Had they gone blind, then yes. What will be hard to deal with, is if Dipper loses what little sight he has.

Don't know about that. My second seeing eye dog lost his eyesight at six years old. He had about a two week adjustment. And then he just went on being his happy, energetic dog self. Everyone is an individual and we all differ how we handle things. I've known people who were born blind who absolutely wouldn't accept it, and people who lost their eyesight later in life who never broke stride and just kept living. One man I know was 58 years old when his eyesight Suddenly failed, but he didn't let it stop him. Just a small adjustment period and he was up and running again.