High Quality Content by WIKIPEDIA articles! In studies of binocular vision the horopter is the locus of points in space that yield single vision. This can be defined theoretically as the points in space which are imaged on corresponding points in the two retinas, that is, on anatomically identical points. An alternative definition is that it is the locus of points in space which make the same angles at the two eyes with the fixation lines. More usually it is defined empirically using some criterion.