My optometrist told me I need glasses.

This joke gets its giggle from a classic case of wordplay, specifically a pun. The humor hinges entirely on the double meaning of the word "glasses." When an optometrist tells you that you "need glasses," the immediate and expected interpretation is corrective eyewear to improve your vision. The punchline cleverly subverts this expectation by twisting the meaning to refer to drinking vessels, creating a moment of delightful misunderstanding.

The real-world context that makes this joke work is how common both uses of the word are in everyday life. Many people visit an optometrist at some point to get their eyes checked and potentially prescribed corrective lenses. Equally, "glasses" are a fundamental part of our kitchenware, used daily for beverages. The joke plays on this familiarity, setting up a seemingly serious medical consultation only to pivot to a mundane household item, highlighting the absurdity of the literal interpretation. It's a simple, relatable setup that finds humor in the quirks of our language.