Abstract: This disclosure provides new animal models for studying Usher syndrome and developing new therapy. The technology is implemented in pigs, and other large animals in which the ophthalmic architecture and function more closely resembles architecture and function of the human eye. The animals have a genetic modification in which all or a portion of a human gene known to cause Usher syndrome in human patients replaces the host gene. Animals can be cloned or bred to be homozygous at the targeted locus, whereupon they manifest symptoms and signs of Usher syndrome. Since a substantial portion of the targeted gene has been humanized, the animals can be used to develop and test pharmacological agents such as gene therapy that are sequence dependent.