Eye tracking white sclera (limbus tracking). It presents another challenge for vertical eye movements due to obstruction of eyelids. Eye-tracking setups vary greatly: some are head-mounted, some require the head to be stable (for example, with a chin rest), and some function remotely and automatically track the head during motion. Most use a sampling rate of at least 30 Hz. Although 50/60 Hz is more common, today many video-based eye trackers run at 240, 350 or even 1000/1250 Hz, speeds needed in order to capture fixational eye movements or correctly measure saccade dynamics. Eye movements are typically divided into fixations and saccades
The Green Eye of the Yellow God "The Talons of Weng-Chiang", although he misattributes them to music hall comic Harry Champion. Carter the Unstoppable Sex Machine use part of the opening in their song "Perfect Day to Drop the Bomb", which starts "To the north of Kathmandu there's tiny children sniffing glue". The poem is parodied in Series 2 of "Danger Mouse" in the episode "Bad Luck Eye of the Little Yellow God." Tony Randall reads the poem on the episode of "The Muppet Show" on which he guest stars. In an episode of the BBC sitcom "Kiss Me Kate", the character Craig Chapman played by Darren