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Overcorrection - Unexpected, Unwanted, Desired, and Planned

Relation with Lasik, Bladeless Lasik, PRK, LASEK, Epi-Lasik, RLE, and P-IOL overcorrection.

Image of woman holding magnifying glass to one eye causing the eye to appear large.  
Overcorrection is when the targeted correction is missed, sometimes deliberately.  

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.

Personalized Answers

If this article did not fully answer your questions, use our free Ask Lasik Expert patient forum.

Recent Lasik Overcorrection Medical Journal Articles...

Related Articles

Aspheric Ablation Depth as the Target Depth for Enhanced Wavefront-Guided Myopic Retreatments After Laser-Assisted In Situ Keratomileusis.

Cornea. 2015 Oct 19;

Authors: Hsu YR, Shen EP, Hsieh YT, Chang HW, Hu FR

PURPOSE: To propose a new adjustment method and present the clinical result of wavefront-guided myopic laser-assisted in situ keratomileusis (LASIK) retreatment with an aspheric program-targeted central ablation depth to avoid refractive overcorrection.
METHODS: Thirty-two eyes (of 20 consecutive patients) that underwent wavefront-guided LASIK myopic retreatment between January 2009 and February 2012 after primary wavefront-guided LASIK for myopia were included. Wavefront-guided retreatments were performed using the Bausch and Lomb Technolas 217z100 excimer laser system. Wavefront-guided retreatments were adjusted by setting the ablation depth corresponding to the ablation depth determined by the aspheric program. The refractive outcome, visual outcome, and outcome of high-order aberrations (HOAs) were analyzed. Linear mixed models were also used to evaluate the predicting factors for retreatment offset.
RESULTS: Mean age was 29.5 ± 3.1 years. Spherical equivalent (SE) before retreatment was -1.0 ± 0.44 diopters (D) (range, -2.25 to -0.5). Twelve months postoperatively, SE was -0.03 ± 0.12 D, and 31 of 32 eyes had an uncorrected visual acuity 20/20 or better. All eyes were within ±0.5 D. None of the eyes had lost >2 lines of Snellen visual acuity. Safety and efficacy indices were 1.03 and 1.00, respectively. Total HOA, coma, and trefoil were reduced significantly (P = 0.028, P = 0.036, P = 0.034, respectively). Predictive factors for the amount of offset required are significantly related to preoperative SE (P = 0.006) and spherical aberration (P = 0.03, adjusted by SE).
CONCLUSIONS: Setting the target ablation depth using the aspheric program provided high refractive predictability with a satisfactory visual outcome, significant reduction of HOAs, and no overcorrections.

PMID: 26488625 [PubMed - as supplied by publisher]


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