Mydriasis disorders e.g. epilepsy, stroke, and impending brain herniation are known to lead to temporal mydriasis as well. A brain catastrophe, or a rapidly increasing brain mass, can cause compression of the oculomotor nerve. In cases of head injury or orbit trauma (eye injury), the iris sphincter (the muscle responsible for closing the pupil) or the nerves controlling it can be damaged, reducing or eliminating the normal pupillary light reflex. A mydriatic is an agent that induces dilation of the pupil. Drugs such as tropicamide are used in medicine to permit examination of the retina and other deep structures of the
Sum of normally distributed random variables more general case we find that the closest point on the line to the origin is located a (signed) distance away, so that The same argument in higher dimensions shows that if then Now we are essentially done, because So in general, if then In the event that the variables "X" and "Y" are jointly normally distributed random variables, then "X" + "Y" is still normally distributed (see Multivariate normal distribution) and the mean is the sum of the means. However, the variances are not additive due to the correlation. Indeed, where ρ is the correlation. In particular, whenever ρ