Whether your bird has mobility issues or sight issues, setting up a cage that allows him or her to get around easier is something you should consider. Many of these birds fall easily and often, so a lower height cage is recommended. You will also find that horizontal bars will allow the bird to move and climb more easily. For that reason, a small animal cage may be a better choice over a bird cage. I have found that most bird cages were designed with vertical bars. Vertical bars are much harder for a bird with mobility issues to climb. Although they will learn to adjust with either, the horizontal bars allow most birds to climb with ease.
I have three cockatiels which were given to me with different problems..one is a splay leg, one was born with one leg backwards and the other simply has a split bottom beak. I found that that the cage below not only gives them what they need in order to climb and perch comfortably, it also allows ample room for all of them and it could accommodate a larger bird as well. Midwest makes several sizes and versons of these cages.
The price is comparable to a bird cage; however the lower height ensures the bird's safety while the horizontal bars allow for easy climbing and the shelf allows them to perch comfortably. I also provided my birds with bottlebrush perches which allows them to grasp the perch more comfortably and more naturally. The cage above includes a ladder to the perching/eating shelf which also allows them to climb up more easily.
If you do have a higher cage and a bird that falls alot, you may want to consider removing the grate at the bottom of the cage and add padding under the newspaper. This will allow for a softer landing and result in less injuries.
There are flat perches available throughout the internet. They are offered for sale on different sites; .however, if you are handy, they can easily be made at home. It's important that you use a wood that is bird safe and that has not been treated with chemicals.
With time, patience and a bit of experimenting. You will find a cage set up that works for both you and your bird. Here are a few examples of what different people have done with their cages.