Learn Italian: È buio e non ci vedo bene. - It is dark and I can't see well.

In this sentence, ci doesn't mean "us" or "there". It is part of the pronominal verb vederci, which means "to be able to see" (as a physical ability or in a specific condition). While vedere is just "to see" (like seeing a specific object), adding ci changes the focus to your general ability to see in this dark environment. Just like the ci in volerci or metterci, it fundamentally changes the meaning of the base verb.

Why isn't the verb "potere" (can) used here? The English translation says "I can't see well."

In Italian, the verb vederci already implies the physical ability to see. You don't need to add posso (I can) because saying non ci vedo naturally translates to "I can't see" or "I am not able to see".

How is "vederci" conjugated? Does the "ci" change depending on the subject?

The ci stays exactly the same for all subjects because it's a fixed part of this specific verb. You just conjugate the base verb vedere normally: io ci vedo, tu ci vedi, lui/lei ci vede, noi ci vediamo, and so on. This is similar to how the ci remains constant in impersonal verbs like volerci.

Why is it "È buio" and not "Fa buio"? I thought environmental states often use "fare".