A 23rd-century medicine used to correct poor vision, to which Kirk is allergic, prompting McCoy to give him antique spectacles in Star Trek II: The Wrath of Khan.
Retinax V is a drug that Starfleet doctors prescribe for deteriorating eyesight, making glasses a thing of the past for most people. It is mentioned in the 1982 film Star Trek II: The Wrath of Khan.
Kirk cannot take it because he is allergic, so for his birthday McCoy presents him with a pair of antique reading glasses several centuries old. The gift fits the film's concern with ageing, and Kirk is seen using the spectacles to read during the battle with Khan.
The glasses return in Star Trek IV: The Voyage Home, where Kirk sells them to an antique dealer in 1986 San Francisco to raise money for the crew.