Posted by: Linda Trunell | November 8, 2013

Friday Fact – Canines Have Third Eyelids

Canines have Third Eyelids

Most animals have nictitating membranes (third eyelids) but humans and pigs do not.  All dogs are born with them.

The third eyelid acts as a “windshield wiper” and clears debris and mucous off the cornea (the clear window in front of the eye).  It also secretes immunological agents to help fight infection and functions to protect the cornea from injury, while contributing a large portion of the tear film that bathes the eye.

What is “Cherry Eye”?

Prolapsed gland of the third eyelid is commonly called “Cherry Eye”.  This happens when the supporting cartilage of the membrane collapses and the third eyelid “pops forward” and it looks like there is a small cherry on the inside corner of the eye.  The third eyelid then loses its “windshield wiper” function.


Photo from Wikipedia – Author Joel Mills

The gland can become very inflamed and look unsightly.  If left untreated it can lose some of its tear function resulting in “dry eye”.

If you notice any change in your dog’s eye, you should call your vet immediately.

Here’s to being our dog’s best friend,



  1. I love your Friday facts, Linda! I learned about this third eyelid a couple of months ago when I had Malika the ER vet after she got hit in the eye with a tennis ball. I didn’t know it at the time that this had happened and to me it looked like her eyeball was in the corner of the socket because the “third eyelid” was swollen and covering the majority of it. I thought she had had a stroke or something!


    • Thank you for visiting! I am always happy to hear that people like the information I’m sharing. That must have been so scary when you thought Malika might have had a stroke. I hope her eye is back to normal.


  2. good to learn about the cherry eye ^ ^



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