Differences Between Procedures
In the late 1970's doctors all around the world began treating nearsightedness and astigmatism with incisional refractive surgery (commonly known as RK - Radial Keratotomy). This procedure allowed close to a million people to experience a lifestyle that was less dependent on glasses or contact lenses. Radial Keratotomy and similar procedures achieved great success in the hands of skilled surgeons. However, enhancements were common and often patients experienced significant side effects due to the numerous incisions that were made. Refractive surgery entered a new era with the advent of the excimer laser. The excimer laser is a computer controlled ultraviolet beam of light that has the ability to remove microscopic amounts of corneal tissue. This removal of the tissue, or reshaping of the cornea, can reduce or eliminate common causes of distance vision problems such as nearsightedness, farsightedness, and astigmatism. The excimer laser was invented in the early 1980's and has undergone numerous clinical trials since that time, culminating with its approval by the Food and Drug Administration (FDA) in October 1995. The excimer laser produces a "cool" or non-thermal light beam as most of its heat is dissipated into the air. This makes it ideal for corneal surgery, because the laser is able to remove microscopic amounts of tissue with minimal effect to surrounding or underlying tissue. There are two different procedures that utilize the excimer laser; Laser Assisted In-Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK).
Side Effects
Following LASIK, patients may experience certain temporary side effects, including irritation, tearing, and light sensitivity. Generally these side effects are temporary in nature, and dissipate within 1 week to 6 months. We routinely send out surveys to LASIK patients concerning post-operative side effects. Below you will find a chart which displays some of the side effects which have been experienced by our patients:
Definition of Terms
Below, please find a glossary of terms that will enhance your understanding of the eye and assist you in making important decisions about your eyesight.
Astigmatism
Regular astigmatism occurs when light rays are focused at more than one point on the retina and results from uneven curvature of the cornea or lens.
Cornea
The cornea is, in a sense, the "eye's window" that provides most of the focusing power when light enters the eye. It is the outermost layer of the eye; if you were to touch your eye, the cornea would be the first thing your finger would feel. The cornea itself is composed of five layers, with the epithelium forming the outermost layer.
Excimer
The excimer laser is an argon-fluoride gas laser that emits computer-controlled pulses of cool (non-thermal) ultraviolet light. These rays of light sculpt the cornea. Each pulse of the laser is capable of removing 1/40 of a human cell. It is this precision that maintains the integrity of the eye after vision correction procedures.
Hyperopia
Hyperopia is commonly known as farsightedness. It occurs when light rays are not bent enough to focus on the retina. Hyperopia is commonly a consequence of the cornea being too flat.
Iris
The iris is the colored part of the eye. Its central perforation is the pupil. Contraction or expansion of the muscles of the iris cause the pupil to constrict or dilate.
LASIK (Laser in Situ Keratomileusis)
LASIK is a painless, outpatient procedure that treats refractive errors by removing corneal tissue. A protective corneal flap is made and folded back to reveal the underlying tissue. Computer-controlled pulses of cool laser light are applied to the inner layers of the cornea in an attempt to reshape the cornea. The flap is then placed back in its original position and allowed to heal naturally.
Lens
The lens is a transparent structure located behind the iris. By altering its shape, the lens provides fine-tuning for focusing and reading. Between the ages of 40 and 50, the lens becomes more rigid, causing presbyopia. Beyond age 60, the lens hardens and becomes cloudy. Cataracts may form and interfere with vision.
Microkeratome
A microkeratome is an instrument used during the LASIK procedure that creates a flap out of the surface layer of the cornea, thus exposing the underlying corneal layer that will be reshaped by the laser.
Micron
A micron is a unit of measurement that is equal to one millionth of a meter.
Myopia
Myopia is typically referred to as nearsightedness. It occurs when light rays are focused in front of the retina instead of directly on the retina. Myopia generally arises when the cornea is too steeply curved.
Presbyopia
Presbyopia usually develops between the ages of 40 and 50. As the lens ages, it becomes increasingly more rigid and it loses its refractive integrity. As a result, a need for reading glasses develops.
PRK (Photo-Refractive Keratectomy)
PRK is a painless, outpatient procedure that treats refractive errors by removing corneal tissue. Computer-controlled pulses of cool laser light are applied to the surface of the cornea to reshape its curvature. Since the epithelial layer of the cornea is removed during this procedure, healing is aided with the use of a bandage contact lens, which is used for approximately 3 days.
Pupil
The pupil is the black opening in the center of your eye. It controls the amount of light that enters your eye. When you are in a bright environment, the pupil becomes smaller, to decrease the amount of light that passes through. Conversely, in the dark, the pupil expands to allow more light to reach the back of the eye.
Refraction
Refraction is the deflection of a ray of light when it passes from one medium into another medium with a different optical density. Laser vision correction improves the eye's natural refractive properties.
Retina
The retina lines the inside wall of the eye and consists of fine sensory tissue. It acts like the film in a camera that captures and transmits images.
RK (Radial Keratotemy)
RK is a procedure that corrects myopia by making multiple corneal incisions in a radial pattern. This relieves pressure and flattens the cornea, increasing visual acuity.