Best answer:

Answer by Peter H
1. The diabetes. The management on the cruise will be the same as on land. The diabetes should be stabilised, the stock of insulin etc sufficient. The diet on the ship may well be different, but the ship’s doctor and crew should have the information. Being seasick and unable to take anything in could be a problem.
2. The retinopathy. The short answer is “Don’t fall off the gang-plank”, but clearly difficulties with vision may be a real problem in a strange environment, particularly if that environment is going up and down and sideways.
3. Travel insurance. You need the insurance and the diabetes must be declared. The ship’s doctor needs to know as well.

Diabetes affects a lot of systems. I assume the blood pressure is under control, that leg ulcers are under control, and the kidneys are still in order. Enjoy the cruise.

Add your own answer in the comments!