There are two main types of refractive surgery, with new ones on the horizon.
Here’s what you need to know about each type:
LASIK Surgery – Ninety-five percent of the refractive surgeries performed in this country are LASIK (laser-assisted in situ keratomileusis). The procedure permanently changes the shape of the cornea, the clear covering of the front of the eye, using an excimer laser.
Here’s how it’s done: First, your doctor uses a knife, called a microkeratome, to cut a flap in the cornea, leaving a hinge at one end of this flap, much like an open door. The flap is folded back revealing the stroma, the middle section of the cornea. Then a computer-controlled laser emits brief pulses of light, which destroy a portion of the stroma. One pulse removes 0.25 microns of tissue, about 1/70th the thickness of the human hair. Finally, the flap is replaced.
“The results are most predictable, safe and effective,” says Dr. Sandra Belmont. “The recuperation is minimal and there’s no discomfort afterwards. You get your visual acuity back within hours of the procedure and we’re very close to getting what the predicted refractive outcome is anticipated. The results are astounding, really.”
Although nine out of 10 doctors perform surgery on both eyes at the same time, that’s not necessarily the best way to go, says
“Although this is probably the safest procedure we’ve ever had in the history of ophthalmology,” Dr. Salz says, “no surgery is 100 percent safe and I don’t like the idea of rolling the dice with your eyes.”
PRK (Photorefractive Keratectomy) – PRK, the first refractive surgery approved (in 1990) accounts for approximately 5 percent of refractive surgeries today. PRK is still a good option, according to Dr. Salz. The main difference between PRK and LASIK is that instead of cutting the eye, as in LASIK, with PRK the surface layer of cells on the cornea are rubbed off, usually with alcohol. The laser part of the surgery is the same as for LASIK.
“The difference is in the level of discomfort,” says Dr. Salz. “With PRK, because we’re giving them a large abrasion, there’s a fair amount of discomfort for three to five days until those cells grow back.”
During that time, numbing eye drops and antiprostaglandin eye drops can help. This surgery is generally performed in patients with very poor vision who also have a thin cornea and who generally aren’t good candidates for LASIK.
One variation of PRK, called LASEK (laser epithelium keratoplasty), loosens the epithelial cells instead of rubbing them off, making a flap of the cells without actually cutting. In essence, the doctor “rolls up” the cells like a tube of paper, performs the laser procedure, then rolls the flap back down.
“When we do it well, patients may have a bit less pain,” Dr. Salz says, “but I’m not that impressed that there’s really much of a difference.”
On the Horizon
New procedures, both approved and still experimental, offer other options, including a way to improve the vision of people whose laser surgeries have left them with vision problems, and to correct farsightedness and severe nearsightedness. These include:
Intraocular Lenses – These are small focusing lenses inserted in the front third of the eye. They won’t replace laser surgery, says American Society of Cataract and Refractive Surgery President Dr. Marguerite McDonald, but they will be used by patients with more extreme prescriptions who aren’t candidates for laser surgery. All clinical testing is complete and the FDA is expected to approve the lenses within the next year or two.
Customized LASIK, or Wavefront Ablation – This procedure enables doctors to take a more precise measurement of the eye, thus avoiding the night glare and other problems that can plague LASIK patients. It can also be used to correct the vision of those who have already had LASIK. Approved by the FDA in October 2002, the procedure is now available in only a few centers because it requires the purchase of a new, expensive piece of equipment. Its prevalence will likely spread in the near future .
CK (Conductive Keratoplasty) – This non-laser procedure treats farsightedness in people over 40 by reshaping the cornea to change how the eye focuses light. Instead of cutting, CK uses a heat laser to heat and shrink the corneal tissue. The limitation, says Dr. Salz, is that it can only be used on people with very low degrees of farsightedness.
Sclera Expansion – This procedure, still in the early stages of clinical trials, involves laser surgery on the sclera, the white part of the eye, to expand it slightly to provide more room for the lens to expand, thus reducing age-related nearsightedness. It could be performed after refractive surgery to correct nearsightedness.
Overall, says Dr. Salz, refractive surgery “can be a truly life-changing experience for many patients, especially those who were highly nearsighted or farsighted. The accuracy of the procedure still never ceases to amaze me, and I do feel it is one of the most remarkable advances in eye surgery.”