Astigmatic Keratotomy (AK): Astigmatic keratotomy (AK) is similar to RK, but its purpose is to correct only astigmatism. Usually, one or two incisions are made in the peripheral cornea to make it more round (as if loosening the laces on a football). This procedure is often combined with RK and has a similar long track record.AK is a reasonable procedure for correcting pure astigmatism (patients without coexisting nearsightedness or farsightedness) with results that are almost as good as those with LASIK and PRK. AK can also be used to enhance the results of LASIK and PRK by correcting small residual amounts of astigmatism. The most frequent use of AK today is to correct astigmatism at the time of lens implant surgery (either cataract or clear lens extraction surgery).
Cataract Surgery: For patients with significant cataracts who are looking to correct their nearsightedness or farsightedness, cataract surgery presents the best option. After removing the cataract with ultra-sonic power, the surgeon can implant a lens that will reduce or eliminate nearsightedness and farsightedness.
This procedure is not performed on younger patients without cataracts because the surgery involves entering the eye and, therefore, slightly increases the risk of more serious complications. The surgery also involves removing the natural crystalline lens, which in young people allows them to focus up close. LASIK, which leaves the lens intact, is a better option for younger patients.
Modern cataract surgery, when performed by an experienced surgeon, can allow patients a recovery period rather similar to that of LASIK. In its most sophisticated form, cataract surgery can be performed with eye-drop anesthesia (just like LASIK or PRK) and require no sutures. An outpatient procedure in skilled hands, it takes twenty minutes or less to complete.
Automated Lamellar Keratoplasty (ALK): Automated lamellar keratoplasty (ALK) was done on high myopes prior to the invention of the excimer laser. ALK is not performed today. LASIK has essentially replaced ALK because of the increased accuracy and safety afforded by the excimer laser in making the second "cut." ALK is similar to LASIK in that it uses a microkeratome to separate the surface layer of the cornea. This flap is temporarily folded back (similar to the first part of the LASIK procedure), and a thin disc of corneal tissue is removed with a second pass of the microkeratome. ALK, much less precise than LASIK, was associated with a much higher complication rate. It was primarily used to correct large amounts of myopia.
Satisfactory results are not always obtained the first time, and a high percentage of eyes need additional procedures to achieve the desired result. Sometimes an irregular corneal surface results from the procedure, causing some distortion of vision.
Phakic Intraocular Lens (PIOL) Implants: A phakic intraocular lens (PIOL) implant may correct either extreme nearsightedness or extreme farsightedness. Unlike cataract surgery, your natural lens is not removed; rather, the implant sits in front of the natural lens. In effect, the PIOL becomes an internal contact lens.
Implantable contact lens technology has arisen out of the incredible advances in modern cataract surgery. Current technology allows ophthalmologists to insert flexible intraocular lenses (used to replace the natural lens after cataract surgery) through extremely small incisions. Some PIOL implants, too, are flexible enough to allow folding as they are inserted through small incision openings.
Because of the slightly increased risk of more serious complications, PIOL implants are reserved for high amounts of nearsightedness or farsightedness - beyond the safe limits of LASIK. In places where this technology is available, surgeons are implanting PIOLs in patients with myopia greater than 12.00 to 15.00 diopters and hyperopia greater than 4.00 to 6.00 diopters. In addition, PIOL implants may be preferable to LASIK in patients who fall within the safe LASIK parameters with regard to their prescription but who have thinner corneas, making the tissue removal aspect of LASIK less desirable.
Despite the excellent outcomes in most cases, complications associated with PIOL implants are currently the biggest concern. Specifically, in the early studies, a small percentage of patients developed cataracts shortly after implantation of one brand of the lens There is also a small risk of endophthalmitis (infection within the eye) because the surgical incision actually enters the eye. This rare complication could lead to a complete loss of vision. Endothelial cell loss with some lens designs is also a concern and is being studied rigorously.
Some ophthalmologists in the United States are currently implanting PIOLs as part of an FDA clinical trial. The procedure holds a lot of promise for extremely nearsighted and farsighted individuals. Ophthalmologists are eager to see how PIOL implants fare in current studies using newer lens designs and implantation techniques These lenses are currently being used in Europe and South America with very high success rates. The results of the U.S clinical trial will be presented to the FDA with the hope that it will authorize other eye surgeons to use this exciting new technology.
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