This vectogram are an example of what I stare at for 30 minutes in vision therapy sessions to see if I can see both images at the same time. I wear glasses with one red plastic lens and one red lens. Sometimes I also use a prism over one of the eyes. Vectograms are translucent sheets of a matching image. I am supposed to see one sheet with one eye and the second sheet with the other. My brain is supposed to fuse the images into one single 3 dimensional image. The doctor moves the sheets around so that the distance separating the sheets changes the difficulty of the task. The exercise helps to develop strong use of both eyes (binocularity).