Dog Hearing and Vision Problems

Selective reproduction has originated some unwilling characteristics, like the Spaniel's hard ears, and the hereditary visual disturbances

Which are the most usual visual disturbances in dogs?
The most important hereditary weakness is the progressive retinal atrophy, a progressive deterioration of the retinal cells in the back part of the eye, affecting image. The first symptoms include a poor night vision. This disease can be expanded through the whole retina, or only the central zone, as in Collies, Labrador and Briard. Among dogs affected by this atrophy many Poodle breeds are included. Unfortunately there's no treatment. However, you can see the characteristic changes, using an ophthalmoscope, to see the retina directly. If you think your dog has difficulties to see, contact your veterinarian. The eye injury can be produced when a dog walks through a thicket, and a sharp branch, or similar object, hits his eyes. If there are any traces of blood, an emergency treatment will be necessary. Sometimes the eye's surface is damaged causing an infection known as keratitis, which is usually painful. An ulcer can be formed in that place if not treated, becoming very hard to cure breeds with prominent eyes, like the Pekinese and the Dogo, are more prone to be affected.

Where is the third eyelid of the dog located?