**Background:** The International Committee for the Classification of Corneal Dystrophies (IC3D) was established in 2005 to create a modern classification system integrating phenotype, histopathology, and genetic analysis. The first edition (2008) and second edition (2015) addressed the limitations of antiquated nomenclature, which often led to misdiagnosis. This third edition updates the classification based on peer-reviewed publications from 2014 to 2023, incorporating new genetic discoveries and refining the categorization of corneal dystrophies.
**Methods:** The committee evaluated peer-reviewed publications from 2014 to 2023. 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). The classification system retains a category system proposed by Professor Gordon K. Klintworth: Category 1 (gene mapped and identified), Category 2 (mapped to chromosomal locus, gene unknown), Category 3 (well-defined, not mapped), and Category 4 (suspected, not yet convincing).
**Key Results:** Several major updates are presented. Epithelial recurrent erosion dystrophies (EREDs) now include a category 1 dystrophy, epithelial recurrent erosion dystrophy (ERED), caused by COL17A1 mutations on chromosome 10. Franceschetti corneal dystrophy, dystrophia Smolandiensis, and dystrophia Helsinglandica are demoted to category 4, pending confirmation of COL17A1 involvement. Lisch epithelial corneal dystrophy (LECD), previously reported as X-linked, is now classified as autosomal dominant due to MCOLN1 mutations on chromosome 19. Classic lattice corneal dystrophy (LCD) results from the TGFBI R124C mutation. The LCD variant group now includes over 80 dystrophies with non-R124C TGFBI mutations, all demonstrating amyloid deposition. A new nomenclature is proposed for LCD variants, appending the mutation using 1-letter amino acid abbreviations (e.g., LCD-H626R). Pre-Descemet corneal dystrophies now include a category 1 entity, punctiform and polychromatic pre-Descemet corneal dystrophy (PPPCD), caused by PRDX3 mutations on chromosome 10. PPPCD is typically asymptomatic and can be distinguished from category 4 pre-Descemet corneal dystrophy. The update also includes a corneal dystrophy management table. The IC3D classification table lists 22 corneal dystrophies with their categories, including epithelial and subepithelial dystrophies (e.g., EBMD C3, ERED C1, MECD C1, LECD C1, GDLD C1), epithelial-stromal TGFBI dystrophies (e.g., RBCD C1, TBCD C1, classic LCD C1, LCD variants C1, GCD1 C1, GCD2 C1), stromal dystrophies (e.g., MCD C1, SCD C1, CSCD C1, FCD C1, PACD C1, CCDF C4, PDCD C4, PPPCD C1), and endothelial dystrophies (e.g., FECD C1/C2/C3, PPCD C1, CHED C1/C3, XECD C2). Grayson-Wilbrandt corneal dystrophy has been removed.
**Clinical Implications:** The third edition of the IC3D classification provides a current, evidence-based summary of corneal dystrophy information, facilitating accurate diagnosis and management. The recognition of over 80 LCD variants highlights the phenotypic diversity of TGFBI-related dystrophies and the importance of genotyping for precise diagnosis. The new mutation-based nomenclature for LCD variants will aid in consistent reporting and future gene-targeted therapies. The inclusion of PPPCD as a category 1 dystrophy clarifies its genetic basis and distinguishes it from degenerative conditions. The management table offers a broad overview of treatment approaches, from conservative measures (lubricants, bandage contact lenses) to surgical interventions (superficial keratectomy, phototherapeutic keratectomy, deep anterior lamellar keratoplasty, penetrating keratoplasty, endothelial keratoplasty). The article emphasizes that not all corneal dystrophy patients require treatment and that the choice of intervention depends on the patient's symptoms and the specific dystrophy. The IC3D classification is available online at https://corneasociety.org/publications/ic3d, and the Cornea Society has secured the domain www.ic3dcornealdystrophy.org for future updates.