Potential Side Effects

Less Common

Loss of best-corrected vision: Best-corrected vision refers to visual acuity, at any moment in time, while wearing the best possible eyeglasses. Therefore, best-corrected vision can be measured both before and after laser vision correction.

Prior to surgery, laser vision correction patients typically have a best-corrected vision of 20/20 or slightly better (20/15). While most achieve 20/20 without correction, of those who don't, it is important to document whether 20/20 is still possible with eyeglasses. If 20/20 with eyeglasses remains intact, uncorrected 20/20 vision can usually be achieved with a second laser treatment. However, if 20/20 is no longer possible, even with eyeglasses, retreatment is more problematic and occasionally not advisable. Patients who have had laser vision correction, are no longer able to see 20/20 with glasses, and can't have another laser treatment are said to have lost best-corrected vision.

The laser manufacturers are required to document the incidence of loss of best-corrected vision as part of the FDA approval process. The standard is to report patients whose vision decreases by two or more lines on the eye chart. This occurs in roughly 1 out of 500 cases with modern lasers. Patients with high degrees of nearsightedness/astigmatism and those who are farsighted are at higher risk.

Decreases in best-corrected vision are typically mild. Some patients are aware of a loss of sharpness and clarity, while others don't notice the decrease, even though it is measurable on the eye chart.

Decentration refers to placement of the laser treatment off-center from the optimal centration point. Visually significant decentrations are extremely rare when experienced surgeons use modern lasers.

Flap dislocation is another issue unique to the flap procedures LASIK and IntraLASIK. While flaps heal quite effectively for everyday life, extreme trauma, such as a punch to the eye or an automobile airbag deployment, could conceivably dislodge a previously healed flap. For this reason, police officers, prison guards, military personnel, boxers and others whose activities put them at risk for extreme eye trauma sometimes elect for flapless procedures.

Ectasia is one of the more significant potential complications of laser vision correction. Ectasia occurs when the cornea is thinned too much and a region of it begins to bulge forward, leading to a distorted, irregular contour. Mild ectasia causes visual distortion that can still be corrected with glasses. With moderate disease, gas permeable or hard contact lenses are necessary to mask the distortion, and advanced cases are treated with corneal transplantation.

The risk of ectasia is correlated with the initial corneal thickness, the presence or absence of a flap and the amount of laser correction needed. These issues are discussed in greater detail under the topic of thin corneas.

Bad flaps: One of the reasons LASIK is so popular, is that complications during the actual procedure are quite rare. However, out of the entire procedure, LASIK surgeons worry about the flap creation step the most, as a bad flap means the procedure must be aborted without doing the laser treatment. Bad flap examples include flaps that are too small, off-center or ones that have a ridge, buttonhole or tear.

An aborted surgery naturally leads to a very disappointed and worried patient. Fortunately, most bad flaps heal so that the vision returns back to the way it was before anything was done. If desired, another flap can often be made after three months of healing or a flapless procedure such as PRK, LASEK or Epi-LASIK can be considered.

LASIK surgeon experience plays a considerable role in the frequency of flap problems. Experienced surgeons with modern equipment have reported flap complication rates around 1 in 1000. Inexperienced surgeons can have rates closer to 1 in 150 and sometimes higher.

Flap creation with the Intralase laser may be of benefit when potential flap complications are of particular concern. While bad flaps are still possible with the Intralase, proponents believe they occur less often than with the standard microkeratome. On the other hand, flapless surgery is undergoing a mini-renaissance, in part because flap complications are impossible when no flap is made.

Infection is an extremely rare but serious potential complication of all vision correction procedures. The rate of infection with LASIK has been estimated at 1 to 2 per 10,000 cases. By comparison, a recent study published in Ophthalmology by Johns Hopkins Wilmer Eye Institute showed an infection rate of 18 per 10,000 per year with CIBA Vision Night and Day contact lenses.

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