This Wild Ohio Video posted October 7, 2013.
This Screech Owl gives us a close up view of the Nictitating Membranes and how they are used to protect the eyes.
The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Screech owls close this membrane when they are catching prey. They can see through it just fine and it enables them to protect their eyes from injury.
Great Horned Owl Nictitating Membrane
Crocodile Nictitating Membrane in slow motion