My doctor said I need glasses.

This joke tickles our funny bone through a clever mix of misdirection (Review) and a delightful reversal of expectations. The initial setup leads us to believe the doctor is giving a medical diagnosis to the patient, which is a very common and relatable scenario. We anticipate the patient will react to needing glasses, perhaps with surprise or resignation.

However, the punchline brilliantly flips the script. Instead of the doctor diagnosing the patient, it's revealed that the doctor themselves might be the one in need of an eye exam, or perhaps has made such a blunder that they're humorously admitting to needing help. This absurdity, where the medical professional tasked with assessing vision turns out to be visually impaired themselves, creates a laugh by subverting our understanding of the doctor's role and their supposed expertise. It's a classic example of finding humor in a slightly silly, self-deprecating twist.