Hereditary cataracts (Australian shepherd type) is an inherited eye disease affecting Australian shepherds. Cataracts are opacities in the lens of the eye caused by structural changes in lens proteins. A normal lens allows light to pass through it to the Retina in the back of the eye. Light cannot pass through the parts of the lens affected by cataracts and vision becomes blurry. Dogs with hereditary cataracts (Australian shepherd type) most commonly present between 2 to 7 years of age with small cataracts that are visible on a veterinary eye exam. Dogs that carry a single copy of the Mutation have an increased risk over the general (normal) population of developing cataracts. In dogs that inherit one copy of the mutation, cataracts develop slowly, sometimes leading to complete blindness. However, it has been speculated that dogs carrying two copies of the mutation are more likely to develop a more rapidly progressing and severe Cataract. Of note, not all forms of cataracts are inherited and environmental factors such as UV damage can also play a role in the severity of disease. This specific mutation in the HSF4 gene shows Incomplete Penetrance, meaning that not all dogs inheriting two copies of the mutation develop clinical disease. This suggests that other unknown genetic or environmental factors may play a role in modifying disease development and progression.