Is this normal?

[TirithMinas]

I've noticed that sometimes I see this strange looking thing in the corner of my rabbit's eye.

In the picture, I'm pulling his eyelids a bit. His eyes usually look normal but sometimes when he moves his eye, I see that weird thing in the corner of his eye. Is this normal for rabbits?

 

[JBun]

Rabbits have a third eyelid. So completely normal.
http://www.medirabbit.com/EN/Eye_diseases/Differential/Nictitating.htm