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      Profile of Microbial Keratitis after Corneal Collagen Cross-Linking

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          Abstract

          Purpose. To report the profile of microbial keratitis occurring after corneal collagen cross-linking (CXL) in keratoconus patients. Methods. A retrospective analysis of 2350 patients (1715 conventional CXL, 310 transepithelial CXL, and 325 accelerated CXL) over 7 years (from January 2007 to January 2014) of progressive keratoconus, who underwent CXL at a tertiary eye care centre, was performed. Clinical findings, treatment, and course of disease of four eyes that developed postprocedural moxifloxacin resistant Staphylococcus aureus (MXRSA) infectious keratitis are highlighted. Results. Four eyes that underwent CXL (0.0017%) had corneal infiltrates. All eyes that developed keratitis had conventional CXL. Corneal infiltrates were noted on the third postoperative day. Gram's stain as well as culture reported MXRSA as the causative agent in all cases. Polymerase chain reaction (PCR) in each case was positive for eubacterial genome. All patients were treated with fortified antibiotic eye drops, following which keratitis resolved over a 6-week period with scarring. All these patients were on long-term preoperative oral/topical steroids for chronic disorders (chronic vernal keratoconjunctivitis, bronchial asthma, and chronic eczema). Conclusion. The incidence of infectious keratitis after CXL is a rare complication (0.0017%). MXRSA is a potential organism for causing post-CXL keratitis and should be identified early and treated aggressively with fortified antibiotics.

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          Stress-strain measurements of human and porcine corneas after riboflavin-ultraviolet-A-induced cross-linking.

          To evaluate the biomechanical effect of combined riboflavin-ultraviolet A (UVA) treatment on porcine and human corneas. Department of Ophthalmology, Technical University of Dresden, Dresden, Germany. Corneal strips from 5 human enucleated eyes and 20 porcine cadaver corneas were treated with the photosensitizer riboflavin and irradiated with 2 double UVA diodes (370 nm, irradiance = 3 mW/cm2) for 30 minutes. After cross-linking, static stress-strain measurements of the treated and untreated corneas were performed using a microcomputer-controlled biomaterial tester with a prestress of 5 x 10(3) Pa. There was a significant increase in corneal rigidity after cross-linking, indicated by a rise in stress in treated porcine corneas (by 71.9%) and human corneas (by 328.9%) and in Young's modulus by the factor 1.8 in porcine corneas and 4.5 in human corneas. The mean central corneal thickness was 850 microm +/- 70 (SD) in porcine corneas and 550 +/- 40 microm in human corneas. Riboflavin-UVA-induced collagen cross-linking led to an increase in mechanical rigidity in porcine corneas and an even greater increase in human corneas. As collagen cross-linking is maximal in the anterior 300 microm of the cornea, the greater stiffening effect in human corneas can be explained by the relatively larger portion of the cornea being cross-linked in the overall thinner human cornea.
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            Induction of cross-links in corneal tissue.

            The aim of this study was to investigate the possibility of induction of cross-links in corneal tissue in order to increase the stiffness as a basis for a future conservative treatment of keratectasia. Collagenous biomaterials can be stabilized by chemical and physical agents. The epithelium of enucleated porcine eyes was removed. Eight test groups, 10 eyes each, were treated with UV-light (lambda=254 nm), 0.5% riboflavin, 0.5% riboflavin and UV-light (365 nm) blue light (436 nm) and sunlight, and the chemical agents-glutaraldehyde (1% and 0.1%, 10 min) and Karnovsky's solution (0.1%, 10 min). Strips of 5 mm in width and 9 mm in length were cut from each cornea and the stress-strain behaviour of the strips was measured to assess the cross-linking process. For comparison, ten untreated corneas were measured by the same method. Compared to untreated corneas treatment with riboflavin and UV-irradiation as well as weak glutaraldehyde or Karnovsky's solutions resulted in an increased stiffness of the cornea. The biomechanical behaviour of the cornea can be altered by glutaraldehyde, Karnovsky's solution, and with riboflavin and UV-irradiation which offers the potential of a conservative treatment of keratoconus. To optimize this effect further investigation is necessary regarding the dose-response and in-vivo application. Copyright 1998 Academic Press Limited.
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              Epithelial injury induces keratocyte apoptosis: hypothesized role for the interleukin-1 system in the modulation of corneal tissue organization and wound healing.

              The purpose of this study was to determine the role of programmed cell death (apoptosis) in the disappearance of keratocytes beneath an epithelial debridement wound in the cornea and to investigate a potential role of interleukin-1 (IL-1) in induction of apoptosis in stromal fibroblasts in vitro and keratocytes in vivo. Keratocyte and stromal fibroblast cell morphology was examined in wounded and unwounded mouse corneas using transmission electron microscopy. Nuclear DNA fragmentation was detected with the TUNEL assay for 3'-hydroxyl DNA ends. The effect of IL-1 on keratocytes in vivo was determined by microinjection of IL-1 alpha into the central corneal stroma via a limbal entry site. The in vitro effects of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) were determined with primary cultures of human corneal stromal and dermal fibroblasts. Cell shrinkage, blebbing with formation of membrane bound bodies, condensation and fragmentation of the chromatin, and DNA fragmentation, consistent with apoptosis were detected in anterior stromal keratocytes after epithelial scrape wounds. Thus, disappearance of keratocytes from the underlying stroma following epithelial debridement is mediated by apoptosis. Microinjection of IL-1 alpha into the central stroma of the mouse cornea caused a redistribution of keratocytes in the stroma via apoptosis and, possibly, negative chemotaxis. IL-1 alpha and IL-1 beta induced apoptosis in corneal stromal and dermal fibroblasts in vitro. The epithelial/endothelial-stromal IL-1 system may mediate corneal tissue organization and responses to mechanical- and pathogen-induced injury through induction of keratocyte apoptosis. Keratocyte apoptosis is likely an initiating event in wound healing following corneal surgery. We hypothesize that derangement's in this system may have a role in the pathogenesis of keratoconus and other diseases of the cornea.
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                Author and article information

                Journal
                Biomed Res Int
                Biomed Res Int
                BMRI
                BioMed Research International
                Hindawi Publishing Corporation
                2314-6133
                2314-6141
                2014
                11 September 2014
                : 2014
                : 340509
                Affiliations
                1Narayana Nethralaya Eye Hospital Bangalore, Narayana Nethralaya 121/C, Chord Road, 1st “R” Block, Rajajinagar, Bangalore, Karnataka 560 010, India
                2Department of Ophthalmology, University Hospital Maastricht, P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands
                Author notes

                Academic Editor: George Asimellis

                Article
                10.1155/2014/340509
                4180902
                25302296
                3c23e147-fe26-43b5-bfae-31d854590bd4
                Copyright © 2014 Rohit Shetty et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 7 June 2014
                : 25 August 2014
                Categories
                Clinical Study

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