The newest IC3D classification of corneal dystrophies

Abstract

In the year 2015, the International Committee for the Classification of Corneal Dystrophies (IC3D) incorporated new clinical, histopathologic, and genetic information into the former 2008 classification. To this end, the IC3D sighted and evaluated worldwide peer‐reviewed articles for new information on corneal dystrophies published between 2008 and 2014. Using this information, corneal dystrophy templates including categories 1 to 4 and anatomic classification were updated. New clinical, histopathologic, and confocal photographs were added.On the basis of revisiting the cellular origin of corneal dystrophies, a modified anatomic classification was proposed consisting of (1) epithelial and subepithelial dystrophies, (2) epithelial‐stromal TGFBI dystrophies, (3) stromal dystrophies, and (4) endothelial dystrophies. The entity “Epithelial recurrent erosion dystrophies ERED” actually includes a number of potentially distinct epithelial dystrophies (Franceschetti corneal dystrophy, Dystrophia Smolandiensis, and Dystrophia Helsinglandica) but must be differentiated from dystrophies such as TGFBI‐induced dystrophies, which are also often associated with recurrent epithelial erosions. The chromosome locus of Thiel‐Behnke corneal dystrophy is only located on 5q31. The entity previously designated as a variant of Thiel‐Behnke corneal dystrophy on chromosome 10q24 may represent a novel corneal dystrophy. Congenital hereditary endothelial dystrophy (CHED, formerly CHED2) is most likely only an autosomal recessive disorder. The so‐called autosomal dominant inherited CHED (formerly CHED1) is insufficiently distinct to continue to be considered a unique corneal dystrophy. On review of almost all of the published cases, the description appeared most similar to a type of posterior polymorphous corneal dystrophy linked to the same chromosome 20 locus (PPCD1). Anterior segment OCT has emerged as a helpful tool to reveal in vivo features of several corneal dystrophies that previously required histopathologic examination in order to definitively diagnose them.This revision of the IC3D classification includes an updated anatomic classification of corneal dystrophies that more accurately classifies TGFBI dystrophies affecting multiple layers rather than being confined to one corneal layer. At this time, a 3rd edition of the IC3D classification of corneal dystrophies is under way.