How Modern Laser Vision Correction Works

LASIK Or Laser-Assisted In-Situ Keratomileusis

LASIK is also known as the “cut, flap, and zap” method. Here are the three main parts to the LASIK procedure:

  • 1. CUTTING THE FLAP
    The cornea is cut to create a tissue flap using either the microkeratome blade or the femto-second laser. The latter is often touted as a “bladeless” procedure giving the impression to the un-informed that no cut is made in the cornea. However, in reality, “bladeless” here does not mean “cut-less”.
  • 2. LIFTING THE FLAP
    The cornea flap is lifted up to expose the cut cornea tissue bed and the excimer laser is positioned over the eye. The patient is required to fixate his/her gaze on a red blinking light.
  • 3. THE “ZAP” AND FLAP CLOSURE
    The “zap” is the actual laser vision correction step. Here, the excimer laser is used to precisely reshape the cornea curvature to correct the refractive power. The actual laser time is usually less than 20 seconds.
  • Upon completion of the laser treatment, the flap is repositioned back to protect the treated surface. The flap adheres with only tissue pressure and is prone to wrinkles and dislodgment during the first few days if subjected to trauma.
  • In general, the entire LASIK procedure is over in about 10 to 20 minutes per eye. LASIK is known for its quick visual recovery and low complication rates. It is still the de facto standard by which other vision corrective techniques are measured against. However, low complication rates does not equal to no complications. There are flap
    related complications that we should be aware of. These complications often include flap wrinkles (striaes) and flap inflammations (“Sands of Sahara”). This will result in blurriness and discomfort.
  • As cornea nerves are cut and damaged during the creation of the cornea flap, this can result in long term and even permanent dry eye. To put it in perspective, this does not happen very often, but when it does happen, it can be very distressing for the patient concerned and it is difficult to predict when this will happen.
A severe complication is flap dislodgement or complete dislocation due to trauma. If this happens, you will need to undergo an op immediately to prevent permanent and irreversible loss of best corrected vision.

ICL: Implantable Collamer Lens

  • The procedure involves implanting the ICL itself – a permanent intra- ocular contact lens – deep behind your cornea in the space between your iris and natural lens of the eye. It is considered the most invasive of all the procedures as it is done inside the eye, instead of on the cornea surface.
  • Before the ICL Procedure
    One to two weeks before the ICL surgery, the surgeon will perform a YAG laser iridotomy. After applying numbing eye drops, the eye doctor will use the Argon and YAG laser to make one or two small openings near the edge of your iris, which is the colored part of the eye.
    These openings serve as outlets that will allow the fluid in your eye to circulate around the lens later, as a precaution against the risk of angle closure glaucoma. The surgeon will also prescribe eye drops for you to use during the weeks leading up to the ICL procedure. During this time, your corrective lens will also be selected based on your individual prescription.
  • 1. The procedure can be done under numbing eye drops only or in conjunction with general anesthesia depending on patient’s and surgeon’s preference. A small incision is made at the side of the cornea and a clear jelly-like substance is injected into the eye to create the space to insert the lens and protect the inner surfaces of the eye during the lens placement.
  • 2. Next, the ICL is inserted. The lens will be folded and loaded into a small cartridge device that will be placed through the incision.
  • 3. As the lens is inserted, it will gently unfold within your eye.
  • 4. Once the lens has fully unfolded, the four corners of the lens will be tucked behind your iris. This makes the lens invisible to both you and others.

ReLEx SMILE: Refractive Lenticule Extraction, Small Incision Lenticule Extraction

The ReLEx SMILE procedure is the most recent technology in laser vision correction. Instead of vaporising the cornea tissue, a femto- second laser is used to cut out a lens-shaped piece of corneal tissue to correct myopia.

  • The laser precisely creates a refractive lenticule (a thin lens- shaped cornea tissue) within the cornea layers. A small 4mm incision is made on the cornea surface.
  • The refractive lenticule is removed through the small incision.
  • The removal of the refractive lenticule changes the way light bends into the eye, allowing you to see clearly. The micro incision self-heals.
  • In general, this procedure takes about 10 to 15 mins per eye i.e. faster than LASIK as only one laser is used throughout. Since it is a flapless, bladeless procedure, there is no worries about flap-related complications that are the most common cause of LASIK complications.
    However, one important downside of ReLEx SMILE is that no enhancements are possible! The procedure can only be done once.
    If there is a need to make further corrections or enhancements, ReLEx patients will have to turn to ASA (Advanced Surface Ablation) procedures such as Advanced PRK, LASEK or epi-LASIK to do their enhancement surgeries.

    Cornea incision size

  • ReLEx-SMILE 4mm or less
  • LASIK approx 20mm


  • This technology shows great promise as it does away with the need for patient’s co-operation to fixate his gaze steadily throughout the laser treatment. This important but often overlooked fact is a major cause of poor result from laser vision correction. Also, environment variables such as humidity and chemical vapours do not affect the accuracy of the laser. However, being a newly introduced procedure, the track record of long term complications, patient numbers and long term success rates remains to be determined.

Advanced Surface Ablation (ASA) Includes Epi-LASIK, LASEK, Advance PRK

Advanced Surface Ablation (ASA) techniques evolved as a result of eye doctors searching for ways to minimize or avoid the pitfalls of LASIK such as flap complications, cornea thinning issues from the cut flap, dry eyes and flap trauma. It was discovered that with the advantages of modern lasers and medications and the wearing of a bandage contact lens for four to five days post op, these LASIK pitfalls can be avoided by simply going back to where laser vision correction was first performed, that is on the surface of the cornea! Of the three surface techniques, advanced PRK, LASEK and epi-LASIK; the latter is the most recently evolved technique.

epi-LASIK: HOW IT IS DONE

  • First, a suction ring is placed over the eye to steady it.
  • A tissue separator moves gently across the cornea surface to shake off superficial epithelium cells.
  • The epithelium layer is now gently removed.
  • A tissue separator moves gently across the cornea surface to shake off superficial epithelium cells.
  • The excimer laser is applied to reshape the cornea curvature.
  • A transparent, high-oxygen content soft contact lens is then placed over the cornea to act as an artificial cornea flap to protect the treated surface while the epithelium cells regenerate.
  • The epithelium cells then take 3-5 days to to heal and regenerate. It is very important to use the eye drops medications prescribed and stay away from strong sunlight for good healing. The high- oxygen permeability contact lens is removed after 5 days.