Post your questions and start your research in this forum if more than three months ago you had any type of surgery to reduce the need for glasses and contacts.


Postby DryEye » Wed May 02, 2007 5:13 pm

Is it correct to assume that people who measure very low high order aberrations (HOA's) prior to lasik will come out with higher HOA's - regardless of the laser that is used? Are the three causes of induced HOA's the way the flap is created, the laser itself and one's treatment zone?
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Postby LasikExpert » Wed May 02, 2007 7:19 pm

HOAs are a measurement of aberrations in the optics of the eye. As a general rule HOA are increased with all cornea-based refractive surgery, including Lasik, All-Laser Lasik, PRK, LASEK, and Epi-Lasik.

As a general rule HOA are increased more with conventional ablation than with wavefront-optimized ablation, and HOAs increase more with wavefront optimized ablation than with wavefront-guided ablation.

These are general rules and are not consistent with every patient.

The increase in HOA is not related to where the HOA's start. There is no evidence that someone with low natural HOA would have a greater increase in HOAs than someone starting with HOA closer to the norm, however the effect may be more noticeable.

People who have very low natural HOA before surgery tend to have corrected vision that is better than the norm. Due to this unusually excellent vision (as good as 20/10 for some), any degradation in vision quality may be very noticeable. The patient may be 20/20 after Lasik, but if you were 20/10 that is a step down.

This is yet another reason why a comprehensive evaluation by a competitent doctor is so important.
Glenn Hagele
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Lasik Doctor Certification

I am not a doctor.
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Postby peakaboo » Fri May 11, 2007 3:30 am

My surgeon explained HOAs today...basically, pre-surgery the percentage of HOAs vs. LOAs is very low for people who have poor vision. This is because most of the visual problems are due to myopia or astigmatism.

After successful lasik surgery, your eyes are going to be very close to plano, making LOAs a much smaller percentage of residual acuity problems. If after surgery you're still not seeing perfect, the majority of any further corrective procedures will be aimed at correcting the HOAs because they will comprise the majority of the residual defects.

The surgeon explained that the amount of ablation required for enhancements aimed at reducing residual HOAs is almost negligable compared to the original ablation to correct the LOAs. My enhancement would only require about another 10 microns of tissue to be removed, and only in those places where the wavefront mapping indicates HOAs may be causing a problem, whereas I had over 100 microns removed during the initial procedure. Flap thickness was 110 microns, leaving me with about 305 uM left of untouched stromal bed tissue.
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