Why is Depth of Focus Important?

image illustrating depth of focus



The less time spent focusing means faster surgery and less stress caused by muscle and eye fatigue. Which image has the better depth of focus?






Depth of Focus vs Depth of Field:

Depth of Focus (DOF) is the vertical portion of the surgical view that is in focus at any range of magnification. The marginal area of focus on either side of your surgical view is the Depth of Field. They go hand in hand but we will concentrate on the former.

You want to be able to see as much of your patient’s anatomy as possible in focus, especially at high magnification. Here is how you can maximize your depth of focus, increase your resolution as well as reduce constant focusing:

Initially, if you focus on object #1 at low magnification (2x), your object will be out of focus at 12x high magnification. If you start at high magnification and focus on object #2, you will be in focus throughout the range of magnification (#3). As a result, you have Parfocus.

Depth of Field

Parfocality Diagram

Depth Perception:

Depth of Focus and Depth of Field are mechanical. The visual ability to perceive the world in three dimensions and enabling judgement of distance is Depth Perception. The auto iris and/or manual iris plus the stereo base of the optics enhance depth perception. In addition, the wider the stereo base the better depth perception.

Haag-Streit Surgical Microscopes have the widest stereo base of any operating microscope.

Stereo Base

Chuck Luley