Definition of horopter in US English:



  • A line or surface containing all those points in space whose images fall on corresponding points of the retinas of the two eyes.

    • ‘All the points common to both the horizontal and vertical line horopters have the same direction in each eye.’
    • ‘The experimentally determined horopter deviates from the Vieth-Muller circle and is closer to the objective frontal plane passing through the fixation point.’
    • ‘The horopter is a curved line which represents the points which are the same distance from the observer as the object of focus.’
    • ‘It can easily be shown that this theoretical longitudinal horopter is a circle, passing through the two eyes and the fixation point.’
    • ‘The difference you notice in your ability to read the brochure is caused by the vertical horopter.’


Early 18th century: from Greek horos ‘limit’ + optēr ‘person who looks’.