Pannus is a lifelong degenerative disease in dogs that can cause blindness if not treated.

It involves the cornea, the clear outer layer of the eye. In the early stages, a thin pink film appears around the corneal edges and spreads toward the center of the eye. As pannus progresses, the film becomes opaque and the cornea darkens. Both eyes are generally involved.

Pannus usually affects dogs 4 to 7 years of age, and German shepherds — purebred or mixed — are at highest risk. It’s more common in dogs living at high altitudes and in areas with poor air quality.

Pannus cannot be cured, but it must be treated to save your dog’s sight. If you notice signs, don’t delay making an appointment with your veterinarian. Pannus is pretty easy to diagnose, but aggressive treatment often involves referral to a veterinary ophthalmologist.