Kellar is born blind. But he enjoys playing fetch like many doggies.
So this owner helps Kellar learn by using commands like “Listen,Passed it, Hot, Left, Right. This helps Kellar to listen for the dropped ball, Hot for YOU GOT IT ! It looks like the doggie does as good a job as any dog with sight.
I remember reading chapters in a Literature textbook to a classmate who was blind. The teacher gave him the exam with oral questions instead of written ones. With adjustments, we can do the things we enjoy. Just like Kellar.