Beginning surgeons do not always realize that the force created by using small 27g cannulas can be quite high. If the cannula inadvertently comes loose, it can forcefully shoot off the tip of the syringe and into the eye, causing significant iatrogenic trauma and damage. The surgeon must not rely solely on the Luer lock to hold the cannula in place. In addition, the fingertips should directly hold the hub of the cannula so that it cannot accidentally release.
click below to watch this video and learn how to use a cannula safely: