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Overcorrection is when refractive surgery such as conventional or custom wavefront Lasik, Bladeless Lasik, PRK, LASEK, Epi-Lasik, RLE, or P-IOL, has changed the refractive error more than desired.
If an overcorrected patient was myopic (nearsighted, shortsighted) before surgery and the target
was plano (no refractive error), then the patient would now be hyperopic (farsighted, longsighted). If the patient was hyperopic,
the patient would be myopic if overcorrected. Overcorrection is
normally undesired and unexpected, however in some instances overcorrection
may be planned.
Overcorrection For Monovision
Overcorrection may be desired if the patient seeks monovision correction and was originally hyperopic. Monovision
is generally when one eye is made myopic for near vision and the
other eye is plano for distance vision. Monovision can be attained
with contact lenses or refractive surgery. In this circumstance,
the hyperopic patient would deliberately have one eye overcorrected
into myopia to attain the monovision effect. If the patient is myopic
before surgery, either no correction will be attempted in one eye,
or the eye for near vision will be undercorrected. For details read Monovision information.
Overcorrection for Expected Regression
Deliberate overcorrection may be used to resolve expected regression.
The cornea tends to regress back toward the original refractive
error after cornea-based refractive surgery procedures Lasik, Bladeless
Lasik, PRK, LASEK, Epi-Lasik and CK. During healing, both the epithelium and the deeper stroma can reshape and reform at different rates, which may
cause regression. This occurs mostly in myopic patients who have
more than 6.0 diopters of refractive error and virtually all hyperopic patients. Depending
upon the individual circumstances and the technique used for correction,
hyperopic patients tend to regress significantly. For details read Lasik Regression information.
The patient may be deliberately overcorrected with the expectation
that regression will bring the patient back to the desired correction.
Conventional vs. Custom Wavefront-Guided Ablation
There may be some difference in regression rates between conventional
and custom wavefront-guided excimer laser ablations. Wavefront-guided
ablations tend to remove more tissue to achieve the same refractive
change than conventional ablations. A greater amount of tissue removal
may cause more regression if the patient requires a large amount
of change. A doctor may slightly induce overcorrection to accommodate
expected regression due to a deep ablation necessary for wavefront-guided
ablation.
Overcorrection with Custom Wavefront-Guided Ablation
Anecdotal information indicates that individuals with very low
(less than about 2.00 diopters) myopia tend to be overcorrected
when wavefront-guided ablation is used. Also, if the wavefront aberrometer
is not able to gain a clear evaluation of the patient's optics,
overcorrection may occur. Laser manufacturers are responding to
this situation with new algorithms for the computer that guides the laser, and doctors
develop customized nomograms based upon prior experience. See Custom Wavefront Ablation
Overcorrection with Lens-Based Techniques RLE and P-IOLs
Overcorrection with the lens-based techniques RLE and P-IOLs
is very different than overcorrection with a cornea-based technique
like Lasik, Bladeless Lasik, PRK, LASEK, or Epi-Lasik. After the
healing period, RLE and P-IOL do not regress and the overcorrection
is permanent. Except for monovision purposes, lens-based overcorrection
means that the calculations used to determine the required lens
power were not correct.
The response to lens-based overcorrection tends to be the use
of glasses or contact lenses, removal of the implanted lens and
replacement with a new lens of a different power, or the use of
a cornea-based surgery technique like Lasik, Bladeless Lasik, PRK,
LASEK, or Epi-Lasik to "fine tune" the correction.
Looking For Best Lasik Surgeon?
If you are ready to choose a doctor to be evaluated for conventional
or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization.
Locate a USAEyes Evaluated & Certified Lasik Doctor.
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