More Than a Fix for Nearsightedness. LASIK & PRK Correct Farsightedness and Astigmatism as Well

LASIK is the most popular corneal refractive procedure worldwide, with more than 700,000 procedures performed each year in the U.S. alone. LASIK produces excellent results when performed by a skilled eye doctor, and although it’s not an ophthalmologic cure-all, the technology is adaptable to a wide variety of vision problems.

How LASIK Works

The concept behind LASIK — or laser assisted in situ keratomileusis — is fairly straightforward. Your cornea accounts for much of your eye’s focusing ability, and irregular or abnormally shaped corneas cause blurry vision. Reshaping the corneas with LASIK can often compensate for blurred vision due to these abnormalities, which doctors call refractive errors. During a LASIK procedure, your doctor uses a blade or laser to create a flap on the front of your cornea. The flap is carefully folded back, and the underlying cornea is reshaped with a laser. The flap is then returned to its original position. No stitches are required, and postoperative discomfort is usually minimal. Most people’s vision is markedly improved within two to three days, although full vision stabilization may take longer.

Myopia

People with myopia, or nearsightedness, have trouble focusing on far-away objects. If you are nearsighted, or myopic, without corrective lenses you have problems seeing well at a distance, but may be able to see clearly up-close. Nearsightedness is a refractive error caused by the cornea being too curved, resulting in light being focused in front of the retina rather than on the retina. Laser vision surgery for the correction of nearsightedness is accomplished by flattening the central cornea, thus allowing light to focus correctly on the retina. During the procedure, pulses of cool, ultra-violet light are emitted from a computer-guided Excimer laser to remove corneal cells according to your unique prescription. More LASIK procedures are performed to correct myopia than any other vision problem. According to a 2011 review in BMC Ophthalmology, over 80 percent of laser refractive procedures performed at Johns Hopkins Wilmer Eye Institute during one quarter of 2009 were done on myopic patients, 65 percent of whom opted for LASIK. While most LASIK patients are primarily interested in correcting nearsightedness, the procedure is also commonly used to deal with other refractive problems.

Hyperopia

People with hyperopia, or farsightedness, have trouble focusing on nearby objects. If you are farsighted, or hyperopic, without corrective lenses you have problems seeing well up close, but are able to see objects in the distance more clearly. Farsightedness is a refractive error caused by the cornea being too flat, or the eye being too short, preventing light from focusing on the retina. The laser vision correction of farsightedness is accomplished by steepening the central cornea, thus allowing light to focus correctly on the retina. During the procedure, pulses of cool, ultra-violet light are emitted from a computer-guided Excimer laser to remove corneal cells according to your unique prescription. Until recently, LASIK was less satisfactory for treating hyperopia than myopia, and farsighted people were more likely to experience glare and halos following the procedure. However, a study published in the May 2010 issue of Clinical Ophthalmology demonstrated a reduction in these minor complications when a broader area of the hyperopic patient’s cornea is treated with laser. These findings are representative of the ongoing research that continues to improve LASIK’s utility for correcting a variety of refractive problems.

Astigmatism

If you have astigmatism, without corrective lenses you experience overall blurry vision, shadowing, or distortion of your vision. Astigmatism is a refractive error caused by the cornea having an oval, or football shape resulting in light focusing on multiple points around the retina rather than a single point on the retina. If the surface of your cornea is shaped more like a football than a baseball, the light entering your eye bends unequally. This produces sharp images in some areas of your field of vision and fuzzy images in others. The type of astigmatism you have is determined by the direction and extent corneal warping. Many people with astigmatism also have myopia or hyperopia. The LASIK correction of astigmatism is accomplished by smoothing out the irregularities of the cornea at the precise points of astigmatism, thus allowing light to focus correctly on the retina.

According to W. Neil Wills, M.D., a LASIK doctor, most forms of astigmatism — including those associated with myopia or hyperopia — can be effectively treated with LASIK. A condition called irregular astigmatism is an exception.

Presbyopia

Some amount of presbyopia, or “aging eyes,” is universal in older adults. As you age, the lenses inside your eyes gradually lose flexibility. This becomes noticeable at about age 45 to 50 with loss of the ability to focus on nearby objects. Unlike other refractive errors that are due to structural problems with your focusing mechanism, presbyopia is caused by a loss of your eyes’ ability to change focus. When presbyopia becomes significant, most people require reading glasses or bifocals to read or work at a computer.

Dr. Wills explains that LASIK can treat your eyes, but it cannot affect your age. If you have presbyopia and want to reduce your dependence on corrective lenses, your eye surgeon might suggest a technique called “monovision LASIK,” which corrects one eye for reading and the other for distant vision. Monovision LASIK generally allows you to see well at all distances, but it may impair your depth perception. Although the thought of having your eyes focused at different distances might seem disconcerting, Dr. Wills reports that 90 percent of patients adjust to monovision LASIK within a few months.

High Satisfaction Rate

More than 95 percent of patients undergoing LASIK are satisfied with the results of their surgery, regardless of their original vision problem. Millions of people have undergone LASIK, and even the NASA and U.S. military have adopted the procedure for their aviators. Before you proceed with laser vision correction, schedule a consultation with a LASIK doctor who will perform a thorough evaluation to determine if LASIK is a good option for you.

References

American Academy of Ophthalmology Clinical Updates: Demographics of Refractive Surgery Patients and Market Trends: http://www.aao.org/vp/edu/refract/v1m5/refractive_management_v1m5.pdf

Eye Surgery Education Council: More than 95 Percent of LASIK Patients Report Satisfaction Rate Worldwide: http://eyesurgeryeducation.org/resources-news.php?id=30&type=news

Email Interview with W. Neil Wills, MD, FACS

American Family Physician: LASIK:  A Primer for Family Physicians: http://www.aafp.org/afp/2010/0101/p42.html

BMC Ophthalmology: Trends in Refractive Surgery at an Academic Center: 2007 – 2009: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3115925/

Clinical Ophthalmology: Predictability and Stability of Refraction with Increasing Optical Zone Diameter in Hyperopic LASIK: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2874273/

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