Laser Vision Correction Risks & Complications
Laser Vision Correction, including both PRK and Lasik, are truly surgical procedures, in that they change corneal tissue. This effect is not reversible. As with any surgical procedure, there are individualized differences in the healing response of the eye that may alter the final result. In some cases, these differences may lead to a loss of an eye's best corrected visual acuity. Fortunately, when used appropriately, PRK and Lasik rarely lead to this complication. Also common to all surgical procedures is a risk of bacterial infection after the procedure. This also is a very rare complication, due to careful pre-operative preparation and surgical technique. Postoperative antibiotic eye drops also help prevent infection. If a bandage contact lens is required for postoperative comfort after PRK or Lasik, the risk of infection is slightly increased.
The most common "complication" of Laser Vision Correction is that the vision still requires glasses or contact lenses to be perfect. This is not actually a complication, but rather is a realistic expectation about what can be achieved by Laser Vision Correction. There may always be a slight prescription that could possibly improve the vision more even after Laser Vision Correction. There may be some individuals who might require a prescription lens to be used for more intensive visual tasks, such as night driving. If the vision remains significantly poor without correction after surgery, a retreatment or enhancement may need to be performed. In Lasik, this is usually done at least 3 months after the initial surgery. For PRK, a retreatment might be done 6 months to 1 year after the initial surgery. Retreatments are provided at no additional charge to the patient.
Some patients report a reduction in other measures of vision after Laser Vision Correction, such as contrast sensitivity, while still maintaining an excellent measured visual acuity. This may reduce the ability to see objects in sub-optimal viewing conditions, such as making out shapes in the fog, etc. Additionally, some patients are bothered by glare and halos around lights, especially at night, after Laser Vision Correction. It may be advisable for patients with occupations that are extremely visually demanding, especially at night, to strongly consider these possibilities when contemplating Laser Vision Correction.
Some patients over the age of 40 may find that they require reading glasses to read after Laser Vision Correction, whereas before, they could read by taking their glasses off. This is because of presbyopia, or the natural decline in the ability to focus at near as one ages. If an eye is nearsighted, it has a naturally close point of focus when uncorrected (no glasses or contact lenses). When this nearsightedness is corrected by Laser Vision Correction, this near focusing advantage is lost. In this situation, the person has the option to use reading glasses to read, or one eye can be "set" intentionally nearsighted with Laser Vision Correction for reading. There is no actual refractive surgery procedure available to correct presbyopia.
Complications specific to Lasik
Lasik involves two surgical steps, the creation of a corneal flap using a microkeratome, and the treatment of the underlying corneal bed with the excimer laser. There may be potential complications related to each of these steps.
Microkeratome related complications
- Although the microkeratome is meticulously cared for and examined before each case for proper functioning, there are situations where the microkeratome does not properly perform and the case may have to be rescheduled. If the microkeratome jams during the creation of a flap, or if it creates a flap that is too thin or imperfect, continuing with the case and performing the laser treatment may lead to visual problems or healing problems. In this situation, it is preferable to place the flap back in position and allow it heal without performing the laser treatment. At a later date, the case can be repeated (at no additional charge). While inconvenient to the patient, dealing with the situation in this way leads to a much better result than using the laser after creation of an imperfect flap.
- In some cases, the microkeratome may create a "free cap" rather than one with a hinge. In this situation the surgery can usually be completed, but a suture may be required to keep the flap in place. This suture typically will not cause problems, and can be removed in the office at a later date.
- If the flap created by the microkeratome is very thin, there may be a mild blurring of vision post-operatively for a period of time while this heals into place.
- Some individuals have very deep set eyes, or a very small opening between the eyelids. In these cases, it may not be possible to apply the suction ring for the microkeratome. In this situation, PRK could be performed instead, or a small incision at the corner of the eyelids may allow Lasik to be performed.
Laser related complications
- A variety of factors can affect laser function, including room humidity and airborne debris. For this reason the laser is tested before each case. If it is found to be functioning improperly and the problem cannot be solved, the case may have to be rescheduled. Typically, this would happen before any surgical manipulation of the eye would have taken place.
- If the patient is unable to maintain fixation on the fixation light of the laser, a "decentered" laser treatment may occur. This can lead to significant visual problems after surgery, and may be difficult to treat.
- Sometimes the central part of the treatment area remains under treated, leading to a "central island". This can lead to post-operative visual complaints of ghost images or double vision. Usually, this resolves with time, but in some cases retreatment is necessary to remove the island.
Post-operative Lasik complications
- In rare cases the flap created by the microkeratome may slip out of position, usually in the immediate post-operative period. This may be caused by eye rubbing, or incidental trauma immediately after the procedure. This is prevented by avoiding actions that could displace the flap, and by using appropriate eye protection after surgery. Usually the flap can easily be repositioned in the office, but sometimes a suture may have to be placed to hold the flap in position. This suture can be removed in the office at a later date.
- In rare cases, inflammation may develop between the flap and the corneal bed post-operatively (DLK). Usually, this is treated with anti-inflammatory eye drops for a period of time. Sometimes the flap may have to be lifted and irrigated in the office. After this is done, the healing process will usually proceed normally.
- In some cases, an eye may feel dry for a period of time after Lasik is performed. This is treated with artificial tears, and sometimes with plugs that block tear drainage from the eye (to improve lubrication).
- In rare cases, cells covering the surface of the cornea grow underneath the flap. If this is significant, the flap may have to be lifted and the cells removed.
Complications specific to PRK
- The most common adverse events after PRK are glare, halo, and haze, especially at night. While 10% experienced this to some degree at 6 months after PRK, only 2.4% experienced slight glare and halo at one year. This data is from clinical studies looking at the treatment of low to moderate nearsightedness with little or no astigmatism with PRK. Treatment of high levels of nearsightedness or treatment of nearsightedness with astigmatism may lead to higher rates of these visual effects. Again, most cases subside with time.
- Short term complications directly after PRK include pain (24-48 hours), scratchy sensation, light sensitivity, and temporarily blurred vision. Medications can help with symptoms during this time period, as can the use of a bandage contact lens.
- More rare adverse events include trouble with night vision, over- or under-correction, loss of best corrected vision (see above), increased eye pressure due to usage of post-operative medications, and very rarely corneal infection or scarring. Often a haze is visible in the area of treatment by PRK when the cornea is examined by the high magnification equipment of an eye physician. This haze, unless unusually severe, rarely affects the vision, and usually disappears with time.
- Laser related complications: In very rare circumstances, the laser may not operate properly and give an uneven treatment to the eye, or the treatment may not be perfectly centered over the pupil. This can lead to undesirable visual effects, and may require retreatment. Sometimes "central islands" form in the center of the laser treatment area, leading to visual side effects such as seeing ghost images. Most lasers today have a program built in to prevent this problem. If central islands do occur, they usually resolve with time, although sometimes retreatment may be required to fully eliminate them.