Reading on dim light can worsen your vision?

No, it does not. I have studied eyesight and how the eyes work. A dim light will not harm the eye and the retina will not have to work harder. It all depends on an individual's preference and comfort zone. If they are able to read in a dim light, let them do that. If it is difficult for someone, turn on a light. Simple as that.

Yes. Reading on a dim light will deteriorate your eyesight. If the place you're reading at is not well-lighted, you're eyes will have to exert extra effort for you to be able to read the texts. I have damaged my eyes young because we had no electricity until I was in secondary school. I have studied using a gas lamp. It's light is not as bright as that of an electric light bulb.

I do not like reading with dim light--now, anyway. Reading with dim light can strain the eyes which causes headaches, blurred vision, sore eyeballs, back and neck aches and drooping eyelids. Eye strain can also cause nearsightedness. When I was younger, I used to read in the dark, sometimes using flashlight. My mother would scold me about my addiction on reading pocketbooks because I was neglecting my lessons. So, I would secretly read in my room when I was supposed to be asleep. I used to have migraine attacks then that would keep me in bed the whole day. Right now, my eye grade is -325.

Yes it does, and it does really bad things to your eyes as the retina needs to work harder in order to adjust the eyesight to the proper light, your eyes will be burdened by this. Trust me, go for as much light as you can get meaning the light that does not hurt your eyes but is enough to properly read.