I too am disabled, but I'm bed-bound 24/7.
I have obviously had to adapt and one of the first things that had to got was my DSLR as it was to heavy for me.
I traded down for a canon G11 and with the sale of my telescopes and astrophotography gear have now grabbed a Panasonic G1 and a few lenses.
I have gone down the macro route to a degree, friends and family, even my carers all bring me in interesting objects or plants they find laying around, for me to shoot.
I also have an area with a blank wall I can use for portraits and an open window I can shoot through for moon, bird etc shots.
It's not so much about our disability as it is our ingenuity in either overcoming or side-stepping the problems they bring us.
I for instance am stuck in a specialist metal framed profiling bed, but found a wheeled table cheap in argos that I could use for a little studio, I then got a little 1ft light cube and a couple of bright led lights and voilà!! macro studio !!
I also got an little manfrotto modo tripod thats small enough for me to manage and will carry either camera I use with no issue, the really great thing is its so versatile and flattens out almost completely, I am also getting an opticron hide clamp, centre column and 3 way head which will clamp to the side of my bed giving me a stable platform for larger lenses (something thats been an issue in the last 24 hours) for shooting birds and the moon etc.
My next plans are to get some turf in a cat litter tray, sow it with wildflower seeds and create a mini meadow on the table next to the bed so I can shoot it and the creatures I hope will find their way into it.
So don't give up.. just adapt to what you can manage on the day and make the most of it.
PS I think the opticron hide clamp might adapt to mounting on a wheelchair if you need one.