PRK Surgery
PRK surgery (photorefractive keratectomy) is a computer-assisted surgeon-controlled laser eye surgery that treats myopia (nearsightedness), hyperopia (far sightedness) and astigmatism by removing the surface layer of the cornea (the clear covering of the front of the eye) and reshaping the underlying tissue with excimer lasers (cool, concentrated beams of ultraviolet light). The procedure is performed with the VISX Star S4™ Laser System, takes about five to ten minutes per eye depending on the type and amount of correction required, and is performed on an outpatient basis at Horizon Laser Vision Center. The surgeon determines the amount of the treatment (vision correction) required with the help of WaveScan® technology and programs the patient's unique corneal shape refractive error (glasses prescription) into the computer prior to your procedure.
PRK surgery differs from LASIK in that a corneal flap is not created before the laser is used to treat the cornea - the cornea is sculpted rather than cut. The PRK process uses an excimer laser to sculpt an area 6.0 to 6.5 millimeters in diameter on the surface of the cornea. As can be seen from the diagram, this process removes approximately 5-10% of the thickness of the cornea for mild to moderate myopia and up to 30% for extreme myopia - about the thickness of 1 to 3 human hairs.
The major benefit of this procedure is that the integrity and the strength of the cornea are retained. The excimer laser is set at a wavelength of 193nm, which can remove a microscopic layer of cells without damaging adjoining cells or tissue. This allows the surgeon to make extremely accurate and specific modifications to the corneal surface to correct refractive errors.
Immediately preceding the procedure, numbing drops are placed in the eye and the area around the eye is cleansed. A small instrument called a lid speculum holds the eyelids open to prevent blinking and you will be asked to focus on a flashing fixation or target light in the laser.
PRK surgery is performed in two main stages. During the first stage the surgeon looks through the laser's microscope and vaporize the very superficial tissue (epithelium) from the front of the cornea leaving an incredibly smooth undamaged tissue surface. This tissue regenerates and will grow back in a few days. Once the tissue, usually less than 50 microns (1mm = 1000 microns), is removed, the surgeon will smooth the underlying surface and eliminate any moisture. You will not experience any discomfort during this procedure, however you will notice your vision becomes more blurred. The surgeon will then be ready to treat the underlying tissue and modify your prescription.
While looking through the microscope during the second stage the surgeon will use the excimer laser to reshape the cornea by vaporizing an ultra-thin amount of the exposed corneal tissue. Once the treatment is complete antibiotic and anti-inflammatory drops are placed in the eye and a bandage contact lens is inserted. The contact lens will protect the cornea and help the epithelium to heal more rapidly. The contact lens will also help decrease discomfort during the recovery period.
