Electrical outlets and light switches should be relocated for easy reach. Good lighting is always recommended to make a kitchen safe for everyone, but perhaps even more so for anyone visually impaired, or wheelchair-bound.
With stairs into the kitchen, it may be possible to install a ramp if space allows for a gradual incline. Installing cabinets and work surfaces within a comfortable reach is optimum. If cost is a factor partial replacements and/or modification are possible.
Using turntables inside cabinets to provides easy access to the whole cabinet. If the kitchen is shared with others, a section of counter can be lowered and fit with a small sink and/or cooktop to accomodate to all family members.