If you have a refractive error, such as nearsightedness (myopia), farsightedness (hyperopia), astigmatism or presbyopia, refractive surgery is a method for correcting or improving your vision.
LASIK (laser-assisted in situ keratomileusis) is an outpatient refractive surgery procedure used to treat nearsightedness, farsightedness and astigmatism. A laser is used to reshape the cornea - the clear, around dome at the front of the eye - to improve the way the eye focuses light rays onto the retina at the back of the eye.
First, the eye is numbed with a few drops of topical anesthetic. An eyelid holder is placed between the eyelids to keep them open and prevent the patient from blinking. A suction ring placed on the eye lifts and flattens the cornea and helps keep the eye from moving. With LASIK, an ophthalmologist creates a thin flap in the cornea using either a blade or a laser. The surgeon folds back the flap and precisely removes a very specific amount of corneal tissue under the flap using an excimer laser. The flap is then laid back into its original position where it heals in place. The surgeon will provide eyedrops to help the eye heal and relieve dryness.
Photorefractive keratectomy (PRK) uses the excimer laser in the same way as LASIK, and patients' vision correction results are similar. The main difference between PRK and LASIK is that in PRK there is no flap - only the very top (epithelial) layer of the cornea is removed (or moved aside) before the excimer laser sculpts the cornea.
Many PRK surgeons use a blunt, gently vibrating microkeratome to remove the epithelial layer. The patient may also be given topical antibiotics and anti-inflammatory medications and oral pain medications to reduce discomfort and speed healing after surgery. A "bandage" soft contact lens is used to promote epithelial healing, which takes about four days.
While LASIK patients often report clear, improved vision by the day after surgery, it may be a few days before vision stabilizes for PRK patients. The cornea's epithelial layer re-grows during this time.
A microsurgical instrument called a trephine is used to create a flap of epithelial corneal tissue, and an alcohol solution is used to loosen the epithelial cells. Once the epithelial flap is created and moved aside, the procedure is the same as PRK. After corneal sculpting, the epithelial flap is repositioned and smoothed with a small spatula, then secured with a "bandage" soft contact lens to promote epithelial healing, which takes about four days.