It can be a sign of fear and stress in sheltered dogs. Some shelters will let you take them out for a walk just outside. If you can take him outside for a little walk, see if he relaxes so you can notice any change in them in the natural daylight.
Ask if he's had a good physical exam and call it to their attention. If you tell them your interested in adopting the dog but don't want to take a dog with eye problems or with another physical problem this could be a symptom from, maybe they will do a more intensive medical work up on him to try to get him a good home.
Hopefully it's just coming from his stressful environment, I've adopted shelter dogs and know that they become nervous and scared from all the noises and different dogs around them. A puppy might be even more afraid if he's just been separated from his mother and coping with that also..
I hope he's fine and can get a good home, and it's great your friend is adopting instead of buying a dog.. good for her.
The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. MedHelp is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.