Believe it or not, glasses are cybernetics. Yes, that also means a peg leg or glass eye makes the user a cyborg. Cybernetics as a term is much newer than the practice of prosthetics, and cybernetics is simply defined (iirc) as technology for - and the design of the technology for - prosthetic use. Technically “cybernetic” and “prosthetic” are synonyms. The line drawn is implied to be intent: Medical prosthesis to replace what was lost, or cybernetic enhancement?