You could try the RNIB for further information about the condition and increase your knowledge about it and what could help him.
Remembering it's his condition is important so make suggestions for him to take in and decide what he wants to do and try.
There is a website for an organisation...
http://www.maculardisease.org/
There may be local groups or contacts who could help. show he's not alone and support is out there.
There is also a US support one.
http://www.maculardegeneration.org/
One idea may be to ask him how you can help and support him. He may need to go away and think about it but he knows you're thinking of him and may well come back with some great ideas.
If he's not very approachable in that way, maybe put it (with some info) in a card for him somewhere he'll find it and can look at privately.
Some more general info here...
http://www.rnib.org.uk/xpedio/groups/public/do cuments/PublicWebsite/public_whatsnext.hcsp