This breed is also commonly screened for congenital stationary night blindness (SNB) with a DNA test. SNB is inherited through recessive genes.  Progressive retinal atrophy PRA, is a disease that causes nerve cells at the back of the eye to degenerate. The condition usually begins in older pets and can lead to blindness.  Progressive retinal degeneration or atrophy (PRD/PRA) represents a group of inherited eye diseases characterized by abnormal development or premature degeneration of the retina. There are two types of photoreceptors in the retina and these are the light-sensitive rods and cones. They are responsible for detecting light and converting it into an electrical signal that travels to the brain. When the photoreceptor cells deteriorate, vision is lost because the animal has no way to generate an image from the light reaching the retina. Puppies are usually blind before one year of age.  For the first time ever, animals (Briards) that were born blind gained the ability to see after undergoing gene therapy, according to research from the University of Florida, Cornell University and the University of Pennsylvania. UF researchers had established that the apparently harmless adeno-associated virus can carry healthy copies of a gene into the cells of the retina, which is composed of layers of light-sensitive nerve cells. The healthy gene's mission: to produce a protein critical to translating light waves into nerve impulses that can be interpreted as images by the brain. The study was successful and the puppies could see in the eye that was treated. Officials from the Foundation Fighting Blindness, which supported the study with grant funds, said the success in reversing blindness in dogs is an important advance.