Hi,

I can't really understand what you are asking in relation to the question, could you clarify if I don't address your question?

Changing the focus of the lens of the monochrome video camera will change its focal length. However you still have to move it back and forth to account for the focal length of the IOL which is constant (it's basically like a static glasses lens except right inside the eye). Essentially, you're using the monochrome video camera as a surrogate for the eye to test the suitability of the IOL before you implant it.

As for how the lens of the eye changes its focal length, the ciliary muscles around it will actually bend and change its shape slightly, thereby changing it's focal length. The IOL does not have this available to it as it is a static object that will be implanted in the eye.

I hope this helps!