Laser Eye Surgery
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.
Types of Laser Surgery
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 -ILASIK.
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 called a microkeratome, and then lifts this flap and uses a computer-guided laser to remove calculated amounts of tissue from the inside layers of the cornea bed. Afterwards, the flap is put back and the eye heals much 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.
ILASIK: This is a modified LASIK in which the outer layer of the cornea is removed to form a flap . Another laser is then used to generate the visual correction using Wavefront technology. This procedure is used at the leading eye institutes including Duke University Medical School, the Wilmer Eye Institute at Johns Hopkins, the Bascom Palmer Eye Institute at University of Miami, and Stanford University.
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.
Benefits and 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 ILASIK, there is less post-operative pain. The ILASIK 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.
• dry eyes, which can range from mild to significant and can affect vision;
- 2 % experience poor quality of night vision due to halos and glare, which could affect your ability to drive at night
- a serious condition called corneal ectasia, which is a weakening and bulging of the cornea if cornea thickness goes beyond 350mu
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.
If you are considering laser eye surgery, a thorough talk with your optometrist and eye surgeon about your options and your individual suitability for different types of procedures is warranted.
contraindications
- your medical condition (including family history) - especially regarding such conditions as lupus, diabetes and keloid formation, collagen vascular diseases, and active ulceration 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.