Laser eye surgery

Thousands of Canadians are turning to laser eye surgery to correct their vision and eliminate their dependency on glasses or contact lenses. Like all medical procedures, laser eye surgery provides benefits, but poses risks.

Laser eye surgery is the most commonly practiced procedure to correct vision problems caused by refractive errors, including myopia (near-sightedness), hyperopia (far-sightedness) and astigmatism (distorted vision when looking at objects at any distance).

More recently, laser eye surgery has also been used to correct presbyopia (the inability to focus on nearby objects), which is part of normal aging and can be corrected by using reading glasses.

All of these conditions are caused by problems with the way the eye focuses an image on the retina, which is the light-sensitive layer at the back of the eye. A large part of the eye's ability to focus depends on the shape of the cornea, the clear front surface of the eye.

During laser eye surgery, a surgeon uses a laser device to make permanent changes to the shape of the cornea. The laser used most often is the Excimer laser, which produces a beam of ultraviolet light to vaporize tissue. Surgically altering the shape of the cornea can correct mild to moderate refractive errors in most people.

Common laser procedures

The two types of Excimer laser surgery performed commonly in Canada are PRK (Photo-Refractive Keractectomy), first introduced in the early nineties, and LASIK (Laser Assisted in situ Keratomileusis), introduced in the mid-nineties. There are also more recent procedures called LASEK (Laser Epithelial Keratomileusis) and Epi-LASIK.

PRK: The surgeon removes the outer layer of the cornea (epithelium) with a surgical blade or blunt instrument. The laser beam, guided by a computer, is then used to vaporize tiny amounts of tissue under the surface of the cornea. The procedure removes just enough tissue to reshape the cornea in a way that corrects vision. The initial healing process is complete in about a week.

LASIK: This surgery is more complicated. The surgeon first cuts a flap in the cornea with a very sharp blade or laser, and then lifts it and uses a computer-guided laser to remove calculated amounts of tissue from the inside layers of the cornea. Afterwards, the flap is put back and the eye heals more quickly than with PRK.

A recent advance in LASIK surgery is the use of Wavefront technology, which creates a detailed map of the eye. This helps the surgeon make even more precise correction to vision. Your eye surgeon can advise whether this is an option for you.

LASEK: This is a variation of PRK and LASIK. The surgeon cuts the outer layer of the cornea (epithelium) with a fine blade, and uses alcohol to loosen and lift it in a single layer. The laser beam is then directed at tissue under the epithelium, as with PRK. When the laser procedure is finished, the epithelium is put back in place. LASEK is best suited to vision problems that require minor correction. The healing process takes about two weeks.

Epi-LASIK: This is a modified LASEK in which the outer layer of the cornea is removed with a mechanical device using a blunt, rather than a sharp blade.

Benefits and risks of laser eye surgery

Laser eye surgery is performed by highly trained specialists, and in most cases, the results are satisfactory. Some patients feel their lives are vastly improved when their dependence on prescription glasses or contact lenses is reduced or eliminated. However, laser eye surgery also poses certain risks.

With PRK, the risks include:

  • pain, ranging from moderate to severe, for the first few days;
  • hazy vision during the healing process, which usually clears up within the first week after surgery; and
  • regression, which in some cases can cause the eye to regress to its previous refractive error within about six months. If this happens, the patient may need a second operation (called an "enhancement") or may need to start wearing glasses or contacts again.

With LASIK, there is less post-operative pain. However, since this procedure involves cutting into the cornea, there is a greater risk of complications, including the following:

  • dry eyes, which can range from mild to significant and can affect vision;
  • poor quality of night vision due to halos and glare, which could affect your ability to drive at night; and
  • a serious condition called corneal ectasia, which is a weakening and bulging of the cornea. Severe cases may need to be treated with a corneal transplant or implant.

A serious complication that may occur with both PRK and LASIK is corneal infection (infectious keratitis), which may result in significant loss of vision.

The more recent LASEK surgery shares some of the problems associated with both PRK (pain, haze and regression) and LASIK. However, the LASEK procedure reduces the risk of some of the complications associated with cutting a flap in the cornea, such as weakening of the eye and dry eyes.

The risks of laser eye surgery go up significantly for people with certain conditions or lifestyles. When weighing the risks, you should have a detailed talk with the surgeon about the following:

  • your medical condition (including family history) - especially regarding such conditions as lupus, diabetes and keloid formation, as well as any eye diseases (e.g., herpes simplex, glaucoma, dry eyes, eyelid infections or previous eye surgery);
  • whether or not you play sports where you are likely to be hit in the face - after LASIK, there is a risk for years that the flap could dislocate; and
  • your career plans - some occupations (e.g., police officer, pilot) have specific vision requirements that can be achieved with laser eye surgery. Still, it is a good idea to discuss your plans for surgery with current or future employers, as well as your surgeon, to make sure your plans do not affect your prospects for employment.

This article cannot cover potential risks for every conceivable situation. If you are considering laser eye surgery, you must have a thorough talk with your eye surgeon about your options and your individual suitability for different types of procedures. Keep in mind that the long-term effects of laser eye surgery are still unknown.

Other considerations

It is important to have realistic expectations. If you are over the age of 40, you will probably need reading glasses after laser eye surgery. Also, your eyes will continue to change as you grow older, and you may need prescription glasses or contacts again at some point. There is also a chance that you may need a second surgery if you do not get the right amount of correction the first time.

Cost is also a factor, as most health insurance plans do not cover laser eye surgery for vision correction.

Minimizing your risk

Health Canada advises you are more likely to have a successful outcome with laser eye surgery if you:

  • Choose your eye surgeon carefully. The traditional approach is to get a referral from your own eye care professional.
  • Discuss the risks, benefits and your expectations with the surgeon. Read the "informed consent" form thoroughly. Ask questions. Make sure you are a suitable candidate for surgery before you decide to go ahead.

Also, ask your surgeon for a copy of your pre-operative report, which should include information about your pre-operative vision, refraction readings and the shape of your cornea. Keep the report in a safe place for future reference.

After surgery, you can reduce your risk of complications by participating fully in the follow-up care recommended by your eye surgeon.

Health Canada's role

Health Canada regulates the safety, effectiveness and quality of medical devices imported and sold in Canada, including devices used in laser eye surgery. This is achieved through a combination of a pre-market review prior to licensing, and post-market surveillance of adverse events after licensing. As part of this work, Health Canada monitors complaints about medical devices sold in Canada, and communicates safety information about medical devices to health care professionals and the public.

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