An ocular medical injector is provided for drug delivery. A method includes inserting a puncture member of the medical injector into the eye until the puncture member reaches the suprachoroidal space (SCS). The puncture member defines a lumen therethrough. With the puncture member disposed within the SCS, a flexible cannula is advanced distally through the lumen of the puncture member, beyond the distal end portion of the puncture member and along the SCS towards a posterior region of the eye. The flexible cannula has an atraumatic distal tip and defines a lumen therethrough. With the distal tip of the flexible cannula disposed within the SCS beyond a distal end portion of the puncture member, a therapeutic substance is administered to the SCS.