There are different kinds of lamp and light switches, so I've had to find gadgets that can modify each switch type.
Foot Switches are good for floor lamps. Arthritis in my shoulders makes it painful to lift my arm high enough to reach the switch. Of course, foot switches will also work well for a desk lamp if the foot switch is placed under the desk.. Locate electric cords where no one will trip over them.
A foot switch is a button that sits on the floor, attached to an extension cord. Some come with lighted foot buttons and I highly recommend that feature. Step on it once to turn the light on, again to turn the light off. Foot switches are sold in hardware stores and small pharmacies. They are also sold for Christmas tree lights and can be bought at a deep discount in After-Christmas sales.
Be careful with electricity, especially if you use it for something other than its intended purpose such as lighting a lamp rather than a Christmas tree. The package of the latest cord I bought says "Rated 125 Volts. Rated 500 Watts for incandescent lamp load only. If watts are not marked on appliances, multiply ampere rating (on nameplate) by 125 to determine equivalent watts. Add determined watts for each plugged-in appliance or lamp (sum of watts on bulbs) to find total watts being used." Since I don't know anything about watts or amperes, I asked to speak to the in-store electrician. He figured out that the specific cord in my hand would work with the lamp (which I had in the store with me). Then when I got home I double-checked with my electrician. Never overload any extension cords or outlets.
Some lamps have a little plastic tube with a fluted cap on it for the switch. These are difficult to grasp because they are so small. My rheumatologist gave me some little extenders to put on these, and they work really well. It is basically a huge triangle-shaped cap that fits on top of the little bitty knob on the lamp. It is very easy to use the weight of my fingers to rotate the switch using this extender.
Slide switches have a knob that slides up and down to dim the light gradually, rather than an on/off switch. The Slide-Switch I have isn't perfect for arthritic fingers because the sliding switch is too small to manipulate easily. Otherwise, it is very convenient to be able to barely switch on the bedroom light in the middle of the night. The light is so dim it doesn't hurt my eyes, but I can see well enough to move around without running into the furniture. It would be easier on my arthritis if the sliding switch was twice as wide.
I have seen some switches that use static electricity. All you have to do is touch a metal panel to turn the light on or off. I didn't buy it and the store had sold out when I went back. I've not been able to find them at any other store, but I would like to try these out. Just touching the switch would clearly be the least painful method to turn on the light, as long as it doesn't give me a shock when I touch it. Let me know if you have tried this type of switch.
I have two problems with a light such as this, either a covered or uncovered bulb in the ceiling with a pull-chain. The first problem is that when the arthritis in my shoulder is acting up, I can't reach up high to turn it on. The second problem is that I can't grasp the little dainty chain with my arthritic fingers. The solution can be found in the accessories section where lighting and/or ceiling fans are sold. The first is to get a pull-chain bob like the dark chain with the crystal show in the photo. This gives me something substantial to grab and pull. Because it is wide, I can just slip the chain between two fingers, close the fingers together and use the weight of my hand to press down on the bob.