The method of changing the optical measurements of the eye by means of an operation is called refractive surgery. Its popularity began with the introduction of radial keratotomy or RK in the 1980s. Russian doctors were able to correct mild degrees of nearsightedness or myopia by creating micro incisions in the outer part of the cornea.
The cornea is the transparent front part of the eye that accounts for two-thirds of the total focusing power of the eye. The small cuts made on the misshapen cornea flatten it to reduce short-sightedness. Since then, more up to date procedures have largely replaced radial keratotomy. Its use now is mostly to treat patients with astigmatism and have cataracts as well.
Basically, there are two basic types of corrective refractive surgery. One is by changing the curvature of the cornea through laser surgery and the other is by replacing the natural lens of the eye.
The more current refractive surgical procedure involves the use of modern eye lasers. This includes photorefractive keratotomy or PRK, laser in situ keratomileusis or LASIK, and laser in situ epithelial keratomileusis or LASEK.
All of the three procedures utilise lasers to permanently change the shape of the cornea. People with steeply curved corneas or those who have eyes that is longer than normal experience blurred vision and are said to be short-sighted or myopic. Other people are hyperopic or longsighted because their corneas are too flat or the eyeball is too short. Others have astigmatism, a condition that produces blurred images at all distances because the cornea is abnormally curved and causing vision to be out of focus.
In the recent years, radial keratotomy has been replaced excimer laser surgery because it can be used not only for short-sightedness but also for other refractive errors like long-sightedness and astigmatism.
Laser eye surgery is an outpatient procedure and both eyes can be treated on the same day unless the eye surgeon decides otherwise. Before the procedure, local anaesthetic drops are place in the eye to minimise discomfort that may be experienced by more sensitive patients. The advantage of refractive laser surgery is that the results are constant and predictable. Recovery is very rapid, no postoperative pain, and vision is noticeably improved almost immediately after surgery.
For those who have higher degrees of myopia or hyperopia, another refractive correction procedure involves removing the natural lens of the eye and placing a replacement lens with the correct focusing power. It is very much the same as cataract surgery, where the clouded lens is replaced by silicone or plastic lenses.
A small incision is made in the eye for artificial lens insertion. Recovery is about a week after surgery, compared to almost immediate improvement for laser surgery, particularly LASIK.
Refractive lens replacement is mostly suitable for older patients who are severely short-sighted or severely longsighted. This has been used since 1999 to treat people with severe myopia and hyperopia. For those who are approaching the cataract age group, which is around 45 years old, this procedure is often the best choice to correct blurred vision.
There are some advantages in having intraocular lens surgery over laser surgery. Those who are not suitable candidates for LASIK can opt for lens replacement. In patients with cataracts, the removal of the natural lens means that the cataract will not recur.
The drawback with conventional lens replacement is that these are mainly focused for distance vision. This means that patients cannot change focus from far to near and vice versa.
To compensate for this problem, newer artificial lenses that are able to accommodate or adjust to see multiple distances have been manufactured. Just like the normal eye, these lenses use the muscles in the eye to bend the lens in order to focus correctly.
There are also multifocal lenses that work much like bifocal glasses to allow patients to see different distances. Unlike accommodating lenses, multifocal lenses do not bend, but instead allow patients to see various distances through the different parts of the lens.
Both accommodating and multifocal lenses aim to improve focus of vision without having to use eyeglasses.
All of these methods of refractive surgery are intended to improve the quality of life, minimising or even doing away with the need for corrective eyewear. Whether the choice is laser surgery or refractive lens exchange, the outcome will depend on the expertise of the doctor as well as the eye care practices of each patient after surgery.