Histopathologic and immunohistochemical studies of keratoglobus

Objective: To examine histopathologic and immunohistochemical features of human corneal buttons from patients who developed keratoglobus. Methods: Nine corneal buttons were obtained during penetrating keratoplasty from patients with keratoglobus. Histologic features were examined using hematoxylin-eosin-stained sections. Immunohistochemical staining for α1-proteinase inhibitor, Sp1, and matrix metalloproteinases 1, 2, and 3 was performed, with 2 normal and 2 corneal sections with keratoconus as controls. Results: Hematoxylin-eosin staining revealed diffuse stromal thinning and focal disruptions in Bowman's layer in all keratoglobus specimens. Similar abnormal immunostaining results for α1-proteinase inhibitor and Sp1 were detected in keratoglobus and keratoconus at their respective active disease sites. Immunostaining for matrix metalloproteinases 1, 2, and 3 was significantly more intense in corneas with keratoglobus than in normal controls. Matrix metalloproteinase staining intensity was especially prominent in areas where the underlying Bowman's layer was disrupted. Conclusions: Histological features in our keratoglobus specimens are consistent with previous reports. The similarities in immunohistochemical labeling between keratoglobus and keratoconus suggest that these entities may share common mechanisms that are involved in stromal thinning.