Overcorrection is when
refractive surgery such as conventional or custom
wavefront
Lasik,
All-Laser Lasik,
PRK,
LASEK,
Epi-Lasik,
CK,
RLE, or
P-IOL, has changed the
refractive errorr 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 Surgery 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, All-Laser
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.
Overcorrection for CK Regression
CK is considered a temporary correction because CK regresses
over a period of years until all induced changes have dissipated.
Because of full regression, deliberate minor overcorrection may
be desired to maintain vision advantages for a longer period of
time. For more details see
CK Information
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, All-Laser Lasik, PRK, LASEK, or Eip-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, All-Laser Lasik, PRK,
LASEK, or Epi-Lasik to "fine tune" the correction. See
Refractive Lens Exchange Information or
Phakic Intraocular Lens Information
If you are ready to choose a doctor to be evaluated for conventional
or custom
wavefront
Lasik,
All-Laser Lasik,
PRK,
LASEK,
Epi-Lasik,
NearVision CK,
RLE, or any
refractive surgery procedure, we highly recommend you consider
a doctor who has been evaluated and certified by the USAEyes
nonprofit organization. Locate a USAEyes Evaluated & Certified
Lasik Laser Eye Surgery Doctor.
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