This is a pretty specific clinical question on signs and documentation that no one here can and shouldn't be answering. Your job as a biller is to bill what the physicians gives you and his job is to code or have a Certified Coder code from the medical record itself. As a biller you should be looking for obvious problems or mistakes that don't require the actual medical / clinical record. If your provider is giving you this to do coding and you are not an experienced and/or certified coder it's best to hand it back to him to look over.
Your question was this:
"What clinical signs do you need to bill for hypertensive retinopathy"
Your provider should know what "clinical signs" should be documented. If it's not documented, it's not done, not done, no code.