Owl Evolution?

Think of the owl.

It has keen eyesight due to it's wonderfully designed eyes that are shaped like a cylinder, unlike normal eyes.

Owls can't move their eyes, they have to rotate their entire head to look at you.

If this owl "evolved", there had to have been a point where the owl's eyes were half-way between normal and cylindrical.

According to Evolutionary theory, this would have potentially spanned thousands of years as the species evolved from normal eyes to cylindrical. 

Unfortunately during this time period, however, the owl would have been blind.

How would it have survived?