To report the histological and immunohistochemical findings in a cornea removed from a patient who had undergone collagen cross-linking (CXL) with riboflavin and ultraviolet-A for progressive keratoconus. CXL was performed following the Siena protocol. Two years post-CXL, a visual acuity impairment in the treated eye secondary to corneal stromal opacity had occurred, together with corneal thinning and flattening.
The excised cornea was formalin-fixed, paraffin-embedded, and examined microscopically. Deparaffinized 4-μm sections were stained with hematoxylin–eosin and Masson trichrome. Further tissue sections were subjected to immunohistochemical evaluation of CD34 and Ki-67 antigens.
Histologically, there was no scar tissue in the failed cornea. The biomicroscopic stromal opacity corresponded microscopically to an acellular area, devoid of keratocytes, and to compaction of the lamellar collagen. Amorphous, weakly eosinophilic interlamellar deposits, extending from the anterior to the posterior two thirds of the stroma, were noted.
CXL is a promising procedure for the treatment of progressive keratoconus with minimal reported side effects. In the present case, we speculate that the short corneal soaking time (15 minutes according to the Siena protocol) may have resulted in inefficient ultraviolet-A blocking, thermal injury, and deeper keratocyte death. Inadequate keratocyte stem cells reservoir could also play a role in individual cases.
*Department of Experimental Medicine and Pathology, First Faculty of Medicine, University of Rome “Sapienza,” Rome, Italy
†Department of Ophthalmic Science, Second Faculty of Medicine, University of Rome “Sapienza,” Rome, Italy
‡Fabia Mater Hospital, Roma, Italy
§Department of Ophthalmic Science, First Faculty of Medicine, University of Rome “La Sapienza,” Rome, Italy.
Reprints: Irene Pecorella, Department of Experimental Medicine and Pathology, University of Rome “Sapienza,” Viale Regina Elena 324, Rome 00161, Italy (e-mail: email@example.com).
The authors state that they have no financial or conflicts of interest to disclose.
Received March 8, 2012
Accepted March 10, 2012