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B. Meghpara, H. Nakamura, M. Macsai, J. Sugar, A. Hidayat, B. Y. J. T. Yue, D. P. Edward; Histopathological and Immunoistochemical Studies of Keratectasia Following Laser in situ Keratomileusis (LASIK). Invest. Ophthalmol. Vis. Sci. 2007;48(13):5317.
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© ARVO (1962-2015); The Authors (2016-present)
Iatrogenic keratectasia is a serious complication following laser in situ keratomileusis (LASIK), and its clinical features are similar to keratoconus. In this study, we examined histopathological and immunohistochemical features of post-LASIK keratectasia.
Four corneal buttons were obtained at the time of penetrating keratoplasty from patients who developed keratectasia after LASIK. Their histological features were examined by hematoxylin and eosin (H&E) staining using paraffin-embedded sections, and by electron microscopy. Immunohistochemistry for α1-proteinase inhibitor (α1-PI), Sp1, MMP1, MMP2, and MMP3 was performed. Normal and keratoconus corneas (n=2) were used as controls.
Stromal thinning of the central cornea was observed after H&E staining for all keratectasia corneas. Flap and stromal bed thickness were 78 ± 18.7 and 191 ± 73.5 µm, respectively. No histological features specific to keratoconus, including Bowman’s layer disruption, were identified in keratectasia. By electron microscopy, collagen fibril thinning was observed, while inter-fibril distance was within normal range (collagen fibril diameter: 22.6 ± 1.5 nm, inter-fibril distance: 10.0 ± 9.6 nm). Immunostaining for α1-PI showed higher intensity in keratectasia than in keratoconus corneas. Sp1 staining was absent or very weak in keratectasia, whereas it was moderate in keratoconus. The staining intensity and/or pattern for α1-PI and Sp1 in keratectasia was in fact comparable to that seen in normal corneas. No significant staining for MMP1, MMP2, and MMP3 was observed in either keratectasia or normal corneas.
Histological findings suggest that the post-LASIK keratectasia is caused by thinning of corneal stromal fibers. Discrepant results between keratectasia and keratoconus suggest that the pathogenesis in the post-LASIK keratectasia is different from that in keratoconus.
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