Laser Vision Correction (LASIK, PRK, SMILE)

What is Laser Vision Correction (Refractive Surgery)?

Laser vision Correction (or Refractive Surgery) is one of the most common elective procedures done worldwide which involves the utilisation of a computerised excimer laser to reshape the corneal surface in order to improve vision.

What are the different types of Laser Vision Correction?

Currently, there are three main types of Laser Vision Correction:

  • LASIK (Laser-Assisted in Situ Keratomileusis)
  • PRK (Photorefractive Keratectomy)
  • SMILE (Small Incision Lenticule Extraction)

LASIK (Laser-Assisted in Situ Keratomileusis)

LASIK (Laser in-situ keratomileusis) is the most popular type of laser vision correction procedure, which is used to correct nearsightedness (myopia), farsightedness (hyperopia), presbyopia (loss of ability to focus on nearby objects), and astigmatism (improper curvature of the eye’s surface).

The procedure works by remoulding the cornea (transparent dome-shaped front part of the eye), allowing proper focusing of the light that passes through the cornea onto the retina (light-sensitive membrane at the back of the eye).

The surgery consists of creating a flap in the cornea with a laser and reshaping the underlying corneal tissue. The flap is then replaced and within several hours the surface layer of the cornea (epithelium) will grow over the cut edge of the flap to seal it into position. After a few days, collagen bonds form within the cornea around the edge of the flap and sealing it permanently.

What are the pre-operative procedures?

To prepare for LASIK you will need to:

  • Stop wearing contact lenses and switch over to glasses at least a few weeks before the procedure
  • Avoid using eye makeup the day before and day after surgery
  • Maintain good hygiene of the eyelashes to reduce infection risk

Your ophthalmologist will review your medical history and conduct a detailed eye examination to assess the shape and thickness of your cornea, which helps to determine the exact regions that need reshaping. The latest technology (wavefront-guided) enables your ophthalmologist to further customise the standard procedure to your individual eyes by using a scanner to generate a detailed map of your corneal surface (topography).

How is LASIK performed?

You will be given medication to relax you. Eye drops will be instilled to numb your eyes. Your ophthalmologist will use a special instrument to keep your eyes open during the procedure. Next, you will be asked to focus on a source of light in order to keep your eye fixed during the procedure. Your ophthalmologist will then use a special (Femto-second) laser to cut a thin flap in the cornea with a little hinge. The flap will then be peeled back, and the underlying corneal tissue will be remoulded with another laser (excimer). Once the cornea is reshaped appropriately, the cornea flap will be flipped back into place where it will heal normally without the need for stitches. The entire procedure takes less than 20 minuets.

What will I experience following LASIK?

Following the surgery, you can expect some irritation as your eyes will be dry. You will be given medicines and eye drops to keep your eyes moist and to prevent pain and infection. Your ophthalmologist may advise you to use a patch over your eyes at night until they heal. You may have problems with vision for the first day after the procedure, but healing occurs fairly rapidly, and your vision should improve within a few days.

You will need to follow up with your ophthalmologist on the next day after the procedure, and keep regular follow up appointments periodically during the first six months. During your recovery period, you will have to avoid strenuous activities, contact sports, and swimming for a few weeks.

What are the risks of LASIK?

As with any surgery, LASIK carries its own set of risks which include:

  • Under correction: You will not experience clear vision if the procedure removes too little tissue from your eyes. Under correction can be corrected by repeating the procedure when your refraction is stable.
  • Overcorrection: Overcorrection can be more difficult to rectify than under correction, as more than the required amount of tissue is removed.
  • Dry eyes: Temporary decrease in tear production can be expected after LASIK for up to six months. Sometimes, these symptoms may persist or worsen if you have pre-existing Dry Eye Syndrome.
  • Vision abnormalities: You may experience glares, halo, or double vision temporarily for a few days after LASIK. You may require additional treatment if they worsen.
  • Conditions such as rheumatoid arthritis, immunodeficiency, pregnancy, dry eye syndrome, unstable refraction, and abnormal shape of the cornea can increase the risks associated with LASIK.
  • Very rarely, progressive corneal thinning (melting) and irregular transformation (ectasia) may occur.

Your ophthalmologist should be able to address all your concerns before you consider LASIK.

What are the advantages of LASIK?

