Stargardt disease is a progressive inherited eye disease affecting dogs. Stargardt disease is caused by the degeneration of both Rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. Affected dogs present prior to 10 years of age with signs of vision loss, including dilated pupils and decreased response to light. Affected dogs will have progressive changes in reflectivity and appearance of a structure behind the retina, called the Tapetum, that can be observed on a veterinary eye exam. Additionally, mild to moderate thinning of the retinal blood vessels may also be observed. However, signs of Stargardt disease are subtle in the first two years of life and may not be identified on early eye exams. Stargardt disease severity and speed of disease progression may vary. Dogs may not completely lose their vision during their lifetime, but will develop significant loss of vision, especially in well-lit environments.