A cataract describes any opacity of the normally transparent & avascular lens. A “hypermature” (or “Morgagnian”) cataract describes a cataract in which the lens cortex has begun to liquefy & resorb. The lens nucleus may sink & the capsule shrink, fibrose & calcify. Hypermature cataracts typically have a crystalline appearance & are frequently associated with symptoms of chronic uveitis. Variable degrees of tapetal reflectivity and/or visual impairment may be present. Many breeds (& mixed breeds) may be affected by hereditary cataracts and many breed-related features including age of onset and rate of progression are described. Commonly affected breeds include the Boston Terrier, Bichon Frise, Cocker Spaniel, Labrador Retriever, miniature Schnauzer, miniature Poodle & Siberian Husky.