A surgical retractor apparatus having one or more independent, removable extension members adapted to be mounted at the distal end of the retractor, or between the blades of a spreadable retractor, after the retractor has been positioned in the patient, such that a significant portion of the extension member extends beyond the distal end of the retractor to preclude or minimize intrusion of tissue into the access area created by the retractor. The extension members may vary in size and shape so that the most appropriate extension member can be chosen to address the intrusion problem, and the extension members may be mounted at various fixed locations, using clips, mechanical interlocking structures or the like.