The canine eye is truly amazing. Watch this video of about what a Chow and Shih Tzu sees in their world. View a dog's view of the world to better understand their behavior.
Also there are videos of the various types of eye problems as a reference to dog parents. Be aware, that constant exposure of your Chow or Shih Tzu puppy to bright light can lead to many eye issues. A dog should always have free access to a dark place.