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A Brand New Perspective

A Brand New Perspective

Models, actors, sportsmen get their myopia surgically corrected to improve their performance. You can too, if you don't fancy the burden of wearing glasses. Vincent Leong of HealthAnswers weighs the pros and cons of refractive surgery.

Danielle Tham, a 28-year-old graduate student, used to wear sunglasses to shield her eyes from the daylight everywhere she goes. With each of her eyes around 1100-degrees myopic, Danielle's eyes were over-sensitive. She also had astigmatism in both her eyes. Her eyes shed tears easily. Her spectacles were made of heavy glass, and if she didn't want to wear them, she needed to get expensive, specially made contact lenses, as disposable ones do not correct astigmatism. "The worst was the headaches." Danielle says. "With the heavy glasses, I used to get terrible headaches when I strained my eyes."

The good news is Danielle does not need to wear glasses anymore. After she underwent a LASIK surgery at Singapore National Eye Centre (SNEC), Danielle regained her normal vision. She can now go swimming without worrying about her spectacles.

Danielle is one of many young, upwardly mobile women who choose laser vision surgery -- a relatively new and popular refractive surgery that uses laser to correct a person's vision or refractive errors -- over a life-time of wearing spectacles or contact lenses. Over 60 percent of the patients who seek laser vision surgery at SNEC are women in their 20s or 30s. Many are executives and office workers. Is this a sign that laser vision surgery is a real option for people who needs glasses, and not just for athletes or movie stars?

What Is Refractive Surgery?
Refractive surgery refers to various surgical procedures that can be used to correct a refractive error in a person's eye. Common refractive errors are myopia (short-sightedness), hypermetropia (long-sightedness) and astigmatism.

Different surgical tools may be used in refractive surgeries. Surgeons can use surgical knives, lasers, or implantation of devices (such as artificial lenses) to correct the refractive errors.

Usually, in refractive surgeries, the cornea is flattened to correct myopia. To correct hypermetropia, the cornea is steepened. To correct astigmatism, the patient's cornea is smoothened of irregularities.

Since the early 1990s, the development of excimer laser surgery has been remarkable, making other refractive surgeries almost obsolete. However, laser vision surgery is not yet the cure for all refractive problems. It is still not reliable in correcting presbyopia, which is part of the ageing process. Clinical investigations are now being done.

There are principally two methods in excimer laser vision surgeries: Photorefractive Keratectomy (PRK) and Laser In-situ Keratomileusis (LASIK).

During PRK, surgeons make use of the very precise, computer-controlled excimer laser to sculpt the surface of the cornea, reshaping it.

0620a"The cornea is the transparent window of a person's eye. It is made up of different layers. In PRK, an excimer laser is used to sculpt the cornea, removing a thin layer of skin tissue from the surface," says Consultant Ophthalmologist Dr Chan Wing Kwong, who is head of Refractive Surgery Service at SNEC. "Just like carving the spectacle correction on the cornea."

In LASIK, the work is done inside the cornea. First, a microkeratome, a surgical instrument for shaving microscopic layers of tissue, is used to slice a thin flap of corneal tissue. One side of the flap is left connected to work as a hinge. This flap is then folded open, exposing the interior of the cornea. An excimer laser is used to sculpt at the exposed inner layer to correct the refractive error, before the flap is replaced.

The difference between PRK and LASIK is that LASIK leaves the outermost protective layer of the eye untouched, while PRK requires the surgeon to gently scrape at it.

According to Dr Chan, both PRK and LASIK work very well. PRK is simpler, faster and can be done at a lower cost. On the other hand, LASIK requires a shorter time for recovery. This is because for LASIK, the actual sculpting is done inside the cornea instead of its surface, resulting in less irritation to the patient's eye, and less chance of scarring.

"Normally, for a patient to get back his reliable vision, PRK takes five days to a week, and for patients going through LASIK, it can be as short as a day," says Dr Chan.

0620bDr Chan recommends PRK for candidates with low to moderate degrees of refractive error of myopia and LASIK for those with high degrees.

