The procedure ‘LASIK’ for correction of refractive errors has now become very familiar. This laser correction of vision has changed the lives of millions for the better.
For more than a century, spectacles have provided good vision for people with almost all kinds of refractive errors. Spectacles are still the first option to start with. Many individuals have even used them in distinctly different styles and shapes and made them a part of their identity.
For those who were looking for alternatives, contact lenses provided the break, to show off their faces without spectacles.
More and more people are on the lookout for a ‘permanent’ solution for their refractive errors. LASIK is being offered as a magic cure by some commercial outfits. A lowdown on the pros and cons of this refractive surgery procedure shall help one to make an informed decision, whether to go for it or not.
Refractive surgery for vision correction has made tremendous advances since its start as radial keratotomy, or RK. The concept was first used in the early 1960s by Sato in Japan. The original procedure, however, didn’t work for most people.
RK is the earliest form of vision correction surgery. It was perfected in the 1970s by the Russian ophthalmologist Fyodorov and was first performed in the United States in 1978.
Today, several different options exist to help the majority of people who wear glasses or contact lenses reduce their dependence on their corrective lenses. In almost all cases, refractive surgery is elective and cosmetic.
Vision correction surgery can benefit people with myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (vision distortion due to variation in corneal surface in different meridians).
[Vision correction surgery will usually not benefit people with presbyopia (defective near vision). This condition affects all people older than 40-45 years. In presbyopia, the lens loses its ability to change shape and thus focus the eye for near vision. A further refinement to LASIK, called multifocal LASIK, is undergoing clinical trials and may be available very soon]
Not every person requesting laser vision correction is a candidate for the surgery. Factors, such as very high refractive errors, certain ocular diseases, and certain medical diseases, may prevent a person from being a candidate for refractive surgery.

Minimum criteria for LASIK could be:
Age 18 years or older for myopia or hyperopia
Age 21 years or older for astigmatism
Stable refraction for at least 1 year
There are three main steps to the procedure:
1) Creation of a corneal flap, using a microkeratome
2) Corneal stromal ablation, using excimer laser
3) Replacing the corneal flap

The Risks
As with any surgical procedure, complications may occur. In laser vision corrections, complications may occur during the procedure (intraoperatively) or during the healing period following the procedure (postoperatively).
Complications during the procedure mainly occur during the creation of the flap with the microkeratome. These include incomplete flaps, irregular or small flaps, buttonholes, decentered flaps, or free flaps. When these complications occur during surgery, the procedure is stopped, and the flap is put back in place. The flap is then allowed to heal for 3-6 months. After this healing period, the procedure may be repeated and the flap may be recut.
Early complications after the procedure include dislodged flaps and flap folds. Folds can be described as macrofolds and microfolds, which can cause visual distortion. Dislodged flaps and macrofolds require that the flap be lifted and repositioned, thus eliminating the folds.
Other complications include interface debris (debris between the flap and the lasered cornea), epithelial downgrowth into the flap, epithelial defects, or corneal abrasions.
Infection of the cornea (infectious keratitis) and inflammation can also occur. Infections are rare but very serious if they do occur.
Refractive complications include undercorrections or overcorrections, which may require additional laser correction (an enhancement procedure) and decentered laser ablation, which may require retreatment or the use of a hard contact lens.
Laser vision correction could also induce astigmatism. Halos and glare, especially at night, may occur after the procedure. They are common after the procedure but usually get better gradually.
Regression of the procedure may occur and would require additional laser treatment or the use of glasses or contact lenses.
After the surgery, dry eye symptoms are the most common complaint. Dry eyes following LASIK may occur due to a decrease in corneal sensation because the microkeratome cuts through the superficial corneal nerves. This may result in a decreased blink rate and, thus, a decrease in rewetting of the eye. Improvement occurs with the use of artificial tear lubrication and with time.

