Device for injecting a substance into an interlayer of a body tissue or organ

A method for performing suprachoroidal buckling in an eye of a subject, the method comprising:

• providing a device for injection into an interlayer of an organ of the subject, the device comprising:
• a needle comprising a needle lumen extending between a needle proximal end and a needle distal end, said needle distal end terminating in a sharp needle distal tip;
• an elongated tissue separator having a separator distal tip, at least a portion of said elongated tissue separator being shiftable in said needle lumen;
• and an actuator configured to shift said elongated tissue separator in said needle lumen between a first position, wherein said separator distal tip is positioned proximally to said needle distal tip, and a second position, wherein said separator distal tip is positioned a first predetermined distance distally from said needle distal tip;
• using said sharp needle distal tip to partially penetrate at a penetration point into a sclera of the eye, not completely through the sclera;
• moving said elongated tissue separator distally within said needle lumen such that said separator distal tip moves distally to said sharp needle distal tip and penetrates into a choroid of the eye and forms a suprachoroidal passage in the choroid;
• and
• using the device to inject a fluid into the suprachoroidal passage, the fluid comprising a therapeutic composition comprising viscous agents to achieve suprachoroidal buckling, comprising a short term buckling effect or a long term buckling effect.