What are the Risks of LASIK surgery?
The risks of LASIK fall into two main categories: Vision Loss Risks, and Nuisance Risks.
Vision Loss Risks
It is very rare to lose vision after LASIK surgery. When vision is lost in an otherwise uncomplicated LASIK procedure, it typically is 1 or less lines on the eye chart of best corrected vision even with extra help from glasses. As such, LASIK surgery has a very good safety profile. Two other ways may exist in which vision could be lost to a more severe degree.
Infection: Since cuts are made on the eye, it is possible that bacteria could gain access to the corneal tissue and start an infection. Scarring from such an infection could lead to vision loss. This is very uncommon as powerful antibiotics are used after LASIK to prevent infection. The risk of severe infection is probably less than 1 in 500.
Progressive corneal warpage (Ectasia): In this condition, the cornea begins to warp in odd directions, leading to loss of vision. Occasionally, a corneal transplant is required to fix this condition. Ectasia, however, typically is seen only in patients with abnormal corneal shapes, or corneal dystrophies, such as keratoconus, even before the surgery is done. Your surgeon will screen your corneas very closely to help identify any preexisting corneal shape irregularity. The risk of ectasia is probably less than 1 in 3500.
Nuisance Risks
Most of the other risks associated with LASIK surgery don’t usually cause a significant loss of vision. Rather, they can cause nuisance problems with the eyes that may not have been present before the surgery.
Dry Eye: Almost everyone undergoing LASIK has some mild dryness, in which the eyes feel somewhat scratchy from time to time during the day. Typically, these symptoms resolve over the course of several months. A small percentage of people, however, have chronically worse dry eyes after LASIK, which may require continuous treatment with drops or dry eye medications.
Night Vision Symptoms: Some patients notice their night vision after LASIK surgery is different than before. Usually, this occurs in the form of halos around streetlights, added glare from oncoming traffic or increased difficulty seeing dimly light shapes in the dark. Typically, these symptoms improve with time. Data from several studies has shown that if 100 patients had such symptoms at 1 month after surgery, only 20 to 30 will still have symptoms by 1 year. Some surgeons believe that a larger pupil size may put a patient at increased risk for night vision problems. However, such complaints can still happen in people with small pupil sizes. Most people with night vision complaints find them only mildly annoying. However, a few individuals may feel that they are unable to function well in low light settings. Medications can be used to change the size of the pupil in low light or nighttime settings, which can help reduce night vision symptoms from LASIK if they occur.
Flap complications: Occasionally, in the process of making the thin corneal flap for LASIK surgery, the flap is made with an irregular edge or a buttonhole in the center. If this occurs, the surgeon will replace the flap on the eye, not perform the excimer corneal ablation, and allow the eye to heal. Little if any vision is usually lost in such a complication. However, it may take several months for the eye to fully heal. Surface laser, such as PRK(link to prk page) can often still be an option for laser vision correction several months later if a problem with the flap occurs during LASIK. The LASIK flap may occasionally become dislodged or wrinkled before it is fully healed. If this occurs, your surgeon will do a minor procedure to put it back in place, usually with no loss of vision. Additionally, cells from the surface of the eye may occasionally start to grow under the LASIK flap, which is called epithelial ingrowth. This is rare in primary LASIK procedures, though may occur more commonly in LASIK enhancements. Often, such cells resolve on their own. Sometimes, though, they require the surgeon to lift the flap and remove the in order to maintain excellent uncorrected vision. Lastly, in the first few days after the surgery, the eye sometimes tries to heal the LASIK wound too aggressively, sending too many white blood cells to the cornea. This condition, called Diffuse Lamellar Keratitis (DLK), usually resolves with frequent steroid eyedrops.
Enhancements: Even though the excimer laser is extremely precise, the fact that the eye is a living tissue and that individual healing response can vary means that sometimes LASIK surgery over or undercorrects the refractive error of the eye. If this happens, a “touch up” LASIK procedure, or enhancement, can be done several months later to correct the remaining refractive error. Enhancement procedures carry a small risk of all of the above complications, just like the original LASIK procedure. Mostly, though, enhancements are just a hassle, as both the patient and the surgeon would have liked to have gotten all of the vision corrected on the first try! In general, about 5-10% of patients undergoing LASIK will need an enhancement procedure to obtain their vision goals.
