Laser surgery can remove vision problems
By Jeffrey Bramnick, Pure Matters
Laser procedures can help correct refractive errors, or problems caused by an imperfectly shaped eyeball or cornea. (The cornea is the front, transparent part of the eye that bends and focuses light.) Refractive errors cause light from an object to be imprecisely focused on the retina of the eye, causing a blurred image. Refractive errors usually occur in otherwise healthy eyes.
These are the four basic types of refractive errors:
- Myopia or nearsightedness. Close objects appear sharp, but those in the distance are blurred. The eyeball is longer than normal from front to back or the cornea is curved too much, so images focus in front of the retina instead of on it.
- Hyperopia or farsightedness. Distant objects can be seen clearly, but objects up close are blurred. The eyeball is shorter than normal or the cornea is too flat, so images focus behind the retina.
- Astigmatism. Objects are blurred at any distance. The cornea, lens or both are shaped so that images aren't focused sharply on the retina.
- Presbyopia or aging eye. The eye loses its ability to change focus because of the natural aging process. This usually occurs between ages 40 and 50. Refractive surgery cannot correct this problem. It can make distance vision clearer, but it may make near vision worse.
LASIK (laser in-situ keratomileusis) makes up 90 to 95 percent of all laser vision correction surgery and has the broadest range of uses. LASIK is a procedure that permanently changes the shape of the cornea, the clear covering of the front of the eye. A knife called a microkeratome is used to cut a hinged flap in the cornea. The flap is folded back revealing the stroma, the middle section of the cornea. Pulses from a computer-controlled excimer laser vaporize a portion of the stroma and the flap is replaced.
In PRK (photo refractive keratectomy), the surgeon uses a laser to remove the cornea's outer covering and reshape it. This type of refractive surgery gently reshapes the cornea by removing microscopic amounts of tissue from the outer surface. Recovery takes a bit longer than it does with LASIK.
LASEK (laser epithelial keratomileusis) is a surgery that combines LASIK and PRK techniques. It may be used for people who cannot have LASIK. The cornea's surface is loosened with an alcohol solution and moved aside before a laser reshapes the cornea. No flap is cut.
LTK (laser thermal keratoplasty) is a less-invasive laser procedure to correct farsightedness and astigmatism. LTK uses heat to reshape the cornea. The advantage of LTK is that it's a "no touch" procedure, meaning there's little chance of infection or loss of vision.
Is refractive surgery for you?
You should know that health insurers rarely pay for this type of surgery, which is considered cosmetic. Although prices vary a lot experts warn that cost shouldn't be your sole concern.
Laser surgery may not be right for you. "About 10 to 15 percent of adults are not good candidates," says Steven E. Wilson, M.D., director of corneal research at the Cole Eye Institute, part of the Cleveland Clinic. These are factors that indicate you are not a good candidate:
- You aren't a risk taker. Some patients experience complications. No long-term data are available for current procedures.
- It will affect your career. Check with your employer, or military service or professional organization, before undergoing surgery. Some jobs prohibit certain refractive procedures.
- You required a change in your contact lens or eyeglass prescription in the past year. This is called refractive instability. People likely to have refractive instability include those in their early 20s or younger; those whose hormones are fluctuating because of a disease such as diabetes; women who are pregnant or breast-feeding; and those who are taking medications such as steroids.
- You have a disease or are on medications that may affect wound healing. Illnesses include autoimmune diseases such as rheumatoid arthritis, HIV and diabetes. Medications include retinoic acid and steroids.
- You have an eye disease.
- You participate in contact sports such as boxing, wrestling or martial arts in which blows to the face and eyes are common.
- You are not an adult. No lasers are approved for children or teens under 18.
Besides the illnesses listed above, other diseases may negatively affect the outcome of LASIK surgery:
- Herpes simplex or herpes zoster (shingles) around the eye area
- Glaucoma, ocular hypertension or are at risk for glaucoma
- Eye injuries or previous eye surgeries
- Keratoconus, a thinning disorder of the cornea
These are other risk factors that may affect the outcome of your surgery:
- Large pupils. Younger patients and patients on some medications may have large pupils in dim light. This can cause glare, halos, starbursts and double vision after surgery. The symptoms may be severe enough to hamper normal activities such as driving.
- Thin corneas. Refractive surgery done on a cornea that is too thin may lead to blindness.
- Previous refractive surgery. Talk to your doctor if you've had RK, PRK, LASIK or another refractive procedure. Additional surgery may not be recommended.
- Dry eyes. LASIK surgery can aggravate this condition.
- Under or over correction can occur if too little or too much tissue is removed.
- Astigmatism can occur if an uneven amount of tissue was removed.
- Glares, halos or double vision can result.
Finding a good surgeon
Only ophthalmologists are permitted to perform LASIK. Ask your eye doctor or optometrist for a referral to an ophthalmologist who performs LASIK. Ask for a referral from an ophthalmologist who does not do refractive surgery. You can also visit the American Academy of Ophthalmology's website (http://www.aao.org), which offers a list of its members who perform LASIK. Ninety-five percent of all ophthalmologists are AAO members. Ask your surgeon the following questions:
- How long have you been doing LASIK surgery?
- How much experience do you have with the LASIK procedure?
- How do you define success? What's your success rate?
- What is the chance for me (with my correction) to achieve 20/20?
- How many of your patients have achieved 20/20 or 20/40 vision?
- How many patients return for enhancements?
- Which laser will you be using for my surgery?
- What's involved in after-surgery care?
Make sure your surgeon is using a laser approved by the U.S. Food and Drug Administration. The FDA has approved five lasers for LASIK; they are manufactured by VISX, Summit, Bausch and Lomb, Nidek and ATC.
Many people don't have 20/20 vision after surgery, but most are 20/40 or better. Eight to 10 percent, Dr. Wilson says, need an added procedure. Some need eyeglasses or contact lenses to make up for over- or under-correction.
Complications include night glare, infiltration of the cornea, ripples, infection, regression of correction, under correction, loss of visual acuity, dry eyes, difficulty in fitting contact lenses for additional correction and the need for re-treatment. The complication rate is around 10 percent.
If you're a good candidate for a LASIK procedure, have realistic expectations and choose the right surgeon, chances are very good that you will do well.