A retina transplant is a treatment for blindness, and you can optionally leave out “a treatment”. Note that saying “treatment for blindness” doesn’t actually fix anything, it doesn’t mean you treat someone so that they become blind. You seem to be failing to grasp that someone who says something is “for” a problem generally and commonly means that thing helps solve the problem. It’s an accepted and understood figure of speech, in English and many other languages as well - pretty much all Germanic languages, and it works in French and Spanish. Many words in many languages have vague, abstract, and multiple meanings, that’s a feature of language not a bug. Learn it and embrace it instead of fighting it and you’ll have more fun.
What’s your native language?