What I would do is see if you can ride on the back of a bike to test the experience first.

Have someone else ride and get a helmet that has a clear, not tinted visor.

A lot of helmets have tinted visors which are dark to block out the sun but a long with that you block out some details of the road.

So get a helmet that has a clear visor on it and get a full face helmet so no wind, bugs or debris goes into your eyes.

I am aware of what retinitis pigmentosa and it is the narrowing of the field of vision.

I can imagine that riding on freeways without any blind corners or dangerous corners would be no problem at all but going up into the mountains and riding the twistys might present itself with a problem.

Also what I have found helps alot before I go riding, and I have no vision problems but still I do it..is I ROUTE the ride on a map.

Some roads are horrible with crumbles in the road and then dangerous twists and turns so I prefer a straighter path to my destination.

I get out a map and route the way I am going before I go. The less curves the better. For example my ride to work used to be dreadful. It went by roads where the road was all messed up and its hard on the tires ya know..so I looked on the map and got another route.

That route was better but still some roads were harsh. After re routing it 3 times I now have a great route to work and no stress.

I would say your vision would actually be less restricted on a bike as there is nothing like car frames etc. blocking your vision and you can turn your head around and scan.