Laser-Assisted in Situ Keratomileusis (LASIK) refers to a type of refractive surgery for correcting hyperopia, myopia and astigmatism. An ophthalmologist performs the surgery and reshapes the cornea for improving visual acuity. The ophthalmologist uses a specialised laser, referred to as excimer laser, to treat refractive errors, improve vision and eliminate the need to use either contact lenses or glasses.
LASIK Eye Surgery Procedure
In the LASIK eye surgery procedure, a thin flap is created on the eye using an instrument by name microkeratome and it is folded so the tissue below it can be remodelled with the help of a laser. The flap is then repositioned. In the case of people having myopia, the too-steep cornea is flattened out and in the case of those having hyperopia, the cornea is made steeper. Excimer laser also corrects astigmatism by smoothing the irregular cornea into its near normal shape.
Preoperative procedure
Patients who wear soft contact lenses are advised not to wear them five to twenty-one days prior to the surgery. On the other hand, patients who wear hard contacts are required to stop wearing them for a minimum period of six weeks and additional six weeks for every three year blocks they have been used.
LASIK is carried out on patients who are aged 18 and above if their eye prescriptions have been stable during at least one year before the surgery. The patients' pupils may be dilated and examined. The eyes are also subjected to examination using pachymeter to determine the thickness of the corneas and topographer to measure the corneal surface contour. Astigmatism and other irregularities in cornea's shape are also detected. Based on this information, the amount of corneal tissue and the area from where it is to be removed is determined by the surgeon.
The new wavefront technology which involves sending light waves through the eye provides a more precise map of the aberrations affecting a patient's vision. The surgeon may also seek information on the health problems that patients may have and medications that they are already taking. Sometimes the doctor may prescribe an antibiotic to reduce the risk of contracting an infection after the surgery. At other times, the patient may be offered an oral sedative that is short acting as a pre-medication. Eye drops that act as anaesthetics often instilled before the procedure.
Operative procedure
The first step is the application of the corneal suction ring to hold the eye steady. After immobilizing the eye, the flap with a hinge is created using a femtosecond laser or a mechanical microkeratome that has a metal blade. The flap is then folded back to reveal the middle part of the cornea called stroma.
In the second step, a 193 nm excimer laser is used for remodelling the corneal stroma. The tissues are vaporised in a controlled manner using the laser and tens of micrometers thick tissues are removed. When laser ablation is performed in the deeper corneal stroma, patient experiences rapid visual recovery and lesser pain. The eye tracking system of the excimer laser follows the eye position of the patient about 4,000 times in a second to direct laser pulses precisely within the treatment zone.
The final step is the flap repositioning. The flap remains in position because of natural adhesion till it is healed.
Postoperative care
A course of antibiotic as well as anti-inflammatory eye drops are prescribed after the surgery. Patients are advised to take rest and use dark glasses to protect their eyes from bright light. They are also required to moisturise their eyes with tears that are free from preservatives.
