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Home > Archive > Lasik Eyes Surgery > November 2004 > 3 years post-lasik, corneal nerves at only 60% of pre-lasik density
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3 years post-lasik, corneal nerves at only 60% of pre-lasik density
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| Sandy 2004-11-03, 11:10 am |
| Want dry eyes? Have lasik!
http://www.iovs.org/cgi/content/abstract/45/11/3991
Corneal Reinnervation after LASIK: Prospective 3-Year Longitudinal
Study
Martha P. Calvillo,1 Jay W. McLaren,1 David O. Hodge,2 and William M.
Bourne1
1From the Departments of Ophthalmology and 2Biostatistics, Mayo Clinic
College of Medicine, Rochester, Minnesota.
PURPOSE. To measure the return of innervation to the cornea during 3
years after LASIK.
METHODS. Seventeen corneas of 11 patients who had undergone LASIK to
correct myopia from –2.0 D to –11.0 D were examined by confocal
microscopy before surgery, and at 1, 3, 6, 12, 24, and 36 months after
surgery. In all available scans, the number of nerve fiber bundles and
their density (visible length of nerve per frame area), orientation
(mean angle), and depth in the cornea were measured.
RESULTS. The number and density of subbasal nerves decreased >90% in
the first month after LASIK. By 6 months these nerves began to
recover, and by 2 years they reached densities not significantly
different from those before LASIK. Between 2 and 3 years they
decreased again, so that at 3 years the numbers remained <60% of the
pre-LASIK numbers (P < 0.001). In the stromal flap most nerve fiber
bundles were also lost after LASIK, and these began recovering by the
third month, but by the third year they did not reach their original
numbers (P < 0.001). In the stromal bed (posterior to the LASIK flap
interface), there were no significant changes in nerve number or
density. As the subbasal nerves returned, their mean orientation did
not change from the predominantly vertical orientation before LASIK.
Nerve orientation in the stromal flap and the stromal bed also did not
change.
CONCLUSIONS. Both subbasal and stromal corneal nerves in LASIK flaps
recover slowly and do not return to preoperative densities by 3 years
after LASIK. The numbers of subbasal nerves appear to decrease between
2 and 3 years after LASIK. The orientation of the regenerated subbasal
nerves remains predominantly vertical.
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| In article <1f704412.0411030834.1df0a0d1@posting.google.com>,
sandy@savvysneaks.com (Sandy) wrote:
> Want dry eyes? Have lasik!
Come on Sandy. Who want dry eyes? Nobody has LASIK to get dry eye.
Unfortunately in a small number of cases some people continue to
experience dry eyes beyond the normal healing period, but most do not.
Where does this study talk about dry eyes anyway?
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| Glenn - USAEyes.org 2004-11-03, 7:12 pm |
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>Where does this study talk about dry eyes anyway?
What Sandy is probably referencing is that most doctors assume that
cutting the corneal nerves during LASIK contributes to dry eye by
disrupting the normal flow of information to the tearing system so it
knows when to turn on, when to blink, etc.
What is important to note is that while corneal density takes a long
time to return to pre-LASIK levels, corneal sensitivity does not
normally take anywhere near this much time. For those who do
experience dry eyes, the symptoms typically last only a few days or
weeks.
Long-term LASIK related dry eye is the complaint we find most
prevalent in our patient outcomes analysis. In fact, nearly every
other LASIK related complication has diminished even to the point of
disappearing altogether, except dry eye.
Doctors believe that a nasal hinge on the LASIK flap may limit corneal
desensitizing because a nasal hinge does not sever one of the main
nerve trunks within the cornea, whereas a superior hinged flap does.
A thinner LASIK flap also seems to be less disruptive, but thinner
flaps can be problematic unless the surgeon uses a femtosecond laser
for flap creation. Even then, these techniques are not consistently
reducing or eliminating LASIK induced dry eye.
PRK does seem to have a significantly lower incidence of dry eye, but
dry eye is not totally eliminated as a possibility.
If a patient has uncontrolled pre-existing dry eye problems, then
LASIK may not be wise, PRK may be better, lens-based surgery might be
appropriate, and glasses are probably going to be the best.
We have a detailed article on dry eye at
http://www.complicatedeyes.org/dry_eye_treatment.htm
Glenn Hagele
Executive Director
Council for Refractive Surgery Quality Assurance
Email to glenn dot hagele at usaeyes dot org
http://www.USAEyes.org
http://www.ComplicatedEyes.org
I am not a doctor.
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