 Prescriptions are written out in the number of diopters. One diopter equals a lens that takes rays of light and brings them into focus at one meter. A two-diopter lens brings rays of light into focus at half a meter, and a three-diopter lens, at a third of a meter. Each whole diopter increase reduces the distance at which the lens can bring an object into focus.
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By Sara Gambrill
Judy Myer can't read the clock on her bedside table without her contact lenses. "My eye doctor suggested I get LASIK (laser in situ keratomileusis) done because my eyes are healthy and I have a strong prescription," says Myer, 43. "When my doctor told me he was getting the procedure done on his own eyes, I thought it must be a great procedure." Myer has been saving up for LASIK for two years.
Thousands of nearsighted Americans just like Judy are thinking about undergoing LASIK this year. Why? Because for the first time there is a safe, reliable vision correction procedure that offers a quick recovery. This procedure can free nearsighted people from having to wear glasses and contact lenses for distance vision.
What Does LASIK Do?
LASIK changes the shape of the cornea to mimic the shape of the lens — a concave lens in the case of a nearsighted person — used in a pair of eyeglasses or contact lenses. Lasers are used to change the shape of the eye, more specifically the cornea, allowing the eye to see with near-perfect or perfect vision. (Most patients walk out with somewhere between 20/20 and 20/40 vision.)
The laser treatment allows the cornea to bend, or refract, light coming toward the eye and lens, so that it comes into focus on the retina at the back of the eye. A nearsighted, or myopic, eye is too long, so an object will always come into focus in front of the retina, instead of on it, requiring the person to get closer to the object to see it. LASIK can compensate for this by adjusting the length of the eye.
Penney K. Miller, 46, had LASIK done on both eyes with great results. Miller says there's only one reason she wanted to get the procedure done: convenience.
"I have to travel a lot for my job, and I hated packing up my contacts and the solution for trips. I also hated getting up in the middle of the night and not being able to see," she says.
What Happens During Surgery?
Miller describes the experience of undergoing LASIK, "I had not worn my contact lenses for a few weeks before surgery, as I was told, because contact lenses affect the shape of your cornea. When I arrived for surgery, I was given a sedative and then I was asked to change out of my street clothes and into a special suit that covered me from head to toe. In the operating room, the surgeon put anesthetic drops in my eye and kept my eyelids from shutting with a special instrument, which didn't hurt at all."
During LASIK, the surgeon uses a keratome, a mechanical knife, to slice across the cornea and make a flap that is hinged back to expose a layer of stroma, the middle layer of corneal tissue. A laser vaporizes the amount of tissue needed to give the cornea the correct curve relative to the length of the eye.
"All I could see was the light of the laser," Miller says. "You really don't see anything but that. I could hear some popping sounds too." Then the corneal flap is returned to its original position. "After having the procedure done on both of my eyes, the doctor escorted me back to the waiting room and asked me if I could read the clock on the wall. 'Yes! I can!' I said. I was so excited. I could see so much better right away."
After The Surgery
After the procedure, the patient must wear special protective goggles at night for about a week. It is advisable to go home and rest with the goggles on for a few hours after the procedure. There is a checkup both a day after and a week after. Most people, like Miller, feel no pain during or after the procedure, and they walk out with the vision they want.
Some patients do not get the vision they want with the first procedure and may choose to undergo LASIK a second time. Almost all patients get the vision they want with the second procedure.
LASIK is not without risks, which can include infection, difficulty seeing at night and what is called interface haze (hazy vision at the point where the flap was cut). Blindness is also a risk, as it is with any type of eye surgery. In addition, vision can be overcorrected with LASIK.
Symptoms of dry eye are common after LASIK surgery. People who have dry eyes prior to surgery may notice that their eyes are even drier than before. This increase in symptoms may be temporary or permanent.
In general, the risk for these side effects, however, is low. However, that doesn't mean everybody should rush right out and get it. Not everybody is a good candidate for various reasons.
Who Gets The Surgery?
Should you undergo LASIK? It depends. First of all, LASIK costs around a few thousand dollars per eye and is not covered by insurance.
The real issue with LASIK is that you should not undergo the procedure if your prescription is changing and is not stable. This is common in the teens and early 20s. People in this age group probably should not undergo the procedure because their eyes may have not stopped changing. The teens and 20s are a dynamic time for your eyes, and if you are nearsighted, you can become more so during this stage of life. If you were to undergo LASIK at age 22, for instance, you might have to undergo it again at age 24 because your eye's ability to bend, or refract, light may have changed. However, people aged in the teens in 20s who have a stable prescription are good candidates for LASIK.
The following people, however, should undergo LASIK with caution:
- People with very thin corneas — These people simply do not have enough corneal tissue for the surgeon to work with.
- Candidates for cataract surgery — During cataract surgery, patients are given an artificial lens, which should also correct for nearsightedness. If a patient has had LASIK prior to having cataract surgery, it may be more difficult to calculate the appropriate power of the intra-ocular lens placed inside the eye after the cataract has been removed.
- People with diabetes — The epithelium, or outermost layer of the cornea, is thin in diabetes patients.
- People who have pre-existing dry eye should understand that it can worsen after LASIK.
Another consideration is presbyopia. Presbyopia is a natural process that the eye goes through, typically around age 40. It is when the lens of the eye begins to lose its ability to focus. The lens becomes more rigid and, as a result, less able to change its shape according to whether it's focusing on an object that is near or far. LASIK can change the shape of the cornea, but it cannot stop the lens from becoming more rigid, so people who undergo LASIK before they experience presbyopia will still need to wear reading glasses after about age 40. People older than 40 who wear reading glasses will still have to wear them after undergoing LASIK.
LASIK patients in their 30s who have a relatively weak prescription, such as two diopters, are making a tradeoff. For 10 or 15 years, they can have perfect vision because of LASIK, but when presbyopia sets in, they will need reading glasses. If they do not undergo LASIK, they will not need reading glasses when they are older, but they will still need a light pair of glasses for everyday activities.
LASIK can be a real life-changing experience. Miller says, "I'm very satisfied with the results. I don't have to travel with a lot of extra stuff just so I can see. Swimming is wonderful now. And I don't have to find my glasses in the middle of the night just to see." When asked what her life is like now, Miller responded,"Amazing!"
This article was completed in cooperation with the Kremer Laser Eye Center, headquartered in King of Prussia, Pa.
