Overexpression of MMP-1 and MMP-3, a phenotype previously linked with UV exposure in dermal fibroblasts to explain the pathologic finding of elastotic degeneration, suggests that pterygium head fibroblasts might be intrinsically altered by UV, which might be responsible for corneal invasion.
SPARC was upregulated in pterygium and may collaborate with increased MMP-3 in some patients to account for many of the phenotypic properties characteristic of pterygium.