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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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