Introduction

Advances in the genetic analyses of the corneal dystrophies were a key driver in the IC3D ClassiÞcation of Corneal Dystrophies. The genetic dissection of corneal dystrophies identiÞed both genetic heterogeneity, when different genes (cytokeratin 3 and cytokeratin 12) can cause an identical corneal phenotype (Meesmann dystrophy) and phenotypic heterogeneity, when different mutations in a single gene (transforming growth factor, beta-induced or TGFBI) cause different corneal phenotypes (Reis-Bucklers corneal dystrophy, Thiel-Behnke corneal dystrophy, type 1 and 2 granular corneal dystrophy and lattice type 1) [1]. Genetic insights into the pathogenesis and understanding of keratoconus have been more modest. Keratoconus accounts for 25% of the 2,500 corneal transplants performed annually in the UK and a similar proportion of the 32,000 grafts performed in the USA every year [2]. The use of corneal intrastromal ring segments and collagen cross-linking are now established in the clinical management of keratoconus. The ability to develop new therapeutic options and to improve existing treatments depends on understanding the pathogenesis of keratoconus. Despite the visual and social impact of keratoconus, its underlying biochemical and cellular basis is poorly understood. However, there is a body of evidence to support an underlying genetic basis for this disease.

C.E. Willoughby (*) ¥ J. Lechner

School of Medicine, Dentistry and Biomedical Sciences,

Centre for Vision and Vascular Science, QueenÕs University Belfast, Royal Victoria Hospital,

Grosvenor Road, Belfast BT12 6BA, UK

e-mail: c.willoughby@qub.ac.uk; jlechner01@qub.ac.uk