LASIK is preferred over PRK due to the following benefits

  • Your vision may be corrected almost immediately
  • You will have less pain after surgery
  • You won't require adhesive dressings (no stitches or bandages)
  • It is a well-established technique with excellent safety profile.

Your dependence on eyeglasses and contact lenses may be reduced. Most patients no longer require any visual aids after LASIK.

PRK (Photorefractive Keratectomy)

Photorefractive keratectomy is another refractive surgical procedure, which uses laser to correct the shape of the cornea, so that it focuses an image more accurately on the retina. PRK can be used to treat low to moderate levels of nearsightedness, farsightedness and astigmatism. Your vision is corrected by the removal of a thin layer of tissue from the surface of the cornea and reshaping the cornea.

What are the best candidates for PRK?

This procedure is typically used where opportunities for flap creation are less than ideal, for examples the corneas may be too thin, pupils are too large, or prescription is too high to safely create a flap. PRK involves polishing away the outer layer of the cornea (epithelium) before applying the laser, therefore corneal tissue is saved by not creating a flap with PRK. This could be an advantage for people who enjoy contact sports (such as boxing, martial arts). These people have a greater risk of getting hit in the eye which may cause flap movement.

What are the preoperative preparations?

If you use contact lenses, you may be asked to stop wearing them for a period of time prior to the procedure.

How is PRK performed?

In PRK, the entire outer layer of cells (epithelium) is removed and an excimer laser is applied to remove the correct amount of tissue beneath from the cornea. Your eye subsequently regrows the surface layer, but requires the patient to wear a soft contact lens for 3 to 5 days, until the healing process is completed.

This procedure is performed under local anaesthesia and it takes shorter time than LASIK to treat both eyes.

What will I experience following PRK?

You may experience some eye irritation and sensitivity to light for 2-3 days which is normal. Your doctor will prescribe eye drops to control pain, inflammation and infection. Vision may be blurry initially, but improves gradually over a period of weeks to months.

What are the risks associated with PRK?

This treatment was the original laser vision correction procedure and it has been proven to be very safe and accurate. However, potential complications include under/over correction, infection, pain, reduced vision, corneal haze, glare and halo. Very rarely, progressive corneal thinning (melting) and irregular transformation (ectasia) may occur.

Your ophthalmologist should be able to explain the individual risks and possible side effects to you and decide whether this treatment is the right option for you.

SMILE (Small Incision Lenticule Extraction)

Small Incision Lenticule Extraction (SMILE) is a relatively new laser refractive surgery, which has been used to treat people who are nearsighted (myopia) and astigmatism. The procedure involves the use a special laser to reshape the cornea permanently by removing a small amount of the eye tissue internally through a key-hole incision.

What are the best candidates for SMILE?

At present, this procedure is predominantly indicated for the correction of myopia or myopic astigmatism of up to -10.00 D spherical equivalent or -5.00 D of astigmatism. It still has not been established in correcting hyperopia (farsightedness), but further research and clinical studies are being undertaken currently.

How is SMILE performed?

The procedure is performed under topical anaesthesia (eye drops) and an oral medication can be given for optimal relaxation. It involves the use a specially licensed laser to create the outline of a round-shaped disc within the cornea together with a very small tunnel that links this outline to the surface. Your ophthalmologist is then able to manually remove this round–shaped piece of tissue through the tunnel. The procedure is usually completed in less half an hour.

What will I experience following SMILE?

Similar to LASIK, you may experience some eye irritation and sensitivity to light for 2-3 days which is normal. Your doctor will prescribe eye drops to control pain, inflammation and infection. The healing process for each individual is different, visual acuity is usually good 1-2 days after the procedure, and becomes stable within 2-3 weeks.

What are the risks associated with SMILE?

Like all surgical procedures, SMILE is not without side effects. Potential risks include under/overcorrection, infection and inflammation. Very rarely, progressive corneal thinning (melting) and irregular transformation (ectasia) may occur.

Your ophthalmologist should be able to explain the individual risks and possible side effects to you and decide whether this treatment is the right option for you.

What are the advantages of SMILE?

There are several theoretical advantages of SMILE:

  • No flap-related complications
  • Lesser chance of post-operative Dry Eyes
  • More biomechanical stability and lower risk of ectasia
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