Horopter \Ho*rop"ter\, n. [Gr. ? boundary + ? one who looks.]
(Opt.)
The line or surface in which are situated all the points
which are seen single while the point of sight, or the
adjustment of the eyes, remains unchanged.
[1913 Webster]
The sum of all the points which are seen single, while
the point of sight remains unchanged, is called the
horopter. --J. Le Conte.
[1913 Webster]