I always thought Charlie didn't need glasses until well into his old age. Like he's 60's. He would have been in 40's here, right?
I don't know exactly when Charlie began wearing glasses. According to Lita Grey, he was wearing them as early as 1924. He mostly wore them for reading or writing, but there are some photos of him wearing them at events (such as the photo above), so he must have needed them to see far away as well. He wore them more often as he got older.