What is LASIK
LASIK is short for 'Laser-Assisted in Sate Keratomileusis'. It is a type of refractive laser eye surgery carried out by eye surgeons for correcting myopia, hyperopia, and astigmatism. LASIK surgery replaces corrective eyeglasses or contact lenses. People prefer LASIK surgery to photorefractive keratectomy, PRK. Patients recover faster from lasik surgery, and there is less pain experienced. Medically though, PRK is chosen as an alternative in some cases.
Procedure
Certain preparations are required before a surgery. The operation consists of creating a thin flap on the eye, folding it to enable remodelling of the tissue underneath with laser. The position of the flap is then changed and the eye is left to heal after the completion of the surgery.
Preoperative Requirements
The soft lenses worn by the patients have to be discontinued approximately 10 to 15 days before surgery. Some doctors' advise patients wearing hard lenses to discontinue wearing them for a minimum of six weeks plus another six weeks for every three years the hard contacts had been worn. Before the surgery, the doctor with the help of a pachymeter examines the patient's corneas to determine their thickness, and with a topographer to measure their surface contour. Using low-power lasers, a topographer creates a topographic map of the cornea. This process also helps in detecting astigmatism and other irregularities in the shape of the cornea. All this helps the surgeon to work out the amount and locations of corneal tissue to be removed during the surgery. Generally the patient has to take an antibiotic before the surgery to reduce the chances of infection.
Operation
The patient is awake during the surgery, but is given a mild sedative and anaesthetic eye drops. LASIK is carried out in two stages. The first step is to create a flap of corneal tissue. The second step is remodelling of the cornea underneath the flap with laser. The flap is then repositioned.
Flap creation
To hold the eye in place a corneal suction ring is applied to the eye. This can sometimes cause small blood vessels to burst, resulting in bleeding or subconjunctival hemorrhage into the white (sclera) of the eye. But this is no cause to worry as it resolves within several weeks. Increased suction often causes a brief dimming of vision in the treated eye. Once the eye is immobilized, the flap is created. This process is achieved with a mechanical microkeratome using a metal blade, or a femtosecond laser microkeratome (procedure known as IntraLASIK) that creates a series of tiny closely arranged bubbles within the cornea. A hinge is left at one end of this flap. The flap is folded back, revealing the stroma, the middle section of the cornea. The process of lifting and folding back the flap can sometimes cause discomfort.
Resources: LASIK in Germany
Laser remodelling
The second step of the procedure is to use an excimer laser (193 nm) to remodel the corneal stroma. The laser vaporizes tissue in a finely controlled manner without harming the adjacent stroma. There is no burning or cutting to ablate the tissue. The layers of tissue removed are tens of micrometers thick. The laser ablation in the deeper corneal stroma helps in speedy visual recovery and there is very little pain. The vision becomes a little hazy once the flap is lifted.
Reposition of flap
After the stromal layer has been reshaped by LASIK, the surgeon carefully repositions the flap over the operated area and checks for the presence of air bubbles, debris, and proper fit on the eye. The flap remains in position by natural adhesion until healing is completed.
Postoperative Care
Patients have to take a course of antibiotic and put anti-inflammatory eye drops after the surgery. These are discontinued after a few weeks. Patients have to wear darkened glasses to protect their eyes from bright lights and protective shields to prevent rubbing of the eyes during sleep.