Epithelial growth over the optic surface of the type I Boston Keratoprosthesis: Histopathology and implications for biointegration

Moran Eye Center, University of Utah, Salt Lake City, UT, USA.
Clinical Ophthalmology (Impact Factor: 0.76). 10/2010; 4(1):1069-71. DOI: 10.2147/OPTH.S12780
Source: PubMed


We report the histopathology of epithelial overgrowth in the Boston type I keratoprosthesis. The epithelium shows an inconsistent number of layers and basement membrane and goblet cells are absent. Epithelialization of the keratoprosthesis optic would have multiple advantages, but the limitation of vision makes tolerating the overgrowth difficult.

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    • "Two recent case reports have described epithelial tissue, instead of stopping at the edge of the front plate, extending over the edge of the front plate and for a variable distance onto the anterior surface of the front plate in eyes implanted with more recent models of the Boston type I keratoprosthesis.22,23 The tissue was confirmed to be epithelium by light microscopic and immunohistochemical analysis. "
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    ABSTRACT: The purpose of this study was to assess whether the resolution offered by two different, recently commercially available high-resolution, spectral-domain anterior segment optical coherence tomography (AS-OCT) instruments allows for detailed anatomic characterization of the critical device-donor cornea interface in eyes implanted with the Boston type I permanent keratoprosthesis. Eighteen eyes of 17 patients implanted with the Boston type I keratoprosthesis were included in this retrospective case series. All eyes were quantitatively evaluated using the Cirrus HD-OCT while a subset (five eyes) was also qualitatively imaged using the Spectralis Anterior Segment Module. Images from these instruments were analyzed for evidence of epithelial migration onto the anterior surface of the keratoprosthesis front plate, and presence of a vertical gap between the posterior surface of the front plate and the underlying carrier donor corneal tissue. Quantitative data was obtained utilizing the caliper function on the Cirrus HD-OCT. The mean duration between AS-OCT imaging and keratoprosthesis placement was 29 months. As assessed by the Cirrus HD-OCT, 83% of eyes exhibited epithelial migration over the edge of the front plate. Fifty-six percent of the keratoprosthesis devices displayed good apposition of the device with the carrier corneal donor tissue. When a vertical gap was present (44% of eyes), the mean gap was 40 (range 8-104) microns. The Spectralis Anterior Segment Module also displayed sufficient resolution to allow for similar characterization of the device-donor cornea interface. Spectral-domain AS-OCT permits high resolution imaging of the keratoprosthesis device-donor cornea interface. Both the Cirrus HD-OCT and the Spectralis Anterior Segment module allowed for visualization of epithelial coverage of the device-donor cornea interface, as well as identification of physical gaps. These imaging modalities, by yielding information in regard to integration of the keratoprosthesis with surrounding corneal tissue, may help identify those at risk for keratoprosthesis-related complications, such as extrusion and endophthalmitis, and hence guide clinical management.
    Preview · Article · Aug 2012 · Clinical Ophthalmology
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    • "It has generally been assumed that epithelium does not grow over the plastic front plate of the keratoprosthesis, leaving the junction between the carrier donor corneal button and the keratoprosthesis front plate uncovered by epithelium. Recently, a case of epithelialization of the anterior surface of the keratoprosthesis front plate was reported [15]. Histopathologic analysis in this case demonstrated multilayered, non-keratinized squamous epithelial tissue, presumably of corneal epithelial origin. "
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    ABSTRACT: The aim of this work is to characterize a transparent tissue layer partially covering the anterior surface of the type I Boston permanent keratoprosthesis front plate in four patients. The tissue over the front plate was easily scrolled back as a single transparent layer using a sponge. In two cases, histopathologic analysis was undertaken and immunofluorescent staining with a cytokeratin 3-specific antibody was performed. The relationship of the tissue to the keratoprosthesis device was further characterized using spectral domain high-definition optical coherence tomography (HD-OCT). Histopathologic analysis revealed the tissue to be non-keratinized squamous epithelium. No goblet cells were seen, suggesting the cells were of corneal, and not conjunctival, epithelial origin. Immunofluorescent staining of all cells was positive for cytokeratin 3, a protein strongly associated with corneal epithelium. The tissue was easily discerned by HD-OCT and was of substantial thickness near the external junction between the keratoprosthesis device and the carrier corneal tissue. In three cases, visual acuity was unaffected by the presence or absence of this tissue. In one case, a prominent tissue margin temporarily obscured the visual axis and reduced visual acuity; this resolved with mechanical central debridement and has not recurred. The transparent tissue layer covering the anterior surface of the type I Boston keratoprosthesis front plate was found to represent non-keratinized squamous epithelium, most likely of corneal epithelial origin. This potentially represents a further step in bio-integration of the keratoprosthesis device. In particular, epithelial coverage of the critical junction between the device and the carrier corneal tissue might serve an important barrier function and further reduce the incidence of infection and extrusion of the type I Boston permanent keratoprosthesis.
    Full-text · Article · Feb 2012 · Albrecht von Graæes Archiv für Ophthalmologie
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    ABSTRACT: The biocompatibility and antibacterial properties of N,N-hexyl,methyl-polyethylenimine (HMPEI) covalently attached to the Boston Keratoprosthesis (B-KPro) materials was evaluated. By means of confocal and electron microscopies, we observed that HMPEI-derivatized materials exert an inhibitory effect on biofilm formation by Staphylococcus aureus clinical isolates, as compared to the parent poly(methyl methacrylate) (PMMA) and titanium. There was no additional corneal epithelial cell cytotoxicity of HMPEI-coated PMMA compared to that of control PMMA in tissue cultures in vitro. Likewise, no toxicity or adverse reactivity was detected with HMPEI-derivatized PMMA or titanium compared to those of the control materials after intrastromal or anterior chamber implantation in rabbits in vivo.
    Preview · Article · Sep 2011 · Biomaterials
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