Laser eye surgery reshapes the clear front surface of your eye, called the cornea, so that light focuses correctly on the retina. The laser removes microscopic amounts of tissue with extraordinary precision, changing the cornea’s curvature to correct nearsightedness, farsightedness, or astigmatism. The entire reshaping process typically takes less than a minute per eye, though the preparation and different surgical approaches vary.
How the Laser Reshapes Your Cornea
The core technology behind laser eye surgery is a type of ultraviolet laser that breaks apart the molecular bonds in corneal tissue without generating heat. This is a photochemical reaction, not a thermal one, which means surrounding tissue stays completely intact and undamaged. Each pulse of laser light removes tissue to a depth of about 1 micron (one-thousandth of a millimeter), giving surgeons control down to fractions of the width of a human hair.
What the laser actually does depends on what’s wrong with your vision. If you’re nearsighted, your cornea curves too steeply or your eyeball is slightly longer than usual, so the laser flattens the central cornea to reduce its focusing power. If you’re farsighted, the cornea is too flat, and the laser steepens it by removing tissue from the outer edges. Astigmatism means the cornea curves unevenly, like a football rather than a basketball, so the laser smooths it into a more symmetrical shape. In all three cases, the goal is the same: bend incoming light so it lands precisely on the retina instead of in front of or behind it.
LASIK: The Flap Approach
LASIK is the most commonly performed version. The surgeon starts by creating a thin hinged flap in the outer cornea, typically 100 to 160 microns thick. This flap is lifted to expose the deeper corneal tissue, called the stroma. The ultraviolet laser then reshapes the stroma according to a pre-programmed map of your eye. Once the reshaping is done, the flap is folded back into place, where it adheres naturally without stitches.
The flap is what makes LASIK recovery so fast. Because the outer surface of the cornea isn’t removed, the eye heals quickly and discomfort is minimal. Most people notice dramatically improved vision within hours.
PRK: Removing the Surface Layer
PRK takes a different approach. Instead of creating a flap, the surgeon removes the outermost layer of the cornea, called the epithelium, a layer roughly 50 microns thick. This can be done with a brush, a laser, or an alcohol solution. Once the epithelium is gone, the same ultraviolet laser reshapes the exposed tissue underneath.
The key difference is recovery. Your epithelium has to grow back on its own, which takes several days and involves more discomfort than LASIK during that window. PRK is often recommended for people whose corneas are too thin for a flap, or for those in occupations where a flap could be dislodged by physical contact, like military service or combat sports. The final visual results are comparable to LASIK, but reaching stable, clear vision can take a few weeks longer.
SMILE: A Newer, Flapless Option
Small incision lenticule extraction, or SMILE, skips the flap entirely. A femtosecond laser sculpts a disc-shaped piece of tissue, called a lenticule, inside the cornea without opening the surface. The laser then creates a small incision, just a few millimeters wide, through which the surgeon pulls out the lenticule. Removing that disc changes the cornea’s shape in the same way that vaporizing tissue does in LASIK or PRK.
Because SMILE disturbs less of the corneal surface and cuts fewer nerves than LASIK, it may reduce the risk of dry eye afterward. The tradeoff is that it currently treats a narrower range of prescriptions, primarily nearsightedness and astigmatism.
Who Qualifies for Surgery
Not everyone is a candidate. The FDA requires patients to be at least 18, and your glasses or contact lens prescription needs to have been stable for at least a year before surgery. Changing prescriptions suggest your eyes are still shifting, which could undermine the results.
Corneal thickness is one of the most important measurements. Surgeons need to leave at least 300 microns of untouched corneal tissue beneath the treatment zone to prevent the cornea from weakening and bulging over time, a complication called ectasia. Since LASIK also requires tissue for the flap itself, people with corneas thinner than about 500 microns may be better suited for PRK or SMILE, which preserve more tissue. Corneas below 450 microns raise a significant red flag regardless of the procedure.
Other factors that can disqualify you include large pupils, severe dry eye, autoimmune conditions that impair healing, and certain corneal diseases. A pre-surgical screening maps your cornea’s shape, thickness, and curvature in detail to determine which procedure fits, or whether surgery is appropriate at all.
What Recovery Looks Like
After LASIK, you’ll wear a protective eye shield and see your surgeon within the first 24 to 48 hours for a vision test and eye exam. Most people can drive and return to desk work within a day or two. Vision often feels noticeably sharper almost immediately, though mild haziness, glare around lights, and fluctuating sharpness are normal for the first few weeks as your cornea settles.
PRK recovery is slower. Expect three to five days of meaningful discomfort while the epithelium regenerates, often managed with a bandage contact lens and drops. Functional vision returns within a week or so, but fine-tuning can continue for one to three months. For both procedures, you should avoid strenuous contact sports for at least four weeks.
Success Rates and Side Effects
LASIK carries a 96 percent patient satisfaction rate, the highest of any elective procedure. The vast majority of patients achieve 20/20 vision or better, and most no longer need glasses or contacts for daily activities.
Dry eye is the most common side effect. An FDA study found that up to 28 percent of people who had no dry eye symptoms before LASIK reported them three months afterward. For most, this resolves over time with artificial tears, but a small percentage experience persistent dryness. Other possible side effects include glare, halos around lights at night, and reduced contrast sensitivity, particularly in low-light conditions. Serious complications like infection or significant vision loss are rare, occurring in well under 1 percent of cases.
One thing laser eye surgery cannot prevent is the age-related loss of near-focus ability, called presbyopia, which typically begins in your mid-40s. Even after successful surgery, most people will eventually need reading glasses.