This is a test of commonsense. Complete the next sentence:

How to diagnose collie eye in shelties
Test your dog's eyesight.
If you want to know if your sheltie has cea, then test his eyesight. In mild cases, your dog may be able to see well enough to cope.
In severe cases, your dog may be blind. Place objects in your dog's path and see if he avoids them or bumps into the obstruction.