The IC3D Classification of Corneal Dystrophies

Department of Ophthalmology, Kresge Eye Institute, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Cornea (Impact Factor: 2.04). 01/2009; 27 Suppl 2(Suppl 2):S1-83. DOI: 10.1097/ICO.0b013e31817780fb
Source: PubMed


The recent availability of genetic analyses has demonstrated the shortcomings of the current phenotypic method of corneal dystrophy classification. Abnormalities in different genes can cause a single phenotype, whereas different defects in a single gene can cause different phenotypes. Some disorders termed corneal dystrophies do not appear to have a genetic basis.
The purpose of this study was to develop a new classification system for corneal dystrophies, integrating up-to-date information on phenotypic description, pathologic examination, and genetic analysis.
The International Committee for Classification of Corneal Dystrophies (IC3D) was created to devise a current and accurate nomenclature.
This anatomic classification continues to organize dystrophies according to the level chiefly affected. Each dystrophy has a template summarizing genetic, clinical, and pathologic information. A category number from 1 through 4 is assigned, reflecting the level of evidence supporting the existence of a given dystrophy. The most defined dystrophies belong to category 1 (a well-defined corneal dystrophy in which a gene has been mapped and identified and specific mutations are known) and the least defined belong to category 4 (a suspected dystrophy where the clinical and genetic evidence is not yet convincing). The nomenclature may be updated over time as new information regarding the dystrophies becomes available.
The IC3D Classification of Corneal Dystrophies is a new classification system that incorporates many aspects of the traditional definitions of corneal dystrophies with new genetic, clinical, and pathologic information. Standardized templates provide key information that includes a level of evidence for there being a corneal dystrophy. The system is user-friendly and upgradeable and can be retrieved on the website

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    • "In this study, we describe histopathological findings and a novel mutation in the CHST6 gene (p.Arg205Trp [c.613C>T]) in a case of MCD [7]. Light microscopy revealed abnormal deposits of glycosaminoglycans in Bowman's histiocytes and keratocytes, as well as between the stromal lamellae, Descemet's membrane, and endothelium. "
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    ABSTRACT: To report a novel mutation within the CHST6 gene, as well as describe light and electron microscopic features of a case of macular corneal dystrophy. A 59-year old woman with macular corneal dystrophy in both eyes who had decreased visual acuity underwent penetrating keratoplasty. Further studies including light and electron microscopy, as well as DNA analysis were performed. Light microscopy of the cornea revealed glycosaminoglycan deposits in the keratocytes and endothelial cells, as well as extracellularly within the stroma. All samples stained positively with alcian blue, colloidal iron, and periodic acid-Schiff. Electron microscopy showed keratocytes distended by membrane-bound intracytoplasmic vacuoles containing electron-dense fibrillogranular material. These vacuoles were present in the endothelial cells and between stromal lamellae. Some of the vacuoles contained dense osmophilic whorls. A novel homozygous mutation (c.613 C>T [p.Arg205Trp]) was identified within the whole coding region of CHST6. A novel CHST6 mutation was detected in a Korean macular corneal dystrophy patient.
    Full-text · Article · Dec 2013 · Korean Journal of Ophthalmology
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    • "The combined features of lattice and granular dystrophies in the same cornea resulting from mutations in the same gene raises the questions of validity of relying solely on clinical and histological evidence to classify disease. Modern genotyping now enables greater accuracy in the nosology and the International Committee for Classification of Corneal Dystrophies (IC3D) has already incorporated this information into their recent reclassification of these dystrophies [3]. Initial clinical symptoms of the heterozygous form of ACD appear during the first or second decade of life. "
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    ABSTRACT: BACKGROUND: Avellino corneal dystrophy (ACD) is an autosomal dominant disorder, characterized by the presence of deposits in the anterior stroma, and results from a specific mutation (R124H) in the transforming growth factor beta-induced gene (TGFBI). This report presents corneal dystrophy of the Bowman layer as a rare phenotypic appearance of ACD and a high intra-familial variability of phenotype in patients with ACD. CASE PRESENTATION: A 56 year-old Caucasian woman with recurrent corneal erosions was diagnosed with corneal dystrophy of the Bowman layer after a clinical examination. Optical coherence tomography of the anterior segment (AS-OCT) mainly demonstrated deposits in the Bowman layer and a few deposits in the superficial stroma. Her son, a 36 year-old man, has a typical clinical presentation of ACD with all the deposits arranged in stromal layers. In his case, the opacities resemble snowflakes between the granular deposits, and AS-OCT shows large, snowflake-like deposits in the superficial and deep stroma without accumulation in the Bowman layer. Genetic screening in both cases shows the heterozygous R124H mutation in the TGFBI gene. CONCLUSION: The clinical finding of the granular-lattice corneal dystrophy in which deposits are located in the Bowman layer may be an atypical presentation of ACD. This paper demonstrates a high degree of variability in the quantity and form of deposits between ACD heterozygotes. This is the first description of Avellino corneal dystrophy in the Balkans and in Serbia.
    Full-text · Article · Jul 2013 · BMC Ophthalmology
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    • "The diagnosis of FECD was based on clinical signs on the slit lamp examination (occurrence of endothelial guttae, corneal edema) and in all the cases was confirmed by the presence of characteristic lesions and polymegathism and pleomorphism of the endothelial cells on in vivo confocal microscopy (IVCM) examination [19, 20]. The control subjects had no clinical evidence of FECD and presented healthy corneal endothelium on IVCM. "
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    ABSTRACT: Fuchs endothelial corneal dystrophy (FECD) is a slowly progressive eye disease leading to blindness, mostly affecting people above 40 years old. The only known method of curing FECD is corneal transplantation. The disease is characterized by the presence of extracellular deposits called "cornea guttata", apoptosis of corneal endothelial cells, dysfunction of Descement's membrane and corneal edema. Oxidative stress is suggested to play a role in FECD pathogenesis. Reactive oxygen species produced during the stress may damage biomolecules, including DNA. In the present study we evaluated the extent of endogenous DNA damage, including oxidatively modified DNA bases, and damage induced by hydrogen peroxide as well as the kinetics of DNA repair in peripheral blood mononuclear cells of 50 patients with FECD and 43 age-matched controls without visual disturbances. To quantify DNA damage and repair we used the alkaline comet assay technique with the enzymes recognizing oxidative DNA damage, hOGG1 and EndoIII. We did not observe differences in the extent of endogenous and hydrogen peroxide-induced DNA damage between FECD patients and controls. However, we found a lower efficacy of DNA repair in FECD patients as compared with control individuals. The results obtained suggest that the lowering of the DNA repair capacity may be one of the mechanisms underlying the role of oxidative stress in the FECD pathology.
    Full-text · Article · Dec 2012 · Molecular Biology Reports
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