ATROPOPHOROMETER (fig. 1) was devised in 19441 for the purpose of permitting measurements of extraocular muscle anomalies in the six cardinal directions by any of the methods in which a heterotropia or heterophoria is usually measured. The instrument consisted of two lights mounted in such a way that each moved as though it were traveling over the surface of a sphere which had for its center the center of rotation of the eye. In addition, each light was shielded so that it could be seen only by the eye around whose center of rotation the light moved. The distance of the lights from the eye was about 15 inches (38 cm.).
With this instrument the lights were used for fixation while the cover test was being performed; while each eye fixed its corresponding light, the lights were moved manually until, when the cover was passed back and forth from
PUTNAM OA, QUEREAU JVD. THE TROPOPHOROMETERAn Instrument Employing a New System of Coordinates for More Accurate Measurements of Heterophoria and Heterotropia. AMA Arch Ophthalmol. 1951;45(2):186-193. doi:10.1001/archopht.1951.01700010191007