Vision by Pacific Cataract and Laser Institute

Potential Side Effects

Side Effects & Risks


  • Side Effects

  • +Problems with the corneal flap

    If your eye were to suffer injury early in the healing process, the flap could be dislodged and require immediate repositioning.

  • +Undercorrection or overcorrection

    Because every eye responds a little differently to LASIK, it is possible that the desired correction may not be achieved. Most cases can be retreated with an enhancement procedure, but corrective lenses may also be necessary.

  • +Contact lens intolerance

    LASIK changes the shape of the cornea and there is a chance that contact lenses, if they are needed, may not fit easily or comfortably over the new surface.

  • +Microscopic corneal irregularities

    It is possible that very small surface irregularities could result in a loss of best-corrected vision. There is a risk (less than 1 in 100) that two or more lines of vision on the eye chart could be lost.

  • +Regression

    Sometimes, especially with people who undergo high amounts of correction, the effect of surgery is partially lost over several months. In some, but not all cases, significant regression can be retreated.

  • +Halo effect

    Halos are an optical effect that may be noticed in dim light situations when the pupil dilates larger than the area of correction. As the pupil opens, a second ghost or faded image is produced by light passing through the untreated outer area of the cornea. Although this could interfere with night driving, it is rarely a significant problem.

  • +Inconvenience between surgeries

    When both eyes are not treated the same day, the difference in correction can result in them not functioning well together.

  • +Presbyopia or reading glasses

    An advantage of being nearsighted is that it may take until age 50 to be affected by presbyopia. However, if you are nearsighted and have successful LASIK treatment, you may need reading glasses in your early 40s, as is normal for most individuals.

  • Risks

  • +Epithelial cell in-growth under flap (1 in 500 cases)

    Epithelial in-growth is more common with patients over age 50 and with patients who have epithelial-adherence problems from other causes. Retreatment involves lifting the flap and clearing the cells away. In most cases, in-growth is limited and no retreatment is required. If the in-growth is progressing and is not cleaned, the corneal flap may be distorted and the vision affected.

  • +Abnormal corneal flap (1 in 5000 cases)

    If an irregular flap is made, it may not re-heal properly and result in some loss of visual quality. Irregular flaps can be caused by inadequate or lost suction of the microkeratome’s suction ring, blade abnormalities and microkeratome malfunctions. The risk is higher for patients with very flat corneas and those with very high degrees of nearsightedness. Even with very experienced surgeons and careful testing of instruments, corneal flap irregularities can occur. Other corneal flap problems include short or incomplete flaps. If this occurs, the incomplete flap is simply closed and the procedure is repeated 3 to 4 months later. Other than inconvenience to the patient, this complication rarely has any permanent consequence.

  • +Free corneal cap - no hinge (1 in 2000 cases)

    An inadequate or absent hinge may produce a free corneal flap or cap. However, since the original LASIK technique created a hinge-less cap, this is not a complication in the true sense. If a free cap occurs, the procedure is continued and the cap is simply replaced after the surface is treated.

  • +Debris in flap interface – enough to affect vision (1 in 5000 cases)

    Some people’s tear secretions contain more mucus or oil than normal. Despite the surgeon’s best efforts to keep tear secretions out of the treatment area, it is possible for enough of this material to become trapped under the flap to affect the quality of vision. If this occurs, the flap can be lifted and the debris can be removed.

  • +Inflammation – enough to affect vision (1 in 2000 cases)

    A condition known as “Sands of the Sahara” can develop in the hours and days after LASIK treatment. While it is unclear exactly what causes this condition, it seems to be an immune reaction to a substance that comes in contact with the flap interface. The inflammation produces a granular haze within the flap and can affect visual quality. Topical steroids are the normal treatment and in rare instances, the flap is lifted and flushed.

  • +Ptosis – permanent droopy eye lid (no cases; less than 1 in 10,000)

    Theoretically any eye surgery can result in enough inflammation and swelling to cause sensitive eyelid tissue to stretch. If stretched too far, a droopy eyelid could result. The chances of this are extremely rare and eyelid surgery can repair lasting droopiness.

  • +Infection (no cases; less than (1 in 10,000 cases)

    If bacteria were to grow under the flap, the resulting infection could cause permanent scarring. This has not occurred at Pacific Cataract and Laser Institute.

  • +Corneal thinning requiring corneal transplant (1 in 10,000 cases)

    Rarely a cornea will be weak enough that, after it is thinned by LASIK, it will partially give way and create distortion with blurred vision. As a precaution, we measure the thickness of the cornea before the procedure. In the rare instance that a thin cornea causes distorted and blurred vision, a corneal transplant is required. After transplant surgery, vision is normally good but not perfect.

  • +Loss of corneal flap (no cases; less than 1/10,000)

    If a serious microkeratome malfunction were to occur, the corneal flap could become unhinged. If separated from the eye, the potential exists for the flap to be damaged beyond repair or lost. A complication of this nature might require additional surgery.

  • +Corneal perforation (no cases)

    This complication is not possible with the microkeratome presently used by our surgeons.