[Scanning electron microscopy examination of 87 pre-injection blunted retrobulbar cannulas]

The use of blunt cannulas for retrobulbar injection (retro) is recommended to reduce the risk of retrobulbar hemorrhage and globe perforation. Retro cannulas with blunt tips--so-called Atkinson needles--are commercially available. They can also be produced by being blunted on a sterile surface immediately before injection.

In a prospective study, all retro cannulas (0.5 x 40 mm, Steriseal) used over 8 days in our hospital were collected after being blunted on a sterile Petri dish, followed by injection. Subsequently, scanning electron microscopic examination was performed. 20 unused retro needles were examined for control.

62% (n = 54) of the 87 used retro cannulas were satisfactory, i.e., the tips were blunted, exhibiting no undesirable hooks. 29% (n = 25) of the retro cannulas demonstrated moderate deformation, 9% (n = 8) stronger deformation of the needle tip. No complications occurred after any of the 87 injections.

Blunting of retro cannulas immediately before injection is a possible alternative to commercially available needles with blunt tips. However, this procedure has to be performed carefully to avoid potential detrimental deformation of the needle tip, which can be detected in a low percentage by means of the scanning electron microscope.