The breed standard recognizes four colors: Blenheim (chestnut and white), Tricolor (black/white/tan), Black and Tan, and Ruby. The usual cause of this condition is an autoimmune reaction against the dog's lacrimal gland (tear gland), reducing the production of tears. According to the Canine Inherited Disorders Database, the condition requires continual treatment and if untreated may result in partial or total blindness. 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.