Surgical tool systems and method

A guided surgical tool assembly comprising:

• an end-effector including a guide tube;
• and
• a surgical instrument having a shaft and a handle, the surgical instrument moveable within the guide tube, the surgical instrument including at least one detectable feature affixed to the shaft or the handle,
• wherein a depth of the surgical instrument in the guide tube is determined by the at least one detectable feature
• wherein the at least one detectable feature comprises a plurality of reflective lens, wherein the plurality of reflective lens from a semi-sphere, and have a radius of curvature terminating at a substantially flat collar or flange,
• wherein the detectable feature comprises at least one reflective lens and the at least one reflective lens is embedded in the handle of the surgical tool.

A guided surgical tool assembly comprising:

• an end-effector including a guide tube;
• and
• a surgical instrument having a shaft and a handle, the surgical instrument moveable within the guide tube, the surgical instrument including at least one detectable feature affixed to the shaft or the handle,
• wherein a depth of the surgical instrument in the guide tube is determined by the at least one detectable feature
• wherein the at least one detectable feature is an optically graduated coating that includes a graduation in light reflectivity extending from a proximal end of the surgical instrument to a darker region adjacent the distal end of the surgical instrument.