In the normal eye, any nontrabecular outflow is termed uveoscleral outflow. Uveoscleral
outflow is also termed pressure-independent outflow. A variety of mechanisms are likely involved, predominantly aqueous passage from the anterior chamber into the ciliary muscle and then into the supraciliary and suprachoroidal spaces. The fluid then exits the eye through the intact sclera or along the nerves and the vessels that penetrate it. As noted, uveoscleral outflow is largely pressure-independent and is believed to be influenced by age. There is evidence that humans, like nonhuman primates, have significant outflow via the uveoscleral pathway. Uveoscleral outflow has been estimated to account for 5%–15% of total aqueous outflow, but recent studies indicate it may be a higher percentage of total outflow, especially in normal eyes of young people. It is increased by cycloplegia, adrenergic agents, prostaglandin analogs, and certain complications of surgery (eg, cyclodialysis) and is decreased by miotics.