This action, at first sight somewhat obscure, is due to the extreme pupillary contraction which removes the mass of the iris from pressing upon the spaces of Fontana, through which the intraocular fluids normally make a very slow escape from the eye into its efferent lymphatics.
As a result of the extreme pupillary dilatation, the tension of the eyeball is greatly raised.
In a known drug user, sweating, involuntary sniffing and pupillary dilation are helpful physical signs of early withdrawal from opiates.
Recording of pupillary responses consisted of initially setting the threshold value on the computer with the LED turned off prior to each trial.
Other symptoms of total spinal are upper extremity weakness, loss of consciousness and pupillary dilatation.