Abstract: A flexible walled cannula apparatus and method of use comprising a uniquely deformable cannula tube and head in combination with a uniquely shaped obturator which allows the use of heretofore unusable larger gauge surgical instruments while providing a self sealing incision. The apparatus and method of use provides a preassembled obturator and cannula assembly with which the surgeon forms an incision or channel, inserts the cannula tube, and through the cannula inserts surgical instruments to perform a surgical operation. The apparatus and method of use is especially suited for ophthalmic surgical operations. Alternative embodiments for use with even larger diameter instruments utilize a uniquely designed valve having leaflets which prevent bodily or other fluid leakage from the cannula when an instrument is not inserted.