Japanese artist Akiyoshi Kitoaka has dedicated his working life to dizzying optical illusions - and the results are pictures so mind-bending they come with a health warning.
Professor Kitoaka, from Ritsumseikan University, in Kyoto, Japan, has spent more than a decade creating his collecting of trippy optical illusion artworks.
His designs have been used by the likes of Lady Gaga, who ran the Kitaoka's work, entitled 'Gangaze,' as the CD cover for her album Art Pop, in 2013.
The professor also devised the now-famous 'Rotating Snake' illusion in 2003, which comes with a warning on his website, due to the feeling of nausea it could cause some viewers.
All of his works stem from Professor Kitaoka's interest in the brain's interpretation of signals from the eyes.
Having originally studied animal psychology, Professor Kitaoka, 52, decided to focus on optical illusions after looking into their effect on monkeys, while working at a neuroscience institute.
Each design is either created through a process of trial and error, or based on illusion experiments of the past, the professor said.
He began designing the images in the mid-90s, and has since created hundreds of different designs.
Optical illusions, which were extremely popular during the Op Art movement of the 1960s, create the feeling that a motionless image is somehow moving.
Professor Kitaoka said: 'I love every work, but Rotating Snakes seems to be the favourite amongst most people.
'I became interested in optical illusions when I worked at a neuroscience institute, twelve years ago.
'Some of my works come from trial and error, whereas others are logical progressions of previous designs.
'My optical illusion works are people's favourites, but the other, more basic illusion images [how something appears one colour, but is actually another, for example] do not get so much attention.'