Lasik Eyes Surgery - PRK/LASIK nerve regeneration

Author

PRK/LASIK nerve regeneration

Ragnar

2006-01-09, 11:07 am

The important point made below is that the nerves regenerate
completely after refractive surgery. What isn't mentioned is that the
nerves recover enough after about 3 months so that they are not a
problem anymore.

BUT.. there is a problem with that post below...first off, it only
involved 12 PRK patients.. that is a bit small for a study.
The BIG problem is that it is comparing PRK with an average of -3.73
diopters of correction to LASIK with an average of -6.56 diopters of
correction!!!! Gee, I wonder if that makes a difference.

Also, there are three nerve bundles/trunks on the cornea. The are 120
degrees from each other, forming a triangle. If the flap was
completely removed (free cap) the initial nerve density would be
reduced 100%. A free cap is a mistake that takes a while to recover
from. When a LASIK FLAP is made, the initial nerve reduction is
either 33% or 66% depending upon which direction the surgeon decided
to make the flap. Obviously in the study below, all the flaps were
done cutting two of the three trunks resulting in 66% reduction after
surgery, 51% after one year.
Obviously, if the flap had been cut with only one trunk cut, the
initial loss would be 33% and would likely be 25% after a year.

So, forget the idea that PRK is better for the nerves than LASIK.

The question remains - why don't surgeons only cut one trunk instead
of two that they usually do? Because it's not a big deal! Also, the
standard 2 trunk cut results in a flap where gravity is working with
you in keeping the flap perfectly in place so that there is not a
bigger gap at the top of your flap.

Again the key point is that in both cases, those nerves regenerate to
pre-operative levels. End of story.
=====

By the way.. the nut posting about Aspartame is correct. Aspartame is
converted into tiny amounts of formaldehyde in the liver.
That fact is becoming more and more publicized since Splenda became
available.
Aspartame was the most scrutinized substance ever in the history of
the FDA, yet the FDA still approved it. So much for the FDA.

On Mon, 09 Jan 2006 05:09:04 GMT, Glenn - USAEyes.org
<glenn.hageleSTOPSPAM@USAEyes.org> wrote:

>The poster has now been published.
>
>~~~~~~~~~~~~~~~~~~
>
>AJO; Volume 140, Issue 6, Pages 1059-1064.e1 (December 2005)
>
>Recovery of Corneal Subbasal Nerve Density After PRK and LASIK
>Presented in part at the European Society of Cataract and Refractive
>Surgery, Paris, France, September 18-22, 2004, and at the Association
>for Research in Vision and Ophthalmology, Ft Lauderdale, Florida, May
>1-5, 2005.
>
>Jay C. Erie, MDa , Jay W. McLaren, PhDa, David O. Hodge, MSb,
>William M. Bourne, MD
>
>Purpose
>
>To measure and compare the return of corneal innervation up to 5 years
>after photorefractive keratectomy (PRK) and laser in situ
>keratomileusis (LASIK).
>Design
>
>Prospective, nonrandomized clinical trial.
>Methods
>
>Eighteen eyes of 12 patients received PRK to correct a mean refractive
>error of -3.73 ± 1.30 diopters, and 16 eyes of 11 patients received
>LASIK to correct a mean refractive error of -6.56 ± 2.44 diopters.
>Corneas were examined by confocal microscopy before and at 1, 2, 3,
>and 5 years after the procedures. Subbasal nerve fiber bundles were
>measured to determine density (visible length of nerve/frame area) and
>expressed as micrometers per square millimeters. Differences were
>compared by Friedman's test and adjusted for multiple comparisons by
>the Student-Newman-Keuls procedure.
>Results
>
>After PRK, mean subbasal nerve density was reduced by 59% at 1 year
>(2764 ± 1321 m/mm2 [±SD]) when compared with preoperative (6786 ± 1948
>m/mm2; P < .001). By 2 years, subbasal nerve density (6242 ± 1763
>m/mm2) was not significantly different from density before PRK and
>remained unchanged to 5 years (5903 ± 3086 m/mm2). After LASIK,
>subbasal nerve density was reduced by 51%, 35%, and 34% at 1, 2, and 3
>years, respectively (P < .001). By 5 years, subbasal nerves had
>returned to densities (4441 ± 2819 m/mm2) that were not significantly
>different from densities before LASIK (5589 ± 2436 m/mm2).
>Conclusion
>
>Corneal subbasal nerve density does not recover to near preoperative
>densities until 5 years after LASIK, as compared with 2 years after
>PRK.
>
>Glenn Hagele
>Executive Director
>USAEyes.org
>
>"Consider and Choose With Confidence"
>
>Email to glenn dot hagele at usaeyes dot org
>
>http://www.USAEyes.org
>http://www.ComplicatedEyes.org
>
>I am not a doctor.

Glenn - USAEyes.org

2006-01-09, 11:07 am

>BUT.. there is a problem with that post below...first off, it only
>involved 12 PRK patients.. that is a bit small for a study.

Although the cohort was relatively small, the results were universal.

Glenn Hagele
Executive Director
USAEyes.org

"Consider and Choose With Confidence"

Email to glenn dot hagele at usaeyes dot org

http://www.USAEyes.org
http://www.ComplicatedEyes.org

I am not a doctor.

axxx

2006-01-09, 12:56 pm

By 5 years, subbasal nerves had returned to densities (4441 =B1 2819
m/mm2) that were not significantly different from densities before
LASIK (5589 =B1 2436 m/mm2).

4441/5589=3D0.79
~80%
It is not "kills" .
But, patients should know it.

Ragnar

2006-01-10, 1:04 am

In your reply, you accidentally left out the part that the LASIK
ablations were about twice as deep due to treating twice the error.

You also left out that the LASIK flaps were cut using the direction
that severs 2 of the 3 nerve trunks. If the direction was nasal, then
only 1 trunk would have been severed or 33%.

Most importantly, you left out that in either surgery, the nerves
regenerate to their pre-operative state.

On Mon, 09 Jan 2006 15:27:23 GMT, Glenn - USAEyes.org
<glenn.hageleSTOPSPAM@USAEyes.org> wrote:

>
>Although the cohort was relatively small, the results were universal.
>
>Glenn Hagele
>Executive Director
>USAEyes.org
>
>"Consider and Choose With Confidence"
>
>Email to glenn dot hagele at usaeyes dot org
>
>http://www.USAEyes.org
>http://www.ComplicatedEyes.org
>
>I am not a doctor.