Karl, a 28-year-old man living in the northeastern United States, experiences a rare visual phenomenon in which features of his grey tabby cat, Luna, appear superimposed on the faces of people he encounters. This condition, documented in a report published in the journal Cortex, involves a form of palinopsia that leads to face distortions known as prosopometamorphopsia, or PMO.
Karl’s symptoms began two years ago following a surgical procedure in which part of his right temporal lobe was removed. The surgery was necessary to treat an arteriovenous malformation, a tangled mass of blood vessels between arteries and veins that can lead to a brain bleed if left untreated.
In the mornings, Karl’s cat is often the first face he sees. On some days, this initial exposure to Luna’s face triggers a persistent visual effect where he sees the cat’s almond-shaped eye sockets, enlarged pupils, and stripes on the human faces he encounters later in the day. This transfer of features occurs whether he is interacting with people in person or viewing them online. Conversely, if Karl sees a human face at the start of his day instead of his cat, he may perceive that person’s pupils and eye shape on oth...