an obturator assembly includes a housing configured for operable engagement by a user , a sleeve mounted to the housing and extending therefrom and having a longitudinal lumen , an image passing member positioned adjacent the distal end of the sleeve and adapted to permit an optical image to pass through the image passing member and into the longitudinal lumen of the sleeve , a penetrating member adapted for longitudinal movement relative to the image passing member through a longitudinal stroke of movement to at least partially extend the penetrating member beyond the image passing member and an adjustment member operatively connected to the penetrating member . the adjustment member is movable to selectively vary a longitudinal length of the stroke of movement of the penetrating member , to thereby selectively control extension of the penetrating member relative to the image passing member . the adjustment member may also be movable to selectively vary at least one of a retracted position and an extended position of the penetrating member relative to the image passing member .