Lewis Carroll, author of Alice in Wonderland, suffered from a rare neurological disorder that caused strange hallucinations. The disease was later named after him - Alice in Wonderland Syndrome.

Alice in Wonderland Syndrome was first discovered by English psychiatrist John Todd in 1955, decades after Lewis Carroll's death. However, Carroll suffered from many of the symptoms, particularly hallucinations brought on by migraines. In fact, his books may have been inspired by his experiences with migraines.

It's sometimes referred to as Todd's Syndrome after John Todd. He also sometimes referred to as "Lilliputian hallucinations" referencing another work of fiction, Gulliver's Travels"

This is a type of "macropsia", a condition where objects around you appear bigger than they really are, making you feel really small. This is similar to what happened to Alice in Alice's Adventures in Wonderland" after she drank from the bottle that says "DRINK ME. It also is similar to the city of Lilliput in Gulliver's Travels where everyone is small.
(Sources: 1, 2, 3)