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Refractive Eye Surgery

Also known as: LASIK Surgery

Until fairly recently, glasses and contact lenses were the only ways to correct refractive errors. Laser assisted in situ keratomileusis (LASIK), a type of refractive surgery that permanently changes the shape of the cornea, is now an option for many people.

How the eye works

For you to see clearly, the cornea – the transparent tissue that covers the iris (or colored part of the eye) and the lens (located behind the iris) – must bend, or refract, light rays so they focus on the retina, a layer of light-sensitive cells lining the back of the eye. The retina converts light rays into impulses that are sent through the optic nerve to the brain, where they are recognized as images. If the light rays do not focus on the retina properly, the image you see is blurry. This problem is called a refractive error. Glasses, contacts and refractive surgery correct or reduce the refractive error by focusing light rays closer to or directly into your retina.

Types of refractive errors

Myopia
If your eye is longer than usual or the cornea and lens have too much focusing power, light rays focus in front of the retina instead of on it. This refractive error is called myopia, or nearsightedness, and means you have a heard time seeing objects at a distance.
Hyperopia
If you eye is shorter than usual, or the cornea and lens lack the necessary focusing power, light rays focus beyond the retina. This refractive error is called hyperopia, or farsightedness, and means you can’t see close objects clearly. A young person may be mildly farsighted but unaware of it because lens the lens is flexible and compensates for the error by bringing the light rays forward and onto the retina.
Astigmatism
Astigmatism occurs when the curve of the cornea is uneven – steeper in one direction than in the other like the back of a spoon. This uneven curve causes light rays to focus on may points on the retina, distorting both near and far vision.
Presbyopia
If you have presbyopia, or “aging eye,” close objects appear blurry. Presbyopia usually begins around age 40 when the lens begins to harden and lose its elasticity. This refractive error is usually corrected with bifocals or reading glasses. Nearsighted people with presbyopia can often read without glasses, but farsighted people will probably need reading glasses around age 40. presbyopia cannot be corrected with refractive surgery.

The good LASIK candidate

LASIK is intended for people who want to minimize their reliance on glasses or contact lenses. People looking for perfect vision without glasses or contacts run the risk of being disappointed with LASIK.

If your refractive error falls outside acceptable guidelines, it may not be possible for you to have LASIK. However, other types of refractive surgery (including some techniques that are still being developed) may benefit you in the future. Dr. David Liang can discuss this with you further.

A good candidate for LASIK must be free of eye disease and have a prescription for glasses or contact lenses that as been relatively stable for at least six months. Although there is no upper age limit for having LASIK, people under 18 are not good candidates because their vision is still changing. Pregnant women, people with diabetes, people using oral prednisone, or those who have a poorly controlled autoimmune disorder such as rheumatoid arthritis or lupus, or a history of ocular herpes, should probably not have LASIK either.

If you have specific occupational goals, you should ask prospective employers about refractive surgery regulations before making your decision.

The first step

A thorough eye exam is the first step. Your refractive error, current vision prescription and best-corrected vision (the last line on the eye chart you can see wearing your glasses or contacts) are determined during your visit. The outside of your eye is checked for infections, eyelid abnormalities or tear duct problems. Your pupil is evaluated and measured and a pressure check for glaucoma is performed. Through dilated pupils, the inside of your eye is examined to detect problems such as cataracts or retinal disease.

Dr. Liang will measure your cornea with precise computerized topographical maps. These maps help your surgeon determine if LASIK is right for you. Another measurement of the corneal surface is taken with a device called a keratometer. The thickness of the cornea is measured with a pachymeter to make sure that your cornea is not too thin for this type of surgery.

Your dominant eye is identified, since this may influence which eye is treated first and how much each eye is treated. Some people choose to have LASIK performed on both eyes at the same time to eliminate visual imbalance between surgeries. Others choose to have one eye done at a time. You and Dr. Liang should make this decision together.

You will be advised to stop wearing contact lenses for a period of time before surgery: 2 weeks for soft contact lenses and 4 weeks for rigid gas permeable or hard contact lenses. Contact lenses can temporarily change the shape of the cornea, and it is important that your cornea be in its natural shape on the day of surgery. You will also be advised to avoid makeup, lotions or perfumes for a few days prior to surgery. These products can interfere with the laser treatment or increase the risk of infection after LASIK. Depending on your occupation, you may need to take one to several days off. Be sure to consider this possibility when scheduling surgery.

How is LASIK performed

In the outpatient surgical suite, you will lie down in a reclining chair where your eye is draped and numbed with a few drops of topical anesthetic. An eyelid speculum is positioned between the upper and lower eyelids to keep them open and prevent you form blinking. Your eye is moistened and a suction ring is put into place. The suction ring lifts and flattens the cornea and helps keep your eye from moving in preparation for surgery. From the time the suction ring is put on the eye until it is removed, your vision will dim or go black.

The microkeratome, a cutting instrument, is then attached to the suction ring. The microkeratome blade moves across the cornea, stopping at a preset point far enough from the edge of the cornea to create a hinged flap of paper-thin corneal tissue.

The microkeratome and the suction ring are removed from the eye, and the flap is lifted and folded back. (As the flap is moved, your vision will fluctuate.) The exposed cornea is dried, and the laser is positioned over the eye. While you stare at a blinking light above you, the laser sculpts the exposed corneal tissue. Using pre-programmed information about your eye obtained during your previous visit, the computer-assisted laser delivers short pulses of ultraviolet light. The laser light breaks apart molecular bonds in the protein of the stroma, the middle layer of the cornea, and vaporizes microscopic amounts of tissue.

