Refractive surgery procedures is the safest and most successful interventions made on the human body. However, each procedure hides the possible risk of complication (though rare) for which we must be informed.

Refractive surgery complications (undercorrection or overcorrection)

Laser surgery may lead to either overcorrection or undercorrection due to the patients' different healing method and other surgical parameters, leaving patients with residual myopia, hyperopia or astigmatism. These may require the patient (not necessarily) to wear glasses, lenses or undergo further surgery.

Overcorrection frequency: 1 in 100 patients

Undercorrection Frequency: varies according to the patient's prescription, for example, 4 patients in 100 with 4D myopia, 8 patients in 100 with 8D myopia.

Loss of best corrected vision

A small number of patients may experience a slight loss of visual acuity following laser correction. This means that after your surgery even when wearing glasses or lenses, you may not see as clearly as before the surgery. In most cases, acuity returns within a period of 6 to 12 months.

Frequency:  1 in 100 patients


Regression refers to the tendency of the eye to drift back slightly toward its original prescription after laser correction. In most cases regression is low and is taken into consideration when your surgery is being planned. Often, all that is needed for patients who experience regression problems are glasses during night driving.

Frequency: 1 in 100 patients

Night Glare

Even before undergoing laser correction, many people have poor night vision of night glare ("halos", "starbursts") when wearing glasses or contact lenses.

Night glares are common immediately after surgery and usually lasts 3 to 4 months. Once both eyes have been treated, or six months have passed after surgery, the night glare tend to decrease and the vision should return to its original condition.

Frequency of severe night glare: 1 in 50 patients


The haze due to healing is caused by the collagen protein that develops on the surface of your eye, especially after PRK surgery. It is not visible to the naked eye. Although it can be treated in most cases, it usually gradually clears up over many months after surgery.

Frequency of severe cases 1 in 1000 patients

Epithelial ingrowth

Produced when epithelial surface cells grow underneath the corneal flap during the healing of the corneal incision. It usually occurs during the first month and is more likely in patients with a weak adhesive protective layer for which age is a parameter. The development of epithelial ingrowth is more common in cases of trauma or rupture of the epithelium. This situation more frequent with LASIK surgery and long-term contact lens wearers. Although most small areas of epithelial development need only monitoring, large areas require the lifting of the flap and cleaning of the cells.

Frequency: 1 patient in 100


The most serious complication. This is probably the greatest risk during the first 48-72 hours after surgery. Most of the minor infections are treated and eliminated quickly. On rarer occasions there are infections of the cornea (keratitis) that can seriously affect the eye and ultimately our vision.

Frequency of serious infection 1 in 5000 patients

Complications of corneal flap

The corneal flap must be clinically sufficient in quantity, thickness, size to proceed with laser treatment. Corneal flap complications risks range from cases that simply require postponing the intervention of 3-6 months, to circumstances that create permanent corneal irregularities resulting in blurred vision.

The corneal flap complications that occur after the LASIK procedure during the recovery period include displacement, flap wrinkles and epithelial increase. Although only 1% of patients have complications with the LASIK procedure, fewer still have serious flap-related complications.

Prevalence: : 1 in 500 patients


Keratectasia is a serious long-term complication, during which the cornea weakens, retreats and causing bulging forward and consequently resulting on a high degree and irregular astigmatism and a decrease in vision. It is important to be diagnosed early on so it can be addressed. There are presently ways to deal with this such as cross linking where ultraviolet radiation is used to stop the progress of this pathological condition.