Humans are 3D creatures, living in a 3D world, but our eyes can show us only two dimensions. The miracle of our depth perception comes from our brain's ability to put together two 2D images in such a way as to extrapolate depth. This is called stereoscopic vision.
Because your eyes are separated on your face, each retina produces a slightly different image. That difference in images is a direct result of the depth of the objects that we are looking at. When those two images are assembled in your brain, they are interpreted as depth.
In putting, we need our vision to identify our aim point (target), to aim our putter face to it, and to visualize the distance between the ball and the hole.
Unfortunately, our peripheral vision can be a distraction in putting.
The On Point 3D marker allows the golfer to dial-in his/her focus and intensely concentrate, creating the effect of "tunnel vision" which enhances the golfers confidence and ability to make putts.