Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

182 •DOG OWNER’S HOME VETERINARY HANDBOOK
These growths on the eyelids are meibomian gland adenomas.
EYELID TUMORS
The most common tumor of the eyelid is a meibomian gland adenoma.
Meibomian glands are found only on the eyelids. These glands secrete an oil
that acts as a barrier to prevent the evaporation of tears. Meibomian gland
adenomas have a cauliflowerlike appearance and may be single or multiple.
Among other eyelid tumors, the most common is the sebaceous adenoma.
Most are benign, and are found in older dogs.
Papillomas are wartlike tumors caused by the canine oral papilloma virus.
These tumors also grow on the surface of the eye.
Treatment: Eyelid tumors should be removed to prevent injury to the
cornea. The tumors mentioned here are not usually malignant tumors.
The Nictitating Membrane (Third Eyelid)
FILM OVER THE EYE
An opaque third eyelid, normally not seen, may become visible across the
front of the eye, in which case the nictitating membrane is protruding. The
appearance of the third eyelid indicates that the eyeball has sunken into its
socket (see Enophthalmos, page 176), or that the eyeball has been pulled back
into its socket by spasm of the retractor muscles in response to severe eye pain.
A dog may be born with visible third eyelids, called haws. In the show ring
this is often considered undesirable, because it gives the animal a somewhat