Welcome to the forum, that's a fairly old thread that you've found, but obviously relevant to your question
The procedure is different to anything my optician can provide and as the name suggests, they use a digital camera to photograph the back of the eyes. It involves some drops being placed in the eye to ensure that they dilate fully to allow a clear picture of the back of the eye. They always tell you not to drive for a few hours afterwards. I think I'm right in saying that the main purpose is to spot retinopothy which is one of the side effects of high blood glucose. Retinopothy being where the blood vessels narrow, break and leak. High blood pressure can also cause problems.
You say that your husband will control with diet and exercise, I expect that you will have noted that a lot of diabetics choose to lower their carb intake to help control their blood glucose. If he's going to follow the advise that is currently given by UK medics who may talk about the "eatwell plate", you might like to forget that advise and definitely try low carb.
You might also like to ask for a c-peptide test which will indicate exactly how healthy the pancreas is. If it's not performing too well then it's possible that medication will have to be considered later on. A healthy pancreas would suggest that insulin resistance is the problem, which may still require medication later on, but probably easier to handle so long as you get the diet right.
All the best.