The mouse Pax6Sey-Neu mutant allele is considered to be a Pax6− null allele and heterozygous Pax6+/Sey-Neu (here abbreviated to Pax6+/−) mice have small eyes, hypoplastic irides and a range of other ocular abnormalities, including corneal deterioration, so provide a good model for human PAX6+/− aniridia and ARK [21]. This evidence concerns the gene PAX6 and aniridia.