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
Tache noir de la sclerotique eye, which becomes brown and then black within a few hours, upon which dust settles and the surface becomes wrinkled. Tache noir de la sclerotique Tache noire de la sclerotique (French for "Black spot of the sclera") is one of the ocular signs of death in which a reddish-brown discoloration is transversely arranged across the sclera. It occurs when the eyes are not completely closed so that the sclera is exposed to air. If the eyelids are open for a few hours after death, a film of cell debris and mucus forms two yellow triangles on the sclera, each at