LASIK Laser Complications - include but are not limited to:
1. Undercorrection
Undercorrection occurs when the laser has not removed an adequate amount of tissue. Regardless of how carefully a correction is calculated, and a laser is calibrated, various factors can affect the outcome of the procedure.

These factors include but are not limited to:

  • Aftershave/perfume and/or any other scented products
  • Tissue density and composition which can modify the effect of the laser and the resulting amount of tissue removed
  • Room Temperature and Humidity
  • Regression - In some instances, during the healing process, portions of the treated tissue returns to it's original state thus reversing the results of the treatment.

Enhancement or retreatment is usually an option and best uncorrected visual acuity may still be obtained.

2. Overcorrection
This occurs when the laser has removed too much tissue. It also commonly occurs in the immediate postoperative period as a result of the normal swelling which occurs after any surgical procedure. Tissue swelling is expected to subside within a few days to 2 weeks. Overcorrection can also occur due to the factors as outlined for undercorrection. Enhancement or retreatment is usually an option and best uncorrected visual acuity may still be obtained.
3. Decentered ablation
A decentered ablation is caused by one or more of the following:
  • Significant patient eye movement during the laser treatment
  • Incorrect centering of the laser beam

A decentered ablation can cause:

  • Optical aberrations and irregular astigmatism
  • Glare, starbursts or contrast sensitivity problems

Depending on the severity of the problem and the location of the ablation it may be possible to correct these symptoms.

4. Too small an optical zone
This can occur when the optical zone is smaller than the nighttime (dilated) pupil. It is more common in people with very large pupils or very large corrections. Nighttime glare can be a significant problem and in the worst case scenario could for instance stop one from driving at night. See The LASIK Envelope for more details. 
Flap and Operative Complications - include but are not limited to:
1. Dry Eye Syndrome and Symptoms
Dry eye syndrome is not exclusive to people who have had refractive surgery, however, it has developed into the most common complication after laser vision correction, affecting what now appears to be the majority of all LASIK patients.
2. Incomplete, irregular, or decentered flap, or button hole of flap
This complication occurs at the time of flap creation and is very rare. The most common cause is a loss of suction, or discrepancy in the fit of the eye surface to the suction plate. Occurrence of any of these flap complications will require postponement of the procedure until the flap has healed (approximately 3 to 6 months later). The flap is immediately replaced to it's original position and your vision will usually return to it's original state within a few days to a week.
3. Free cap
This complication also occurs at the time of flap creation and is more rare than the one above. It is more common in patients with a flatter curve on their eye surface. Depending on the situation laser treatment may or may not proceed. At the commencement of all procedures alignment marks are placed on the surface. These are mostly used to perfectly realign the flap at the end of a normal procedure, but are also invaluable in the unlikely event of a free cap.

If the flap and flap bed is normal your surgeon may elect to continue with the procedure because the flap replacement process is very similar to what is done with a normal hinged flap. If the flap or flap bed is incomplete or irregular in any way (see #1 above) the surgeon will postpone the procedure until the flap has rehealed.

4. Epithelial (surface) abrasion at the time of flap creation
This also occurs at the time of flap creation and is more common than the two complications listed above. This is more likely in older patients (45 and above) and most commonly results if there is a weakness or deficiency in the adhesion of the surface epithelium to the sublayer basement membrane (cross section of Cornea).

In general, if this condition exists in one eye it usually occurs in the other eye. If this condition exists the surgeon will use a bandage contact lens to reduce the post operative discomfort and assist with surface rehealing of the cornea. The recovery time may be extended an extra day or two (until the surface heals), and usually the visual results are comparable to those of a patient who did not experience this complication.

The body deals with healing an epithelial abrasion in much the same manner as it heals the edges of the flap. The contact lens is best left in until the surface is totally healed.

5. Wrinkles in the flap
Wrinkles most commonly occur when a patient rubs or squeezes their eye too tightly in the first few hours following the procedure. It is common practice to have your eye examined with a slit lamp - prior to discharge from the clinic - in order to ensure that your flap has not moved from where the surgeon put it immediately after your procedure.

If the wrinkles are visually significant it may be possible to smooth them out with a process that is similar to ironing. The alternative is to lift the flap and repeat the initial smoothing process. If the flap does need to be lifted, epithelial healing will be delayed for an additional day.

6. Debris under the flap
This is fairly common because of the fact that the tear film normally has particles of oil and other material such as make up, lint from clothing, etc. The loose cells which result from the flap creation can also contribute to the debris found under the flap. These loose cells can cause the most problems because they may continue to grow under the flap.

Your surgeon will take great care in washing under the flap and cleansing the area of any debris, and will verify that there is no debris remaining when examining your eyes under the slit lamp prior to your leaving the clinic. If your surgeon is not happy with what he/she sees they may elect to re-lift the flap and cleanse the area again.

7. Displaced flap
This is an unusual occurrence which occurs from rubbing or trauma to the eye within the first 24 to 48 hours after the surgery. This is the time period in which the tissue begins the process of repairing itself and "glues" the flap in place. This risk is decreased as with time and is normally very minimal after three months, however, flaps can and are lifted many months later for retreatments.
8. Inflammation under the flap
(Sands of Sahara Syndrome or Diffuse Lamellar Keratitis [DLK])
This occurs when the tissue under the flap reacts to minute traces of microorganism toxins. All microorganisms and most of their byproducts are destroyed with heat sterilization. Unfortunately, some microorganism toxins are not destroyed by heat and even in very minute amounts can cause an adverse reaction. This reaction is an inflammation (not an infection) and likelihood of this occurring is based on each patient's sensitivity and/or the amount of exposure. Should this unlikely event occur it can usually be well controlled with steroid drops, although in extreme situations it may be better to lift the flap, wash out the inflammation and place steroids directly on the affected tissue.
9. Infection
This is an extremely rare occurrence, although should it occur it could be devastating. It is normal practice to use antibiotics in the post operative period and this combined with most people's natural resistance prevents this from occurring.

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For more information contact:
Dr. Murray McFadden
(BSc, MD, FRCS(C), Diplomate of the
American Board of Ophthalmology)
© Copyright 1996-2005 Murray McFadden MD, Inc.

Telephone: (604) 530-3332
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This page last updated on September 24, 2001.
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