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B. Meghpara, H. Nakamura, G. Vemuganti, S. Murthy, B. Y. J. T. Yue, D. P. Edward; Histopathological and Immunohistochemical Studies of Keratoglobus. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4315. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To examine histopathological and immunohistochemical features of keratoglobus. Keratoglobus is a rare congenital or acquired disease characterized by diffuse corneal thinning and a globular corneal contour. The thinning is often more pronounced in the peripheral than the central cornea.
Eleven corneal buttons were obtained at the time of penetrating keratoplasty from patients with keratoglobus. Their histological features were examined by hematoxylin and eosin (H&E) staining using paraffin-embedded sections. Immunohistochemical staining for α1-proteinase inhibitor (α1-PI), Sp1, MMP1, MMP2, and MMP3 was performed with two normal and two keratoconus corneal sections as controls.
H&E staining revealed central and peripheral thinning of the cornea in all keratoglobus specimens. Stromal thickness in the periphery (214 ± 78 µm) was thinner than that in the center (246 ± 86 µm, p<0.05, Wilcoxon signed-rank test). Diffuse and/or focal Bowman’s layer disruption was observed in eight keratoglobus specimens. Central mononuclear cell and fibroblast infiltration along with central neovascularization was detected in two specimens. Immunostaining for α1-PI showed a lower staining intensity in both keratoglobus and keratoconus than in normal controls. Positive nuclear staining for Sp1 in the corneal epithelium was obtained in the keratoglobus (9/11) and the keratoconus (2/2), but not in the normal corneas. For MMP1, MMP2 and MMP3, moderate staining was seen in the keratoglobus corneas. Weak staining was observed in keratoconus, and staining was nearly absent in normal controls. In the keratoglobus cornea, peripheral epithelial immunostaining was more intense compared to its central counterpart. More specifically, staining has highest in the basal layer where the underlying Bowman’s layer was disrupted.
Histological features in the keratoglobus cornea are consistent with previous reports. A reduction in α1-PI and an increase in Sp1, typically seen in keratoconus, were detected immunohistochemically in keratoglobus, especially in areas with Bowman’s layer disruption. This suggests that keratoglobus may have biochemical abnormalities similar to that in keratoconus.
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