Can someone tell me how long will a persons eyes stay dilated after using cocaine?

Depends. Cocaine is metabolized rapidly. In people who are habituated to it, the dilated pupils can be followed by constricted pupils. How long also dependent on how it is taken - smoked (crack) is fastest), inhaled a bit slower. Overall, two hours is a rough measure of how long it takes for half the drug to be gone. But urine tests are positive up to 3 days after Cocaine eye drops are used for surgery.