Laser eye surgery is a medical procedure that involves the use of laser to reshape the surface of the eye in order to restore normal eyesight without the need to wear glasses or contact lenses. This is done to improve or correct myopia (short-sightedness), hyperopia (long sightedness) as astigmatism (uneven curvature of the eye’s surface).
During laser eye surgery, a computer-controlled excimer laser is used to remove microscopic amounts of tissue from the cornea (the front surface of the eye).
There are five different types of laser eye surgery; Lasik, Lasek, PRK, ALK, and LTK, which are described in more depth below.
Lasik
Lasik (laser-assisted in-situ keratomileuis) is the most common form of laser corrective eye surgery. During the procedure the doctor will cut a “hinged flap” into the cornea, lifting it away from the eye. This allows the doctor to get to the tissue underneath that needs reshaping. A laser is then used to reshape the cornea, flattening or curving it according to where it needs to be corrected. The flap is then folded back into place, healing with a little bit of time – in most cases the patient can return to work the following day.
Lasek or Nu-Lasik
Lasek or Nu-Lasik (laser epithelial keratomileusis) differs from Lasik as it does not cut the cornea. Hence, there is less risk involved as there is no cutting. Lasek uses a technique known as “The New Advanced Surface Ablation” where specific equipment is used to separate the surface corneal layer (epithelium) creating a very thin flap. Re-modeling of the cornea is then achieved using a non heat generating laser called an Excimer. The surface layer is then re-laid and a protective ‘bandage’ contact lens is placed over the ocular surface. Regular anaesthetic and lubricant eye drops are administered throughout the procedure, to ensure optimum results and very little discomfort. The healing phase of Lasek takes a little longer than Lasik yet the long term benefits are much better overall. More than 97% of patients see as well or better after surgery without glasses than previously with their glasses and have significantly less dry eye problems.
PRK
PRK was an earlier version of laser eye surgery and is slowly becoming less common. In PRK, a thin layer on the surface of the cornea is removed and (unlike Lasek or Lasik) is never replaced. The exposed surface of the cornea repairs itself over a period of a few days while covered with a ‘bandage’ contact lens. The cornea continues to heal over a period of a few months, during which time the improvement in vision will become more noticeable. People who have PRK generally have one eye done at a time, due to the length and nature of the healing process.
ALK
ALK (Automated Lamellar Keratoplasty) is used in some cases to treat high levels of myopia (short-sightedness) and mild to moderate Hyperopia (long sightedness). Similar to Lasik, a small flap is cut in the cornea. The doctor then uses microkeratome to remove material under the flap. ALK usually takes less than one hour. ALK, like PRK, is beginning to decrease in popularity due to better results and faster healing rates in other procedures.
LTK
LTK (laser thermokeratoplasty) is a relatively new procedure used to treat Hyperopia (long sightedness) and astigmatism. The heat of the laser beam is used to shrink and reshape the cornea, rather than removing material. The healing time is much faster than other forms because the procedure is less invasive to the eye. However, the improvements do not last as long as other procedures (in general about half of the corrective effect is lost two years after surgery).
The Operation
The excimer laser is a cool laser which doesn’t burn tissue, rather it vaporises small amounts of the cornea every time a beam of the laser is pulsed onto the surface of the eye. The diameter of the laser beam and the number of pulses directed onto the cornea are carefully controlled using computer technology.
The procedure is performed using local anaesthetic eye drops and takes between five and 10 minutes. However, the time taken for the reshaping of the cornea with the excimer laser usually takes less than a minute.
The different sight problems require different treatments for example Myopia requires the central apex or peak of the cornea to be flattened, Hyperopia requires the central apex of the cornea to be made steeper (this is done by applying the excimer laser to the edges of the cornea) and Astigmatism requires the laser to be applied in a more linear fashion to make the cornea more evenly curved.
After the Operation
Many patients can expect; minor discomfort, improved but not immediately perfect sight, will not be allowed to drive home after the surgery.
We suggest that patients should:
1. Use antibiotic and anti-inflammatory medication (in the form of eye drops)
2. Use plastic shields over eye/s for several nights after surgery to prevent rubbing
3. Do not use pressure to rub the operated eye/s
Possible Side Effects and Complications
- Unsuccessful treatment: may be due to treatment or under treatment and patients may need second 'enhancement' procedure
- Dry eyes: a very common side effect of laser eye surgery, patients may require lubricating eye drops
- Delayed headaches: the flap of the cornea may not heal properly. Follow up treatment may be required.
- Infection: treatment with antibiotics may be necessary
- Superficial scarring: this requires a further procedure to fix the scarring
- Excessive thinning of the cornea: this may lead to a return of sight problems and require the use of contact lenses or further surgery
- Sensitive eyes: some report increased sensitivity to glare, which can make driving dangerous
- Blurred vision: 'halos' or rings of fuzzy light may result from treatment.
Long Term
Some people after laser eye surgery will still require glasses or contact lenses to achieve optimum vision, although their natural eyesight should be much improved.