It was found by the use of models approximating the in vivo state that there is a two-step response of a simulated precorneal tear film to blinking. The first is from the upper lid pulling the tears over the cornea by capillary action. The second is due to the relatively slow spreading superficial oily layer which drags along a second layer of "tears" to thicken and stabilize the "precorneal tear film." A two-step phase after blinking was seen at the slit lamp biomicroscope in vivo, and a correlation with the tear film model was suggested. Spotwise drying of the precorneal tear film was also explained.
Brown SI, Dervichian DG. Hydrodynamics of BlinkingIn Vitro Study of the Interaction of the Superficial Oily Layer and the Tears. Arch Ophthalmol. 1969;82(4):541-547. doi:10.1001/archopht.1969.00990020543020