After reshaping the cornea, your surgeon will place the flap back into position and smooth down the edges. The flap adheres on its own in two to three minutes without stitches. A see-through shield is placed over the eye to protect the flap.

Although the procedure is usually painless, some people experience discomfort or pressure when the speculum is placed between the eyelids and again when the suction ring is applied to the eye.

What happens after surgery

You may experience a mild burning or itching sensation, or feel as if something is in your eye, for up to a few hours after the procedure. Pain medications can be prescribed if needed.

Vision will often be blurry the day of surgery and improve considerably by the next day when you return for your post-operative exam. Many people report almost perfect vision when the shield is removed the day after surgery.

The following side effects are possible, but usually disappear over time:

Discomfort or pain
Hazy or blurry vision
Scratchiness
Dryness
Glare
Haloes or starbursts around lights
Light sensitivity
Small pink or red patches on the white of the eye

After surgery, avoid swimming, hot tubs and whirlpools for two weeks. Do not drive until your vision has improved enough to enable you to drive safely. Above all, do not rub your eyes. If you experience any bothersome symptoms or unusual side effects, such as pain or extensive redness, report these symptoms to your ophthalmologist immediately.

Potential problems after LASIK

More than one million people in the United States have had LASIK, most very successfully. However, as with any surgery, complications can occur. Many can be easily treated, but a serious complication, although rare, could result in poorer vision with glasses or contacts than you had with glasses or contacts before surgery.

Over-correction or under-correction are among the more commonly encountered complications. Fortunately, these problems can often be improved with glasses, contact lenses, or additional laser surgery. Although rare, over-correction can sometimes be permanent. Second surgeries to treat under-correction or over-correction are usually performed some months after the initial surgery, when your vision has stabilized.

Many patients experience dry eyes. This condition is generally temporary and is treated by using lubricating eye drops. Sometimes, tiny plugs can be inserted into the tear duct opening to keep moisture in the eye longer. These plugs are inserted painlessly and are not visible.

The microkeratome is a complicated device with many moving parts. New advances in the microkeratome are minimizing the risk of flap complications, but a microkeratome malfunction can lead to a poorly formed flap and ultimately loss of best-corrected vision. If a malfunction occurs, the procedure is stopped and the laser surgery postponed.

The flap can also be dislodged (remember, there are no stitches), or heal poorly because of epithelium (surface cells of the cornea) or debris under the flap.

It is also possible, although very rare, for the laser treatment to be delivered to the stroma off-center or irregularly, which can compromise the visual result. Infection and scarring of the cornea, should they occur, can result in permanently decreased vision.

Informed consent

The process of learning about the risk, benefits and alternatives related to a surgical procedure is known as the “informed consent” process. Dr. Liang will ask you to sign an informed consent form before you have LASIK. Give yourself time to review the form carefully. Remember, as with any surgical procedure, it is impossible to guarantee results.

Glasses after LASIK

Hundreds of thousands of people who have had LASIK are happy with the results. The majority are free of glasses or contacts for most activities and will be until middle age when they will need reading glasses to correct presbyopia, the loss of close-up focusing power. After LASIK, some people may wear glasses for certain activities that require the best possible vision, like driving at night.

With or without refractive surgery, almost everyone needs reading glasses around age 40. people with low to moderate myopia (-1 to –5) are an exception. They are able to take their distance glasses off to do things that require close-up focusing, like reading, using a computer, putting on makeup, threading a needle or tying flies for fishing. If you are one of these people and you are considering LASIK, it is important to understand that you will lose this advantage after LASIK. As you reach middle age, you too will need reading glasses or magnification.

For some people having LASIK surgery, monovision is a technique that can delay or prevent the need for reading glasses. Originally developed for contact lens wearers, monovision corrects one eye for distance and the other for close-up. People who have enjoyed monovision with contacts may want to discuss this option with their refractive surgeon. Some people do quite well wit it, while others cannot tolerate it. You and your ophthalmologist should discuss such options thoroughly before deciding what is best for you.

After LASIK, some people choose to have a second surgery, referred to as an enhancement, to further refine their vision and reduce their dependence on glasses or contact lenses. Although very rare, a complication could occur during LASIK surgery or LASIK enhancement surgery that would result in “loss of best-corrected visual acuity.” This means that you would not be able to see as well after surgery, even with glasses or contacts, as you did with glasses or contacts before surgery.

The majority of people who have LASIK achieve somewhere between 20/20 and 20/40 vision without glasses or contacts. Vision measuring 20/40 is good enough to pass a driving test in most states. However, 20/40 vision might be noticeably different if you were used to seeing 20/20 with glasses or contact lenses before LASIK. Vision can usually be improved to 20/20 by wearing glasses or contact lenses.

Other refractive surgery options

Photorefractive Keratectomy (PRK): An excimer laser surgery procedure to reduce low to high myopia, low to moderate hyperopia, and astigmatism.
Intrastromal Corneal Rings: Crescent-shaped plastic segments surgically implanted in the cornea to reduce mild nearsightedness.
Laser Assisted Subepithelial Keratomileusis (LASEK): Surgery similar to LASIK, but with a much thinner flap.

We do not currently perform LASIK surgery at our facility. However, in the near future, Dr. David Liang, our Corneal Surgery specialist, will begin accepting appointments for consultation on this procedure. Please call (717) 531-5690 to request a consultation appointment with him.

This information has been designed as a comprehensive and quick reference guide written by our health care reviewers. The health information written by our authors is intended to be a supplement to the care provided by your physician. It is not intended nor implied to be a substitute for professional medical advice.

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