The reason why the eyes of Persian and Himalayan cats water will often be because the cats are bred to extreme. Himalayans are Persian cats with a pointed coat.
The contemporary Persian is bred to have a round head and flat face. This is a brachycephalic head. Their eyes are large, round and prominent. You’ll see badly bred Persians with oversized, bulging eyes and undershot paws. Frankly a sad mess and very unfortunate for the cat.
The flat face causes a narrowing of the duct at the corner of the eye near the nose which carries away tears (the nasolacrimal duct). This causes tear duct overflow which in turn leads to the staining you see in a dark channel below the eye next to the nose.
These breeding factors combine to create a cat with ‘chronic eye irritations and infections that produce tearing’ 1.
An overflow of tears from the eyes is called ‘epiphora‘. The excess tears compound the problem as they can cause dampness beneath the eyes. This can lead to skin irritation and infection.
Although these eye problems are associated with Persian and Himalayan cats because of extreme breeding, a vet will have to do some box ticking to make sure that the cat is not suffering from illnesses such as an allergy, abnormal eyelashes, conjunctivitis, clogged tear duct, corneal ulcer or an eye infection to name some.
As the question in the title links Persian cats and watering eyes, the answer is essentially to do with extreme breeding by breeders who follow the cat association’s breed standard (guide as to physical appearance) which has evolved over 60 or more years to obligate breeders to create unhealthy cats. They do this because they believe that the cat looks more interesting.
In the middle of the 20th century Persian cats did not have these faces. They were standard looking cats. These are now called ‘doll face Persians’ while in India they call modern Persians ‘punch face Persians’ which is a reflection on the flat (as if punched) face. There is a price to pay for this ‘interesting’ but odd appearance.
1. Page 186 of Cat Owner’s Home Veterinary Handbook 3rd edition.
2. VCA Hospitals