Variable diameter cannula and methods for controlling insertion depth for medicament delivery

A method, comprising:

• inserting a distal end portion of a puncture member of a medical injector into a sclera of an eye to define a delivery passageway within the eye;
• exerting a force on an actuation rod of the medical injector when a surface of the medical injector is in contact with a conjunctiva of the eye or the sclera of the eye and the distal end portion of the puncture member is in the sclera the force having a magnitude of less than about 6N, the force (1) produces movement of the actuation rod within a medicament container coupled to the medical injector, and (2) increases a length of the puncture member extending distally from the surface of the medical injector to at least one of create or increase a suprachoroidal space or a subretinal space;
• during the exerting the force on the actuation rod, maintaining a force on the medical injector such that the surface of the medical injector forms a substantially fluid-tight seal with the conjunctiva of the eye or the sclera of the eye;
• and
• conveying, in response to the exerting, a substance from the medicament container into the suprachoroidal space or the subretinal space via the puncture member when the distal end portion of the puncture member is disposed within the suprachoroidal space or the subretinal space.

A method, comprising:

• with a distal end portion of a puncture member of a medical injector extending distally by a first distance from a distal end surface of the medical injector, inserting the distal end portion of the puncture member into a first region of an eye to define a delivery passageway within the eye;
• with the distal end portion of the puncture member disposed in the first region, exerting a force on an actuation rod of the medical injector, the force produces movement of the actuation rod within a medicament container coupled to the medical injector and causes the distal end portion of the puncture member to move relative to the medical injector such that (1) the puncture member extends distally by a second distance from the distal end surface of the medical injector and (2) the distal end portion of the puncture member is moved into a second region of the eye, the second distance being greater than the first distance;
• and
• conveying, in response to the exerting, a substance from the medicament container into the second region via the puncture member when the distal end portion of the puncture member is disposed within the second region such that the medicament flows from the second region to a posterior segment of the eye, both the first region and the second region being in an anterior segment of the eye.