The invention provides a device for treating eyes of a patient. A comfortable insert comprises a retention structure sized for placement under the eyelids and along at least a portion of conjunctival sac of the upper and lower lids of the eye. The retention structure resists deflection when placed in the conjunctival sac of the eye and to guide the insert along the sac when the eye moves. The retention structure can be configured in many ways to provide the resistance to deflection and may comprise a hoop strength so as to urge the retention structure outward and inhibit movement of the retention structure toward the cornea. The insert may move rotationally with deflection along the conjunctival sac, and may comprise a retention structure having a cross sectional dimension sized to fit within folds of the conjunctiva. The insert may comprise a release mechanism and therapeutic agent to release therapeutic amounts of the therapeutic agent for an extended time.