Mydriasis surgery. Mydriasis Mydriasis () is the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, trauma, or the use of drugs. Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. A "mydriatic" pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a
Sum of normally distributed random variables variables is normal, with its mean being the sum of the two means, and its variance being the sum of the two variances (i.e., the square of the standard deviation is the sum of the squares of the standard deviations). If one is to get the conclusion that the sum is normally distributed, the assumption that "X" and "Y" are independent cannot be dropped, although it can be weakened to the assumption that "X" and "Y" are jointly, rather than separately, normally distributed. (See here for an example.) The result about the mean holds in all cases, while the result