Unity 5.1.2f1, Yosemite
Just using the scroll wheel causes this ![]()

Unity 5.1.2f1, Yosemite
Just using the scroll wheel causes this ![]()

Have a look at your Main Camera’s Near Clipping Plane value. You may need to make this value smaller.
You shouldn’t really do this unless you have some specific need to do so though
Refer to the clip plane section of the camera manual:
edit: actually, you were referring to the Scene camera. The main camera’s near clipping plane is only for the game camera.
Perhaps refer to this Unity Answers question
Crap, didn’t know that!
It’s a weird behavior for an editing view though, I thought it was a bug.
Thanks!