|Traditional Persian cat with tear staining.|
This nice picture is by Anas Ahmad. The interesting thing is that this is not a flat faced Persian which is known to suffer from tear staining but a doll face Persian cat. The cause is a deformed tear duct which prevents the tears and fluid on the outer part of the eye draining away. It overflows onto the fur below the eye. In this picture it seems that it has flowed down the inside of the nose and then to the outside at the base of the nose. The deformity is due to breeding a overly flat face to conform with the breed standard. This distorts internal anatomy.
As tear duct overflow happens in the traditional Persian as well as the flat faced "ultra" Persian we can conclude that the tear duct is also somewhat defective in the more moderate and normal traditional Persian. This cat still has a rather flat face.