by Elizabeth Peterson, MFA
Anatomy and Physiology
The eye is like a camera. The cornea and lens are similar to the camera's lens system. The retina is similar to the camera's film. In the normal eye, light rays pass through the cornea and the lens and focus directly on the retina to produce a clear image. The iris, which is the colored part of the eye, determines how much light is let in.
The cornea is part of the eye that helps focus light to create an image on the retina. This bending and focusing of light is known as refraction.
Reasons for Procedure
Sometimes the shape of the cornea and the eye are imperfect, causing the image on the retina to be blurred or distorted. These imperfections are called refractive errors. Glasses or contact lenses are designed to correct these refractive errors.
Refractive correction techniques can be used to correct three primary types of refractive errors: Myopia, Hyperopia, and Astigmatism.
People with myopia, or nearsightedness, have difficulty seeing distant objects. People with hyperopia, or farsightedness, usually have difficulty seeing near objects and sometimes far objects. Astigmatism can distort or blur vision at all distances and is caused by irregularities in the cornea or lens of the eye. Combinations of myopia or hyperopia and astigmatism are common.
Many patients with myopia, hyperopia, and astigmatism correct their vision with prescription glasses or contact lenses. But for those who wish to reduce their dependence on glasses or contact lenses, refractive surgery, which permanently changes the shape of the cornea, may be an option. The three most common types of refractive surgery are: Radial keratotomy, or RK Photorefractive keratectomy, or PRK Laser-assisted in situ keratomileusis, or LASIK.
RK is performed to treat patients with myopia. In this procedure, the surgeon makes a number of tiny corneal incisions in a spoke-like pattern. This allows the cornea to relax and flatten. RK is rarely done now that newer surgeries are available.
PRK is used to treat patients with myopia, hyperopia, and astigmatism. In this surgery, the surgeon removes thin layers of tissue from the surface of the cornea, and then uses a laser to reshape the cornea underneath.
LASIK is one of the newest methods for permanently reducing dependency on glasses or contact lenses. Like PRK, it can treat myopia, hyperopia, and astigmatism.
Your doctor will schedule a pre-operative evaluation to plan for your surgery. It is best to stop wearing your contact lenses at least 2-4 weeks before this evaluation; the length of time will depend on the type of contact lenses you wear and your surgeon's preference.
Prior to your procedure: do not wear lotion, cream, make up, or perfume within two days of the procedure to decrease the risk of infection. You may be asked to scrub your eyelashes.
Also in the days leading up to your surgery: arrange for a ride to and from the procedure. If you regularly take medications, herbs, or dietary supplements, your doctor may ask you to temporarily discontinue them. Do not start taking any new medications, herbs, or dietary supplements before consulting your doctor.
LASIK is performed on only one eye at a time. Your eye will first be numbed with a drop of anesthetic and an instrument called a lid speculum will be used to hold your eyelid open. Next, a ring-shaped instrument will apply gentle suction to your eye to keep it from moving.
Once the suction ring is in place, a special device called a microkeratome will be attached to it. Using the blade on the microkeratome, your surgeon will cut approximately the outermost 20% of your cornea and lift it carefully to one side.
Using pulses from a computer-controlled laser, your surgeon will reshape your cornea by vaporizing tiny portions of its interior. Your surgeon will then replace the corneal flap into its original position and observe the eye for three to five minutes to ensure rebonding. This type of surgery does not require stitches.
Risks and Benefits
LASIK eye surgery has a relatively low complication rate, but complications can occur. They include, but are not limited to: infection, under-or over-correction of vision, recurrence of previous uncorrected vision, corneal scarring, fuzzy or blurry vision, poor night vision, seeing halos or sunbursts around lights or glare, long-term dryness, scratchiness, or pain in the eye, dislodgement of corneal flap, permanent decrease or loss of vision, and/or the need for additional laser surgery. Potential benefits of LASIK include: reduced dependence on glasses or contact lenses; however, results can never be guaranteed and most people over the age of 40 will still need reading glasses, fast healing with high success rates, and/or minimal discomfort.
In LASIK, as with any procedure, you and your doctor must carefully weigh the risks and benefits to determine whether it's the most appropriate treatment choice for you.
After the Procedure
After the procedure: you will usually be monitored for 1-2 hours before being released, drops will be placed in your eye, you will be given a shield to wear temporarily to protect your eye from injury or pressure, especially while sleeping, you will need to be taken home by a friend or family member.
Once home, be sure to contact your doctor immediately if you experience: eye pain, worsening vision, redness, swelling, bleeding, or discharge from the eye, and/or fever and chills.