Abstract: A microsurgical injection instrument particularly useful by a physician for injecting a liquid substance or a suspension into a blood vessel in the retina of a subject's eye, includes a handpiece carrying a hollow needle at its distal end, for penetrating the blood vessel. The longitudinal axis of the distal end of the handpiece and of the needle is at an angle of from 120° to 80°, preferably about 145°, to the longitudinal axis of the proximal end of the handpiece to facilitate orienting the needle substantially tangentially to the plane of the subject's retina for penetrating the blood vessel. The instrument may also be used to treat an occluded blood vessel by moving a flexible tube through the hollow needle, after the needle has penetrated the blood vessel, to enter and catheterize the blood vessel.