[George Pope]

George Pope  asked the Naked Scientists:
   
When a person or animal falls asleep, they tend to wake with something normally called sand in the corner of their eye sockets. It has been referenced to in movies such as Santa Clause 3.

My question is: What biological process causes the material to gather?

What do you think?

[gora]

I would think that there is nothing great involved here, just that you are not moving them and they lying on one side or other through out probably causes the tear fluid in the eye to collect at the edge due to gravity and with which will be some dissolved salts which would have crystallized due to exposure to air.