LASIK Educational Material
Laser Eye Surgery in Denver, Colorado
LASIK Risks and Complications
Part One (on a new page)
Intra-operativePart Two (on a new page)
Post-operativePart Three
Quality of vision
Risks associated with laser vision surgery range from occasional
minor temporary setbacks to rare major permanent conditions.
(Click on any topic or scroll down)
Over-correction, Under-correction or RegressionNight or dim-light vision complications
Over-correction, Under-correction & Regression
Every eye heals differently. Surgical plans are generally based
upon an "average eye" healing response. Recall that these
plans are typically quite accurate for most people, yielding a 98%
rate of 20/20 vision after 12 months in the FDA validation study of
VISX CustomVue.
If your eye heals in a different manner (more aggressively or slower) than the "average eye", an over or under correction of the refractive error may result.
In addition, after LASIK, the stroma (the thickest part of the cornea and where the laser ablation takes place) may experience some slight remodeling, and/or the epithelium (the thinnest and outermost layer of the cornea) may thicken.
Either of these conditions might result in a slight loss of refractive surgical effect postoperatively. This loss, or going back towards the original refraction, is called regression; this would represent a patient under-responding to the laser.
Conventionally, regression is defined as a shift in visual outcome. In this situation, the sharpness of vision that occurs soon after surgery diminishes as the eye regains a small amount of its original nearsightedness, farsightedness, or astigmatism. Regression can occur quickly, within the first few weeks after surgery, but it also can occur slowly over time.
Patients who experience regression will notice their vision changing progressively over days and weeks (not as a fluctuation during the day). Typically, the Dr. Cutarelli will evaluate the regression to determine its cause and review treatment options with you. An enhancement procedure can usually be performed to correct the residual error, just as is done to treat an under-correction or over-correction.
In general, the higher the correction undertaken, the more likely regression is to occur;this is especially true for treatment of hyperopia greater than +5 diopters, which may benefit more from Clear Lens Extraction.
In most cases, under-correction (where the patient's cornea responds insufficiently to yield the desired change in vision) and regression (where part of the surgical effect is lost during the healing process) can be treated with an enhancement procedure.
An over correction of myopia may be corrected by performing a hyperopic LASIK enhancement, whereas a hyperopic over correction would, in most cases, be correctable using a myopic LASIK enhancement.
However, eyes with very thin or steep corneas or high degrees of refractive errors may not be eligible for enhancements. If this refers to you, be sure to speak with Dr. Cutarelli about your potential eligibility for an enhancement.
Overall:
· Nearsighted patients who experience an over-correction become farsighted and notice that they can no longer see near objects as well· Nearsighted patients who have been under-corrected notice that objects in a distance are still not perfectly clear although vision is still typically better than preoperatively
· Farsighted patients who experience an over correction become nearsighted and notice that objects at a distance are still blurred although near objects can be seen more clearly.
· Farsighted patients who have been under-corrected notice that both far and near objects are not totally in focus, just as with the original hyperopia, although typically still improved from the pre-LASIK vision.
If you are among the relatively few people who significantly over-respond or under-respond to the laser treatment, Dr. Cutarelli will discuss your treatment options. Generally, he prefers to wait approximately 3-6 months to perform an enhancement to ensure that the final vision has been achieved.
As that point, either a hyperopia or myopia LASIK procedure will be performed to correct the residual error, if you and Dr. Cutarelli believe it is appropriate. This is typically accomplished by gently relifting the original LASIK flap rather than creating a new one.
Night or dim-light vision complications
Many LASIK patients notice a temporary decrease in vision at
night or in dim light with symptoms that include decreased contrast
sensitivity, glare, halos, and starbursts. The experience of these
phenomena can range from mild to severe.
These symptoms usually subside within a few days or weeks for the vast majority of patients who experience them. However, some will continue for a greater length of time and there may be a need to wear glasses to drive at night. These effects are most usually temporary, but could be permanent and uncorrectable.
There are several potential causes of decreased night vision. The most common is the normal mild swelling of the LASIK flap, which resolves within a few weeks of surgery.
Many researchers believe that patients who have pupils that exceed the ablation zone may be more likely to experience decreased night or low-light vision following LASIK than the general population. Another cause is incomplete correction of the nearsightedness, farsightedness or astigmatism; this is probably more significant than pupil size according to recent research performed by Dr. Steve Schallhorn at the Navy Medical Hospital. Clinical dry eye can also contribute to the experience of glare and halos.
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Decreased contrast sensitivity
Contrast sensitivity deals with a patient's ability to discern
images of varying shades from the background - in other words, how
faded an image can be before it is indistinguishable from the background.
Imagine driving in fog - the thicker the fog, the grayer all
objects become and the more difficult to distinguish their features.
Because contrast sensitivity is important to the quality of vision,
several studies have been conducted over the last several years to
determine the affect of LASIK on it.
· All noted a decrease in contrast sensitivity, which lasted from one to six months post-operatively.We have found two independent studies that note subjective reports of reduced night vision:· However, all but one also noted a return to pre-operative function by the six-month visit.
· The first assessed 174 eyes that were treated between November 1997 and October 1998. Of them, 29% reported reduced night vision - however, it's important to note that 97% of patients indicated they would decided to have LASIK again.Many improvements and technological advancements have been made since that time. The "Summary of Safety & Effectiveness Data" required by the United States FDA tabulates the subjective reporting of glare, halos and difficulty with nighttime driving pre-operatively and post-operatively at various time intervals.
· The second involved questionnaires sent to 50 patients; 8.8% reported difficulty with nighttime driving. Again, 98% noted overall satisfaction with their outcomes.
Overall, two reports noted improvement of nighttime vision as compared to the pre-operative assessment and one noted a split, with between 5-9% of patients noting a significant improvement and the same number noting the symptoms were significantly worse.
Using the latest technology with the VISX CustomVue Wavefront system, more patients were satisfied or very satisfied with their night vision without glasses or contacts after LASIK compared to their level of satisfaction with glasses or contacts before LASIK.
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Glare/halos/starbursts
Those patients who experience persistent glare, halos or starbursts
do have several treatment options, including prescription eye drops
to help constrict the pupil at night to reduce the symptoms of decreased
night vision.
This pharmaceutical approach is not successful for all people, and it also can represent a significant expense over time. Similarly, enhancement procedures may be an option, though not everyone is eligible for an additional procedure. Eligibility for enhancements depends on a number of factors that a doctor must evaluate.
Increased light sensitivity or fluctuating vision
Most patients are sensitive to light and glare or find that their
vision fluctuates after LASIK eye surgery. These conditions are generally
temporary and go away within three months after the procedure. However,
in a few cases they could be permanent.
Optical imbalance in eyes
If a surgeon performs laser eye surgery on one eye only, leaving
the other for later, the eyes may not be able to balance and focus
properly until the procedure is performed on the other eye.
