Retinax V was a medication usually prescribed as a treatment for people with near-sightedness in the 23rd century. Some people, such as James T. Kirk, were allergic to this form of medication, and the alternative of "reading glasses" was therefore still required. (Star Trek II: The Wrath of Khan)
Apocrypha
Since Kirk required glasses to read his book and see Saavik's console up close, it is likely he had become nearsighted with age, not farsighted.