Though it rarely makes an appearance, the inner eyelid is an important part of the eye structure in both puppies and dogs. Though this inner eyelid is usually light in color, it may also be pigmented. This is never a cause for concern, so long as you distinguish between pigmentation and the redness or swelling which may indicate an actual problem.
The third or inner eyelid is something many pet owners are surprised to discover their dogs possess. Lodged underneath the bottom lid, it is more scientifically known as the nictitating membrane, and all dogs have them. In fact, most other animals have them as well, the exceptions being humans and pigs. Serving as a “windshield wiper” for the eye, the inner eyelid helps keep the eye safe and clean. Your puppy will have this eyelid from birth, and will continue to have it all the way through his life.
Puppies come with a variety of pigmentations, as do dogs of all ages. If you look inside your dog’s mouth, at the pads of his paws, inside his ears or at parts of his skin where there isn’t very much hair, you may notice mottled colors like black, brown, gray and pink. This is totally normal and may extend to the inner eyelid of your puppy. Often times, new puppy owners assume a difference in pigmentation between the two inner eyelids means that something is wrong with one of them. This is rarely true, so look for other signs before deciding there’s a problem.
Usually simple pigmentation is not a problem. Other problems with the third eyelid can occur, however. When the eyelid protrudes into the rest of the eye, especially when the lid is red or irritated-looking, this can pose a major problem. This is called elevation, prolapse or protrustion of the inner eyelid, and many issues can cause this “cherry eye.” If the third eyelid appears for long periods of time, this may indicate the puppy’s eyes are too dry, or more serious problems like corneal ulcer or glaucoma.
There are many reasons animals have the inner eyelid. It keeps the surface of the eye safe and clean by wiping away dirt, debris and possible sources of infection. Underneath the third eyelid covering, there is actually a minute T-shaped structure which functions as an actual wiper to get rid of detritus. The inner eyelid also produces a large amount of the tears that help keep the eye healthy, as well as secreting immune-fighting substances. When the eye is threatened, the inner eyelid closes to keep the cornea from getting harmed.
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