IC3D Classification of Corneal Dystrophies—Edition 3

Abstract

Purpose: The International Committee for the Classification of Corneal Dystrophies (IC3D) was created in 2005 to develop a new classification system integrating current information on phenotype, histopathology, and genetic analysis. This update is the third edition of the IC3D nomenclature. Methods: Peer-reviewed publications from 2014 to 2023 were evaluated. The new information was used to update the anatomic classification and each of the 22 standardized templates including the level of evidence for being a corneal dystrophy [from category 1 (most evidence) to category 4 (least evidence)]. Results: Epithelial recurrent erosion dystrophies now include epithelial recurrent erosion dystrophy, category 1 (COL17A1 mutations, chromosome 10). Signs and symptoms are similar to Franceschetti corneal dystrophy, dystrophia Smolandiensis, and dystrophia Helsinglandica, category 4. Lisch epithelial corneal dystrophy, previously reported as X-linked, has been discovered to be autosomal dominant (MCOLN1 mutations, chromosome 19). Classic lattice corneal dystrophy (LCD) results from TGFBI R124C mutation. The LCD variant group has over 80 dystrophies with non-R124C TGFBI mutations, amyloid deposition, and often similar phenotypes to classic LCD. We propose a new nomenclature for specific LCD pathogenic variants by appending the mutation using 1-letter amino acid abbreviations to LCD. Pre-Descemet corneal dystrophies include category 1, autosomal dominant, punctiform and polychromatic pre-Descemet corneal dystrophy (PPPCD) (PRDX3 mutations, chromosome 10). Typically asymptomatic, it can be distinguished phenotypically from pre-Descemet corneal dystrophy, category 4. We include a corneal dystrophy management table. Conclusions: The IC3D third edition provides a current summary of corneal dystrophy information. The article is available online at https://corneasociety.org/publications/ic3d.

Advancements in Bioengineering for Descemet Membrane Endothelial Keratoplasty (DMEK)

“…Family history is a significant risk factor, suggesting a genetic predisposition to the condition. The relevant genes have been mapped and identified and the specificmutations are known [6]. Hereby are two types of FECD: Early-onset FECD, which manifests in the first decade of life, and late-onset FECD, which occurs after the age of 40 and has a higher incidence compared to the earlyonset form.…”

“…The genetics of the late-onset subtype of FECD appear to be more complex and varied: Typically, there is a mutation in the transcription factor 4 (TCF4) gene on chromosome 18, characterized by an expansion of a CTG triplet repeat. Furthermore, other genes such as transcription factor 8 (TCF8), ATP/GTP binding protein like 1 (AGBL1), lipoxygenase homology domain 1 (LOXHD1), SLC transporter SLC4A11, and transforming growth factor-beta induced (TGFBI) are also implicated [6,7]. Epigenetic factors are also considered in both types of FECD as an additional pathogenetic mechanism [8,9].…”