Vision Problems

Implant, Thermal Procedures
by Food and Drug Administration (FDA)

(Page 5 of 5)

Implant Procedures

Corrective artificial lens implants give people who don't want to bother with eyeglasses or manual insertion of contact lenses another option to consider.

Intrastromal corneal ring segments are semicircular pieces of plastic that are implanted within the cornea to treat mild forms of myopia. They also are sometimes used for other conditions affecting the cornea. The inserts are designed to change the shape of the cornea by adjusting the focusing power of the eyes so that light is focused onto the retina. A small incision is made near the upper edge of the cornea, in which the ring segments are inserted. The incision is closed with two small sutures that are usually removed two to four weeks after surgery.

While tissue removed during laser eye surgeries cannot be replaced, the intrastromal corneal ring segments are removable.

Phakic Intraocular Lenses are new devices made of plastic or silicone, approved by the FDA for correcting nearsightedness. These thin lenses are implanted into the eye to help reduce the need for glasses or contact lenses. A small incision is made in the front of the eye, in which the phakic lens is inserted. Phakic refers to the lens being implanted into the eye without removing the eye's natural lens. Since phakic IOLs involve entering the eye, unlike LASIK and PRK, the risk of complications is higher.

Phakic lenses are intended to be permanent. If a cataract develops, however, the natural and phakic lenses would be removed and replaced with artificial lenses, says Kesia Alexander, Ph.D., chief of the FDA's Intraocular and Corneal Implants Branch. But, she adds, "there's no guarantee that the eye will return to its previous level of vision." Alexander also says that while phakic lenses are a good alternative for people who are very myopic and can't be corrected with LASIK, "there's no guarantee that you won't always be able to go without glasses."

Thermal Procedures

Conductive keratoplasty uses radio frequency energy, instead of a laser, to bend the cornea. Also known as "blended vision," CK corrects for hyperopia. By overcorrecting the cornea, CK causes the eye to become nearsighted. "CK achieves its correction of presbyopia," says Beers, "by inducing monovision with one nearsighted eye."

CK does not involve making an incision, but instead, a tiny probe releases controlled amounts of very low heat from radio frequency energy, causing the outside area of the cornea to tighten like a belt, making the central cornea steeper. CK causes little or no discomfort or irritation, and vision improvement is almost instantaneous. Unlike other types of refractive surgery, such as LASIK, however, correction from CK may be temporary and re-treatment may be necessary.

Other Refractive Surgery Procedures

Accommodative and multifocal IOLs are used to treat nearsightedness, farsightedness, and the inability to focus up close because of age. These artificial lenses are surgically implanted in the eye. Unlike the phakic IOLs, which are implanted in front of the eye's natural lens, accommodative and multifocal IOLs actually replace the eye's natural lens once a cataract has developed. These lenses enable the eye to regain its focusing and refractive ability.

Monovision is a corrective technique used to treat people with presbyopia. The intent is for the person to use one eye for distance viewing and one eye for near viewing. Having each eye configured for different focusing distances can reduce or eliminate the need for eyeglasses or contact lenses.

The practice was first applied to contact lenses, and more recently to LASIK and other surgeries. In refractive surgery, the technique treats one eye to focus at close proximity, while the other eye is left untreated or, if needed, treated to be able to focus at a distance. This method may be difficult to adjust to at first but, according to the International Society of Refractive Surgery, about six to eight weeks after the monovision procedure, most people's brains are able to adjust to the different focusing ability of the eyes.

The FDA recommends that anyone considering monovision try the contact lens procedure first, as a trial run, before having the surgery, which is permanent. Also, it's important to check state drivers' license requirements with monovision.

Eyeglasses - The Reliable Standby

In some cases, modern technology can provide the best vision correction option. In those cases in which it can't, eyeglasses may be the way to go. Glasses correct refractive errors by adding or subtracting focusing power to the cornea and lens. The power needed to focus images directly on the retina is measured in diopters. This measurement is also your eyeglass prescription.

Like contact lenses, glasses come in all shapes and sizes, offering an array of choices for both function and fashion. Eyeglass frames, for example, are more durable and tout materials such as titanium and new "memory metals." Manufacturers are making lenses that are thinner, stronger, and lighter. And lens options include antireflective coating, light-changing tints, line-free (progressive) bifocal, and polycarbonate - the most impact-resistant lens material available.

Regular eye exams are important because they can detect early signs of disease and refractive error long before either leads to vision impairment. Doctors recommend that everyone have an eye exam shortly after birth, and at least every few years until age 40. After that, the eyes should be routinely checked every two or three years. People with diseases such as diabetes and hypertension should have their eyes checked more frequently.

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.