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Other Vision Correction Options at the Hamilton Laser Eye Institute in Hamilton Ontario
AK (ASTIGMATIC KERATOTOMY) AK is used to correct astigmatism. A diamond blade is used to create two small accurate incisions in the periphery of the cornea. It causes the warped cornea to relax to make it round. This proven procedure is still used in selected cases. ALK (Automated Lamellar Keratoplasty) for Farsightedness Is a useful procedure for farsighted correction. Like ALK for nearsightedness, this procedure uses a keratome to create a flap of corneal tissue from the surface layer. Unlike ALK for nearsightedness, there is no second pass of the keratome to remove tissue. The original surface is simply replaced, and the eye is allowed to heal. If no tissue is removed, then how does the procedure work? To explain, think back to when you were a child and may have gone swimming using an old tire inner tube for a float. There was always one area of the tube that would pouch out further than the rest, because the wall of the tube was thinner in that area. Hyperopic ALK works on a similar principal. This pass of the keratome is set to a depth of around 70% of the cornea’s thickness, allowing it to bulge slightly in that area. The result is that the eye’s curvature is made slightly rounder, thereby increasing the corneal power, and reducing or eliminating the farsightedness. ALK is very popular with patients because healing is rapid and visual recovery is usually immediate, within 24 hours of surgery. However, there are limitations to the procedure. The limitations of ALK for farsightedness are in the accuracy of the procedure and in the range it can treat. ALK can only cure farsightedness up to 4 or 5 diopters, which is often not enough to eliminate the condition entirely. Further, beyond 3 diopters of correction, corrections become less predictable. Finally, long term results are not known, since the procedure has only been performed since the late 1980’s. ALK (Automated Lamellar Keratoplasty) for Nearsightedness ALK is a procedure that has been replaced by LASIK in recent years. ALK is performed in two steps. Both steps utilize an instrument that is much like a carpenter's plane in design, called a microkeratome. In the first step, the microkeratome creates a thin flap of cornea. The flap is lifted to expose the inner layers of the cornea. Then a second pass of the keratome is made to remove tissue, flattening the eye to improve the focus. The flap is then replaced and allowed to heal. The disadvantage of ALK is that it is not nearly as accurate as the excimer laser for the removal of tissue, so multiple procedures are sometimes needed to achieve the final correction. Contact Lenses Are a popular alternative to glasses. Contacts are worn by approximately 25% of the people who need some sort of correction. They provide excellent peripheral vision, permitting a wider range of activities than glasses, with no change in appearance. Problems with contact lenses include their cost, maintenance hassles, the possibility of infection and intolerance due to sensitivities. Glasses Are the most common solution to correct refractive errors because of easy maintenance and low cost. The drawbacks to glasses are obvious - they interfere with activities, change a person’s appearance, and require care. Additionally, glasses typically reduce peripheral vision. Lens Extraction with Implant Lens extraction with implant is performed for eyes with larger amounts of farsightedness, especially in older individuals. This procedure is essentially the same as the procedure done for cataract surgery. The natural lens is removed and an implant lens is placed into the eye instead. In this procedure, the eye is carefully measured so the power of the implant lens can be matched to the eye, reducing or eliminating the need for glasses. Because the implant lens is made of rigid plastic, it cannot fine tune the vision to focus for objects at near. In older individuals, this is nothing new, since the natural lens stops focusing for near vision in the mid-forties. However, in younger people this can be an issue, and is an important consideration to bear in mind. The advantages of lens extraction with implants are many. With modern techniques, the surgery is very rapid, very safe, and heals quickly. It can reach higher prescriptions than any of the other refractive procedure. However, this surgery (unlike LASIK) involves entering the eye, so there is greater concern about infection. Still, in the appropriate setting, this procedure can deliver very dramatic results with great accuracy, and it is increasing in popularity. LTK (Laser Thermal Keratoplasty) LTK uses heat to change the shape of the cornea, increasing its curvature and reducing or eliminating farsightedness. In LTK, the Holmium (infrared) laser is used to treat the periphery of the cornea causing the tissue to shrink slightly, tightening the cornea like a belt causing it to become more curved.
PRK (PHOTOREFRACTIVE KERATOPLASTY) PRK was the first way the excimer laser was used in refractive surgery. In PRK the top protective layer of the cornea (epithelium) is removed to expose the inner layers of the cornea. The excimer laser would then reshape the inner layers of the cornea. A bandage contact lens would then be placed on the cornea 1 to 3 days while the epithelium grew back. The disadvantages of PRK were slow visual recovery, post-operative pain and corneal scarring. PRK has largely been replaced by LASIK for these reasons.
RK (Radial Keratotomy) RK is the oldest of modern refractive procedures. Over 1 million RK procedures have been performed in North America since the late 1970's. RK corrects mild myopia by using a diamond blade to make radial incisions in the front surface of the cornea. This procedure has largely been abandoned because of its limitations and potential complications. |
A hyperopic is shorter than the normal eye. Due to the shortness of the eye,
the light rays converge at a point past the retina resulting in blurry vision
for close and far away objects. 
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