Every person who is considering LASIK must undergo a complete eye examination prior to surgery.
During this examination, the corneal thickness will be measured with a device called a pachymeter. Adequate corneal tissue remaining after the procedure is extremely important. If the cornea is too thin, LASIK may not be able to treat the refractive error without thinning the cornea too far, inducing a complication.
A map of the corneal surface, called topography, is performed to rule out any corneal problems that may lead to a poor result with the surgery, such as keratoconus. The size of the pupils in light and dark will be measured. People with large pupil diameters in a dimly lit room may not be good candidates for the LASIK procedure.
The refractive error will be checked prior to dilation of the pupils and again after dilation. This helps ensure that the refractive error is stable. A glaucoma test and a thorough retinal examination are also performed at this visit.
During the Procedure
The procedure is performed on an out-patient basis. It takes about 10 minutes to perform for each eye. Both eyes are usually done during the same procedure, although there may be times when the patient or the surgeon prefers to have each eye done at different times.
Prior to the procedure, most people will be given medication for relaxation. The eyes are anesthetized with topical anaesthetic drops prior to the procedure. The eyes are cleansed, and drapes are applied to the eyelids to cover the eyelashes so they cannot interfere with the procedure. The eyelids are held open with an eyelid retractor.
An instrument called a microkeratome is used to create the LASIK flap. Initially, a small mark is placed on the cornea to help realign the flap at the completion of the procedure. A suction ring is applied to the eye, which may cause a pressure sensation. The microkeratome creates a flap in the anterior cornea at about 20-25% of its depth. The flap is then retracted back, exposing the corneal stroma or inner layer of the cornea.
Next, the laser is used to resculpt the corneal surface. The laser portion of the surgery can take several seconds to several minutes to complete. During this time, the patient has to look continuosly at a target, such as a flashing red light or a flashing green light. The laser itself is invisible, although ne can hear a loud tapping sound when the laser is firing.
In myopic corrections, the laser works to flatten the central cornea. This allows light rays to focus onto the retina, reducing myopia.
In hyperopic corrections, the laser is used in the peripheral cornea, causing a steepening of the central cornea, which allows better focusing of light rays onto the cornea.
Once the laser portion of the procedure is completed, the flap is returned to its original position on the cornea. Through the natural characteristics of the cornea, the flap will seal itself in place after a few minutes. Usually, the flap is allowed to dry for approximately 3 minutes prior to removing the lid retractor. At the end of the procedure, antibiotic and anti-inflammatory drops are put into the eyes.

After the Procedure
As with any surgery, some discomfort is expected following LASIK too.
Immediately following the procedure, antibiotic drops and steroid drops will be placed into the eyes. The flap will be checked under magnification (using slit-lamp) to be sure it is smooth and wrinkle-free with no debris under it. Finally, protective eyewear, such as goggles or shields, will be placed on the eyes to protect them. With the goggles in place, one will be less likely to rub the eyes, which may cause dislocation of the flap.
The hours following the procedure can be more uncomfortable than the procedure itself.
Immediately after surgery, one may experience just a small amount of scratchiness of the eyes, or tears and burning sensation. These symptoms usually go away in about 6 hours. Your surgeon may encourage you to take a nap after the procedure. Taking a nap will help you through the most uncomfortable part of the healing with minimal discomfort.
Immediately after the surgery, most people will notice an improvement in their uncorrected visual acuity. The vision may appear rather smoky, as if one is looking through a smoke-filled room. The vision will stabilize in about 1 week.
The Good News
Almost all of the complications of LASIK are due to the complexity of the first step [unpredictable results during use of the microkeratome (the ‘blade’) and variations in surgeons’ skills].
The arrival of the Femtosecond laser has automated this step completely, without the need for a microkeratome.
The results are wonderfully better and more and more centres are beginning to offer this new procedure to their patients.
This type of LASIK is now marketed as All Laser LASIK or iLASIK (meaning intraLASIK, from a manufacturers name for femtosecond laser) or Blade-Free LASIK.
The flip side though, is the very high cost of this new technique, which is expected to come down in due course.