In LASIK (Laser-Assisted In Situ Keratomileusis), a flap is created and the laser reshaping is then performed below the flap. Laser treatment to treat near-sightedness, far-sightedness and astigmatism, is not benign. All of the available treatments for this condition have the potential to dramatically improve vision at distance. Worldwide, there is a 95% satisfaction rate with these treatments. But considering that the treatment is being performed on healthy eyes, the 5% of patients who are dissatisfied is a high number. And most alarming, most of these people have excellent visual acuity as measured by an eye chart.
You Can't Have It All
In young people between age 21 and 40 who still maintain their ability to see up close, even while wearing their eyeglasses or contact lenses, Laser Vision Correction can improve distance vision without adversely affecting near vision. But beginning at age 40, and continuing until age 70, there is progressive hardening of the natural lens inside the eye. This makes the lens less capable of changing shape during focusing, resulting in decreased ability to read with increasing age. This process is known as presbyopia, and Benjamin Franklin invented bifocals in 1760 to cope with this condition.
Nearsighted or myopic people who take off their glasses to read also develop presbyopia. But the symptoms are hidden from them until they wear their contact lenses or distance eyeglasses. This is because their natural focal point is close to the eye and they don't require their focusing muscles to work to make this distance clear to them. Unfortunately, nearsighted people often poorly understand the consequences of LASIK, believing that they will obtain distance vision while having little effect on their near vision.
Because Laser Vision Correction is primarily designed to correct distance vision, in nearsighted people, there is a tradeoff between gaining distance vision and losing near vision, especially after age 40. In essence, Laser Vision Correction makes the nearsighted person a "normal sighted" person. And since normal sighted (emmetropic) people require reading glasses or bifocals beginning around age 40-45, the same will be true for myopic people after Laser Vision Correction.
The use of contact lenses to the prospective myope to demonstrate what his or her vision will be like following laser vision correction is a very good idea if the doctor is not convinced that the patient understands this future handicap. The loss of the ability to read in bed or see near vision details, such as text on a cellular phone without the aid of reading glasses, can be upsetting for people who have enjoyed this capability for many years. Being able to see the television, but not the remote control, is a frequent frustration of presbyopia. Some doctors will purposely under-correct one of the eyes with laser, leaving the eye slightly nearsighted so that some near and intermediate vision is possible without the use of glasses. This is called "monovision." However, monovision is not always well tolerated, and even in patients who do tolerate it, there is a tradeoff in distance clarity compared with having both eyes corrected for distance vision.
Patients who are treated using a monovision technique have to be exquisitely careful when driving a car to make sure that the rear view mirrors are aligned with the distance corrected eye. And patients who are symptomatically blurry with monovision, but who don't want to give up the ability to read without glasses, should wear eyeglasses when driving, with a clear lens in front of the distance corrected eye and a prescription lens in front of the near corrected eye.
Different Types of Laser Vision Correction
LASIK
LASIK, or laser in-situ keratomilieusis, is a two-step procedure in which a sliver of the cornea is angled backward while the laser is applied underneath. The thin sliver of cornea is then placed back onto the surface. Intralase uses laser light to perform the first step in LASIK - the creation of a corneal flap. A microkeratome uses an oscillating steel blade to create the corneal flap. The sliver of cornea can be created using a metal oscillating blade (microkeratome) or a separate laser known as Intralase. The latter is, in my opinion, more precise and creates a better-fitting flap.
The actual laser reshaping of the cornea underneath the flap is performed with an Excimer laser using a computer controlled ultraviolet beam of light that reshapes the cornea, or outer window of the eye, in an effort to allow light to focus more directly on the retina. The Excimer has been used since the early 1980's and underwent numerous clinical trials since that time to refine its use and determine its safety and effectiveness. Now in its fourth decade of use, the Excimer laser is routinely used to treat nearsightedness, farsightedness and astigmatism. Each pulse of the laser disrupts the molecular bonds between the corneal cells with accuracy up to 0.00004 of an inch, which makes it extremely accurate. Often, tissue measuring about 1/2 the thickness of a human hair is removed to achieve the proper amount of correction. The Excimer laser produces a cool or non-thermal light beam. This makes it ideal for corneal surgery because it eliminates the possibility of thermal damage to surrounding tissue. Its accuracy provides surgeons with a tool that can deliver highly predictable results.
Epi-LASIK
Epi-LASIK is similar to LASIK, but creates a much thinner flap of tissue compared with LASIK. The recovery from this procedure is similar to PRK, listed below.
PRK
In PRK (photorefractive keratectomy), the Excimer layer is used exclusively to reshape the cornea. To accomplish this, the surface layer of the cornea, known as epithelium, is also removed. Although the PRK procedure itself is painless, patients may experience blurry or hazy vision for one to five days afterward and variable discomfort until the epithelium heals and covers the treated area. Final visual results may be realized anywhere from several days to a month or more. Anti-inflammatory eyedrops are taken for one to three months. Like LASIK, PRK is often used to treat low to moderate amounts of nearsightedness, farsightedness and astigmatism, but because it spares more cornea tissue that LASIK, it is often used to treat higher refractive errors as well.
Summary
Laser vision correction is a fabulous procedure for a large majority of patients. And even in those patients in whom the outcome is less than perfect, the advantages of not having to deal with strong glasses and uncomfortable contact lenses can be dramatic. Glare, a frequent published side effect of laser vision correction, is less pronounced than in previous years with the advent of custom computer algorithms. But glare is a universal occurrence in all natural optical systems. Patients who wear strong glasses or contact lenses have glare. And glare exists, to some extent, in all patients who undergo laser vision correction, even when it is perfectly performed. It is not necessarily true that the highest volume LASIK surgeons have the best results. In fact, in many of these practices, there is a lack of contact with the surgeon both before and after the procedure. Measurements are often performed by ancillary staff, and the post-operative care often does not involve a physician. Because laser vision correction is largely an automated procedure, it is recommended that you seek the care of a physician who is actively involved in the pre and post-operative care.
