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Donder’s Phaenophthalmotrop


A brass instrument supported by a metal tripod base. The top element consists of a sphere that rotates on three axes. Each axis has a dial with four measurement quadrants, each marked 0-90 degrees. A fourth dial rests on a central optical piece at the centre of the sphere. This dial is connected to two antenna-like rods. The lens is removable. An optical chamber (camera obscura) runs through the centre of the sphere.

Accession Number: 2012.psy.81

Alternative Name: Ophthalmotrop

Primary Materials: Brass, Metal


Dimensions (cm): Height = 59, Width (Diameter) = 24


This instrument demonstrates and quantifies one element of the mechanics of the human gaze, specifically the phenomenon of “pseudotorsion”: the torsion of the visual axes in the “tertiary positions of gaze” (right-up, right-down, left-up, or left-down) relative to a grid.

Condition: Good

Associated Instruments:

Manufacturer: Spindler & Hoyer, Germany

Date of Manufacture: c. 1921


Department of Psychology, University of Toronto

Additional Information and References:

Historical Notes:

In 1846, Franciscus Cornelis Donders (1818-1889), at Dutch professor of Physiology, published a paper on eye muscle mechanics where he noted that the torsion of the visual field depended upon the amount of elevation or depression of the right or left gaze (pseudotorsion.) [Simonsz and den Tonkelaar, 96]

1) Simonsz, H. J., and I. Tonkelaar. 1990. 19th century mechanical models of eye movements, donders’ law, listing’s law and helmholtz’ direction circles. <i>Documenta Ophthalmologica</i> 74 (1): 95-112.

2)Wikipedia contributors, <a href=” “>”Franciscus Donders,”</a> <i>Wikipedia, The Free Encyclopedia</i>,(accessed February 10, 2012).