|
|
|
|
Additional
Laser Vision Correction Surgeries
|
|||||||||||||||
_______________________________________________
Automated lamellar keratoplasty (ALK)
|
Automated lamellar keratoplasty is a procedure used to reduce high levels of myopia, usually above five to six diopters, and hyperopia. Done as an outpatient procedure under topical anesthesia, ALK usually takes less than one hour. In ALK, a thin layer of tissue is removed from the front surface of the cornea. Then, to reshape the cornea, the doctor removes tissue from the middle layer of the cornea using an instrument called a microkeratome, which functions similarly to a carpenter's plane. Finally, the top layer of tissue is replaced. ALK is usually reserved for patients with severe nearsightedness or low degrees of farsightedness. |
 |
|
In ALK for myopia, the surgeon creates a flap by slicing across the front of the cornea with an instrument called a microkeratome After folding the flap to the side, the surgeon uses the microkeratome to remove a thin disc of tissue from the exposed surface of the cornea. The front flap is then replaced without the need for sutures. By removing this layer of tissue, the central optical zone is flattened, reducing myopia. |
| In ALK for hyperopia, the surgeon slices the cornea at a deeper level with the microkeratome. The internal pressure of the eye stretches the remaining thin corneal surface, causing it to bulge forward. |
 |
_________________________________________
Astigmatic Keratotomy (AK)
 |
|
AK, treats astigmatism, as the name suggests and is used to correct mild to high amounts of regular astigmatism. To treat astigmatism, the cornea must be made spherical, like a basketball. This is done by making several incisions in the steepest part of the cornea causing it to relax and become more round. AK is similar to RK in that it is incisional surgery, but the calculated surgical incisions are made traverse to the cornea. AK may be performed in conjunction with RK. |
____________________________________________
Laser Thermokeratoplasty (LTK)
In LTK, the doctor uses a laser to heat a series of small, dot-shaped areas of the cornea. This causes the corneal tissue to expand and the curvature of the cornea steepens. LTK is used to treat people suffering from hyperopia (farsightedness). Candidates for LTK should be at least 40 years old, have stable vision and no abnormalities of the cornea or external eye.
Some 30% of the patients treated with LTK have retained functional near vision in the correction of presbyopia as well. The procedure takes approximately 2.8 seconds per eye and the effect is immediate. Recent FDA monitored studies have indicated an 84% success rate in restoring 20/40 or better vision in hyperopic patients. To date, no complications or adverse events have been reported. One hundred percent of the patients treated to date have met the FDA criteria for stability. Sunrise Technologies has recently received FDA clearance to treat both eyes on the same day. Sunrise has also begun a study of hyperopia treatment of up to 4 diopters as well as patients who are overcorrected from myopic PRK procedures.
________________________________________________
Radiofrequency Keratoplasty (RFK)
Radiofrequency Keratoplasty (RFK) uses a thin probe inserted into the superficial cornea to deliver high frequency radio waves that are used to reshape the cornea. This technique is useful for reducing and/or eliminating farsightedness. RFK is an investigational procedure.
________________________________________________
Hexagonal Keratotomy (HK)
Hexagonal Keratotomy (HK) is a surgical incisional technique used to correct low (+1.00 to +3.00) degrees of hyperopia. This procedure creates a central steepening of the cornea by making six incisions in a circumferential pattern. Current techniques avoid connecting the six incisions. One variant technique uses a second set of six transverse incisions outside the apexes of the original set (hexagonal . T). HK results have been very inconsistent and the procedure has been abandoned in the United States.
________________________________________________
Keratomileusis (KM)
Keratomileusis (KM) is a term derived by Jose Barraquer from the Greek words meaning "carving or chiseling the cornea". This term was first applied to Barraquer's cryolathe techniques used back in the 1960's. Since then, it has become more of a generic term to indicate all of the lamellar refractive corneal surgical procedures that remove a portion of the patient's corneal stroma to correct for refractive error. KM involves a variety of surgical techniques to correct refractive errors in the range of -5.00 D to -20.00 D and +4.00 D to +10.00 D.
________________________________________________
Limbal Relaxing Incision
Limbal Relaxing Incision (LRI) is a procedure used to correct mild (-1.00 to + 2.00) astigmatism. This procedure produces less glare and less discomfort than AK. The incisions heal faster and optical quality of the cornea is preserved by making incisions at the limbus. The procedure is more forgiving and easy to incorporate with cataract extraction.
For more information about other types of vision correction procedures, visit AllAboutVision.com.
__________________________________________
Copyright © 2000 LaserSurgeryForEyes.com
All Rights Reserved.
Direct any questions regarding Terms of Use or the Disclaimer
to webmaster@LaserSurgeryForEyes.com
