Dear Daisy Dog
When my dog Murphy dozes, an opaque white membrane crosses each eye. Sometimes his eyelids are closed; other times, they’re open. Should I have the veterinarian check this out?
As long as his eyes appear normal when he’s awake, I think you have nothing to worry about.
The white membrane you’ve seen is Murphy’s third eyelid, called the nictitans or nictitating membrane. The third eyelid provides an extra layer of protection for dogs’ and cats’ eyes.
When we’re awake, the third eyelid retracts into the bottom inner corner of the eye. When we sleep, it moves up underneath the outer eyelids to cover the eye. And sometimes when we doze, it covers the eye even when the outer lids remain open.
If you ever see the third eyelid partially or completely cover Murphy’s eye when he’s awake, it may mean that his eye is injured and it hurts. If that happens, take Murphy to the veterinarian as soon as possible.
The other time you might see a dog’s third eyelid is if the gland attached to it becomes inflamed. The condition is called cherry eye, because the swollen, red gland looks like a small cherry.
While it sounds like Murphy’s third eyelid is operating normally, please don’t hesitate to contact your veterinarian if you have any concerns about his eyes. Vision is important to us dogs, and some eye problems, if not treated promptly, can lead to blindness.