LASIK induces minimal regrowth and no haze development in rabbit corneas

To quantify central corneal regrowth and haze development after LASIK in rabbits.

New Zealand White rabbits received an 89 microm (-8 diopters) myopic LASIK and were evaluated during 4 months using slit-lamp and in vivo confocal microscopy to monitor changes in central corneal morphology, epithelial and stromal thickness, flap and bed thickness, and corneal light backscattering (haze). At various time-points, corneas were processed for histology.

Using in vivo confocal microscopy, LASIK induced no detectable morphological changes besides a slightly elevated light backscattering at the interface. Correspondingly, all corneas remained clear with no haze development by slit-lamp biomicroscopy. Corneal thickness was stable by 8 weeks after an increase of 17 +/- 4 microm that consisted of a 13 +/- 3 microm stromal regrowth and a 4 +/- 2 microm epithelial hyperplasia. At the LASIK interface, less than 4 microm new extracellular matrix was deposited. Accordingly, all LASIK flaps were easily pulled off by 6 months.

LASIK induces a minimal wound healing response in rabbit corneas with no haze development and a regrowth (regression) of only 17 microm of an 89-microm photoablation. Three main factors contributed to the observed regrowth: epithelial hyperplasia (approximately 4 microm), matrix deposition at the LASIK interface (approximately 4 microm), and stromal growth outside the interface within the flap and wound bed (approximately 9 microm).