The Portuguese Water Dog is a breed of dog. It is classified as a working dog by the American Kennel Club. The Portuguese Water Dog is a breed of dog. It is classified as a working dog by the American Kennel Club. Cataracts and progressive retinal atrophy are two eye diseases found in PWDs. Progressive retinal atrophy, which causes 'night blindness', may lead to complete blindness. This is a simple recessive gene. At this time, there is no known cure or treatment but there is a way to prevent producing puppies affected by juvenile dilated cardiomyopathy.