Abstract
Purpose::
To investigate long term changes in corneal wound healing following laser in situ keratomileusis (LASIK) using routine light and confocal scanning laser microscopy.
Methods::
Thirteen human eye bank corneas from 13 donors (mean±SD: 53.0±9.2 yrs; range 30-70 yrs) with previous LASIK (mean±SD: 4.1±1.9 yrs; range 0.75-7.0 yrs post-op) were studied. Tissue samples were bisected, formalin-fixed and embedded in paraffin according to standard protocols. Six microns thick sections were cut, stained for hematoxylin and eosin (H&E), and periodic acid Schiff (PAS), or were incubated with monoclonal anti-human cellular fibronectin (FN) IgG1 antibody or biotinylated hyaluronic acid binding protein (HABP). Immunoreactivity was detected using FITC conjugated goat anti-mouse IgG (FN) or avidin-horseradish-peroxidase method (HABP). Sections were evaluated for histopathologic and immunohistologic findings at the peripheral (flap margin) and central/paracentral LASIK interface wound by light and confocal scanning laser microscopy.
Results::
LASIK corneas showed 3 histopathologic types of corneal wound healing: epithelial cell modifications (basal cell hypertrophy, hyperplasia), production of a hypercellular fibrotic (flap margin) and a hypocellular primitive stromal scar (central/paracentral interface). LASIK flap thickness measured on average 133.8±15.0µm (range 120 to 160µm). Immunohistochemistry revealed FN in the hypercellular peripheral scar (n=10; flap margin) up to 7 years post-LASIK. A faint signal (FN) was also detected in the central/paracentral interface wound (n=4) in LASIK corneas with thin flaps (≤120µm). Immunostaining for HA was positive at the corneal endothelium and occasionally in subepithelial areas at the flap margin, but negative in the LASIK interface wound and corneal stroma.
Conclusions::
Corneal injury following LASIK results in formation of a hypercellular, fibrotic (flap margin) and a hypocellular, primitive scar(central/paracentral interface). Long-lasting expression of extracellular matrix proteins usually involved in corneal wound healing (i.e. fibronectin) appears to reflect a highly coordinated, bi-directional communication between corneal epithelial cells and stromal keratocytes and may contribute to a more pronounced wound healing response at the LASIK flap margin.
Keywords: wound healing • cytokines/chemokines • refractive surgery: LASIK