The Cavalier King Charles Spaniel is a small spaniel classed as a toy dog by The Kennel Club and the American Kennel Club, that originated in the United Kingdom. Since 2000, it has grown in popularity in the United States and ranks as the 19th most popular pure-breed in the United States. The breed standard recognizes four colors: Blenheim (chestnut and white), Tricolor (black/white/tan), Black and Tan, and Ruby. The breed is generally friendly, affectionate and good with both children and other animals; however, they require much human interaction. As such, dogs of the breed are good with children and other dogs. Cavaliers are not shy about socializing with much larger dogs. This disorder can decrease or heal over time.A 1999 study of Cavaliers conducted by the Canine Eye Registration Foundation showed that an average of 30% of all Cavalier King Charles Spaniels evaluated had eye problems. They include hereditary cataracts, corneal dystrophy, distichiasis, entropion, microphthalmia, progressive retinal atrophy, and retinal dysplasia.