In various embodiments, a trocar cannula may be configured for insertion into an eye to facilitate insertion and removal of instruments during surgery. The cannula may be affixed to an overcap (to inhibit rotation of the overcap relative to the cannula) that includes a seal. In some embodiments, the seal may be overmolded into the overcap or may include a wafer that is fixed between the cannula and the overcap to inhibit rotation relative to the cannula and the overcap. In some embodiments, the cannula and overcap may snap together through a tab/slot interface in a permanent fashion such that the cannula and overcap may not be separated without damaging the cannula or overcap. In some embodiments, a vent cannula may be receivable in the slit of the seal for allowing fluids to vent from the eye through the cannula (which may include an indentation to frictionally engage the vent).