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    Histological findings in a failed corneal riboflavin-UVA collagen cross-linking performed for progressive keratoconus

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    Purpose: 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. Methods: The excised cornea was formalin-fixed, paraffin-embedded, and examined microscopically. Deparaffinized 4-mu m sections were stained with hematoxylin-eosin and Masson trichrome. Further tissue sections were subjected to immunohistochemical evaluation of CD34 and Ki-67 antigens. Results: 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. Conclusions: 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

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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