Undergoing PRK Or LASIK
PRK and LASIK are outpatient procedures, meaning that the patient does not need to be admitted into a hospital. Of course, patients should not drive immediately after the procedure. The laser treatment itself usually takes less than a minute, while the entire procedure takes around five to 10 minutes.

Anaesthetic drops are used in the eye, and a device is used to hold the eyelids open. The patient is asked to focus on a light, and he should not feel any pain.

"It was scary," says Danielle of her experience. "But I did not feel a thing. I looked into the light when the doctor asked me to, I could see a flap flipped out from my eye. But it was over before I know it. And I could see clearly almost immediately!"

At SNEC, Dr Chan operates on one eye for his patients, and then operates on the other the very next day.

"Many surgeons operate on both eyes at one go and get very good results," says Dr Chan. "We tend to be more conservative here [SNEC]. We usually wait 24 hours, or a few days, before we operate on the other eye to ensure that there is no serious complications."

After the procedure, a patient is given antibiotic eye drops. He should probably rest a while before leaving. The patient probably already notices clearer vision after this, and his vision should stabilise as the weeks go by.

Is Laser Vision Surgery For Anyone?
An ophthalmologist, an eye specialist, always gives a patient a thorough eye examination before deciding if the patient is suitable for laser vision surgery. The specialist needs to determine if the patient's eyes are healthy. A machine called a corneal topographer is used to photograph and electronically map out the contour of the cornea. The surgeon can then use this map to plan for the most precise results possible.

The ophthalmologist looks for glaucoma, cataracts, and other disqualifying conditions whenever he is determining if a patient is a suitable candidate. Generally, a person who has healthy corneas and is over 21 is ideal. Laser vision correction is not recommended for women who are pregnant. A person who wishes to go through PRK or LASIK should also not have a significant increase in spectacle prescription within the last 12 months.

Eye specialists also give a comprehensive pre-surgery consultation before the actual procedure so that patients get a good understanding of the whole process.

The Risks
There are always risks and complications in surgeries, and laser vision surgeries are no exceptions.

Although rare, there is a slight possibility of over-correction and under-correction of the refractive error in PRK and LASIK. When there is under-correction or over-correction, patients may need to go through re-treatment, or minor presciption spectacles or contact lenses may be possible options.

Some potential side-effects of PRK and LASIK include corneal haze, halos, light sensitivity or glare (distortions), corneal scarring (prolonged corneal haze), delayed epithelial healing (abnormally slow healing), regression (refraction error returning), and infection.

Other rare complications are cataract, elevated intraocular pressure, double vision, induced astigmatism and drooping of the eyelid.

"Patients have to weigh the pros and cons between taking the risk of surgery and the desire to live life without wearing glasses or contact lenses," warns Dr Chan.

"Laser vision surgery is a very elective surgery, and it is mainly functional. Most of the time, patients can live with wearing glasses or contact lenses," he adds. "Of course, if someone is happy with wearing glasses, that is the cheapest and safest choice."

Dr Chan stresses that the success rate of excimer laser surgery is comparably high and predictable, but it does not always create perfect vision. At SNEC, about 90 percent of the patients who go through the procedure with up to 600 degrees of myopia, have their vision restored to 6/12 (the minimum requirement for driving on the roads here) or better; and about 40 percent regained 6/6 or perfect eyesight. As for patients with myopia above 600 degrees, about 70 percent of them regain 6/12 vision, and about 20 percent have their eyesight restored to perfect.

"The predictability and safety of excimer laser surgery decreases as the amount of myopia increases," Dr Chan explains. "The lower the degree of the refractive error, the easier it is for the patient to regain perfect vision. The higher it is, the harder it is for him to regain his perfect vision. Patient with up to 500 or 600 degrees usually have very good results from this procedure."


Excimer : Derived from the words "excited" and "dimmers"
Laser : Light Amplification by the Stimulated Emission of Radiation
LASIK : Laser In-situ Keratomileusis
PRK : Photorefractive Keratectomy

*All graphics and pictures by courtesy of SNEC.

Date reviewed: 20 June 2000

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