Laser Vision Correction (LASIK/PRK)

Not everyone has perfect vision. Some suffer from myopia (also known as near-sightedness), some are hyperopic (farsighted) and there are some who have astigmatism (a condition where objects both near and far can appear to be blurred or distorted). All these problems are due to the way the cornea (the clear dome at the front of the eye) or the eyeball itself is shaped. One of the best medical breakthroughs in the eye-care field was the introduction of laser vision correction.

A few years back if you had one of the above vision problems, a visit to your local eye doctor would result in you getting either spectacles or contact lenses; there wasn’t much else to offer. But today, your options are wider. There are several laser vision corrections available, as well as some non-laser correction methods. It is extremely important that you are aware of all these options. You don’t need to go far to gather information. Your hometown eye doctor will be able to educate you on these options so that you can make a good decision as to which procedure you should undergo.

History of Laser Correction

The very first laser vision correction procedure was photorefractive keratectomy or PRK. PRK is normally used in correcting mild to moderate range of both near and far sightedness as well as astigmatism. In the PRK procedure an eximer laser is used to carve around 5 – 9 millimeters in diameter on the eye surface. Only one eye is treated at a time since it takes anytime between a few days to a few weeks to regain full vision. The drawback with the PRK procedure is that the patient almost always feels uncomfortable until the entire cornea heals. This can be very disturbing and irritating for the patient especially if it takes weeks to heal!

A while after PRK was pioneered, another procedure called LASIK was introduced. LASIK (or “Laser Assisted In Situ Keratomileusis”) was undoubtedly the most profound development to make refractive surgery a everyday reality. It is a fairly simple and fast procedure that takes only a few minutes. However if you are contemplating LASIK, it is best for you to first check your eyes with an experienced optometrist or ophthalmologist before proceeding to your local surgery center. Once you have all the basic information regarding your eyes, you can make the most informed choice about the best procedure for your situation.

LASIK is an extremely popular procedure because it does not cause much discomfort, it is virtually pain-free, the time spent “under the knife” is just a few minutes and, most importantly, it takes just a few days to recover. In fact, typically with LASIK you regain your clear sight almost immediately after surgery! In this procedure, the patient is given local anesthesia (eye drops) and operated on using an automated microkeratome (metal blade) that creates a flap on the cornea which is then ablated using the eximer laser. In the simplest terms, the cornea is reshaped to adjust the way the light focuses in the eye and onto the retina in order to have a clear vision.

A successful LASIK operation can give you 20/20 vision and in some cases a 20/15+ vision is achieved. That’s very impressive! However LASIK surgery may not last forever; nothing can stop nature from taking its course. As you grow older, especially when you hit age 40, there will be a high likelihood that you will need reading glasses or bifocals. If you are in your 40’s or getting close, discuss with your hometown eyedoctor how you can possibly avoid using reading glasses. One of the most popular methods is a technique called “monovision,” where one eye is used for near vision and the other for distance.

Another version of LASIK surgery that you might want to consider is the “Custom LASIK” surgery (also known as Wavefront LASIK), which uses a 3-dimensional measurement to study how your eye processes images so that the laser can be guided to reshape the cornea. With the new wavefront measurement system, very precise and exclusive vision correction can be achieved. This is something that the conventional LASIK cannot achieve.

The LASEK procedure is another laser vision correction procedure that many have not heard of. LASEK is similar with LASIK except for a few differences. In LASEK, the outer layer of the cornea is cut using a very fine blade called a trephine instead of a microkeratome, before the eximer laser is used. If at all your eye doctor recommends LASEK instead of LASIK, make sure you find out why that the former is being recommended to you since this procedure is not meant for everyone.

A new technology called IntraLase offers an alternative to standard LASIK by replacing the metal microkeratome with a laser cut. This “blade-free” procedure is also known as ‘all laser LASIK’. In this procedure, computer aided software is used to guide the IntraLase laser beam inside the middle layer of the cornea to make the flap. The outcome of this procedure is similar with LASIK.

There is another laser procedure currently under investigation called photoablative inlays (PAI) or PAI – LASIK. This procedure is being developed by optics giant Bausch & Lomb and is similar to LASIK. The crucial difference is that PAI-LASIK would add to the cornea rather than subtract from it. This is done by inserting a custom "photoablative inlay" lens underneath a LASIK flap in the cornea. The advantage of this procedure is that surgeons will be able to correct higher degrees of myopia and it is reversible. This procedure is not yet available as it’s still in experimental development.

Preoperative

Patients wearing soft contact lenses typically are instructed to stop wearing them approximately 7 to 10 days before surgery. One industry body recommends that patients wearing hard contact lenses should stop 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 surfaces of the patient's corneas are examined with a computer-controlled scanning device to determine their exact shape. Using low-power lasers, it creates a topographic map of the cornea. This process also detects astigmatism and other irregularities in the shape of the cornea. Using this information, the surgeon calculates the amount and locations of corneal tissue to be removed during the operation. The patient typically is prescribed an antibiotic to start taking beforehand, to minimize the risk of infection after the procedure.

Operation

The operation is performed with the patient awake and mobile; however, the patient typically is given a mild sedative (such as Valium) and anesthetic eye drops.

Lasik is performed in two steps. The initial step is to create a flap of corneal tissue. 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 be uncomfortable.

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 damaging adjacent stroma by releasing the molecular bonds that hold the cells together. No burning with heat or actual cutting is required to ablate the tissue. The layers of tissue removed are tens of micrometers thick.

During the second step, the patient's vision will become very blurry once the flap is lifted. He/she will be able to see only white light surrounding the orange light of the laser. This can be disorienting.

Currently manufactured excimer lasers use a computer system that tracks the patient's eye position up to 4,000 times per second, redirecting laser pulses for precise placement. After the laser has reshaped the cornea, the Lasik flap is repositioned over the treatment area by the surgeon. The flap remains in position by natural adhesion until healing is completed.

Performing the laser ablation in the deeper corneal stroma typically provides for more rapid visual recovery and less pain.

Questions for Your Eye Doctor

Most patients are unaware of options available with laser vision correction procedures or refractive surgeries (although LASIK has been well advertised and is gaining in popularity). However if you are planning to have laser vision correction, then you need to find out crucial information.

How would you know if you qualify for the procedure?
What is the procedure all about?
What is the expected outcome?
What are the complications that may arise?
Any risks involved?
How much will it cost and how do I know which surgeon to choose?

These are important questions that must be answered before proceeding with LASIK or any other vision correction procedures. Make sure to ask your local eye care provider about your refractions options.

For more information about LASIK see the FDA’s excellent website:

http://www.fda.gov/cdrh/lasik/

Ref: Wikipedia, the free encyclopedia