctor, he adds. People should not wear contact lenses longer than the time prescribed by their eye care practitioner. But whatever is prescribed, Saviola says, be sure to ask for written instructions and follow them carefully. Patient package inserts usually accompany contact lenses, and people who are not offered this information by their doctors should ask for it.

The most serious safety concerns with any contact lens deal with overnight use, or extended wear. Rigid or soft, wearing these types of contact lenses overnight increases the risk of corneal ulcers - infection of the cornea that can lead to blindness. Symptoms include vision changes, eye redness, eye discomfort, and excessive tearing. Saviola advises that keeping lenses clean, replacing them often, and wearing them as prescribed by your doctor minimize the risks of wearing contacts.

Orthokeratology is a nonsurgical procedure that uses RGP contact lenses to change the curvature of the cornea to improve its ability to refract light and successfully focus on objects.

The Ortho-K system was initially approved for daily wear. But in 2002, the FDA approved the lenses for overnight use. A person takes them out in the morning to enjoy the day free of contacts. This method, however, does not produce a permanent result, and Saviola says that a doctor must be certified to fit Ortho-K lenses.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.