There are four main refractive surgical techniques currently available around the world:
Radial Keratotomy (RK, mini-RK)
These incisions are normally 90 to 95% of the thickness of the cornea and cause a reduction in the curve of the central cornea for the myopic eye. RK surgery has been found to have some limitations including fluctuation in vision and starbursts. Complications at the time of surgery, such as perforation, an irregular incision and infection are rare, but can be serious. In the USA and worldwide the use of RK in all its forms has rapidly declined.
Astigmatic Keratotomy (AK)
Astigmatic keratotomy (AK) is a treatment normally used to treat astigmatism. AK surgical incisions are made as arcs in the corneal periphery.
Photorefractivc Keratectomy (PRK)
PRK is applied to the central (optical zone) of the cornea to reduce its curvature. A modern excimer laser used for PRK sculpts an area 6.0 or more millimetres in diameter on the surface of the eye.
Vision is normally blurred for a few days after treatment. There may be a temporary apparent over correction towards hyperopia (long sight) with treatment for myopia and toward near sight for treatment of hyperopia. This is normal and later the over correction disappears in most patients.
PRK Treatment to One Eye Only
Spectacle lens wearers who undertake PRK to the first eye must be aware that there may be difficulties in vision until the second eye is treated. If for any reason the second eye is not treated there may be continuing difficulties.
Potential PRK Complications:
Mild discomfort after treatment that can be controlled by the use of analgesic (pain relieving) medications
Long Term Complications
Some haze at the treated area may occur and this may interfere with the quality of vision. It may lead to some scarring which reduces the quality of vision. The risk of haze increases with higher amounts of attempted PRK treatment. Re-treatment may have an unpredictable outcome and is usually performed by LASIK rather than further PRK.
PRK for Hyperopia (H-PRK)
Excimer laser PRK for hyperopia is less commonly performed than for myopia as the time for the corneal epithelium to heal over and stabilise after treatment is longer than for treatment of myopia. Many refractive surgeons feel that hyperopic LASIK has many advantages over hyperopic PRK, since with H-LASIK there is the same rapid healing as with myopic LASIK.
Hyperopia is treated by removing a ring of tissue from the edge of the cornea. This steepens the central cornea and has the result of bringing light into focus on the retina
Complications of H-PRK:
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Page last updated on
Saturday, 25 June 2005 12:36:31
Page last updated on Saturday, 25 June 2005 12:36:31
Highgate Ophthalmic Practice