third eyelid

The surgery was complicated by the unique characteristics of penguins, such as a third eyelid, which protects their eyes underwater but had a tendency to close during the surgery.

His daughter searched for information online and learned about a membrane, or third eyelid, that protects the birds’ peepers in-flight and on fishing expeditions.

But the third eyelid actually plays an important role in maintaining the eye's health.

A third eyelid, between the regular eyelids and the cornea, protects the globe and also has a gland at the bottom that produces extra tears.

The eye is provided with a nictitating membrane or third eyelid, at the base of which open the ducts of the Harderian gland.