physiologic diplopia
Physiologic diplopia is the doubling of objects that lie off the horopter, and anyone with normal binocular vision can see it. Points on the horopter stimulate corresponding retinal elements and are seen singly. Points off the horopter are imaged on disparate elements and are seen double.1 The doubling starts only beyond Panum's fusional area, a narrow band in front of and behind the horopter in which disparate images still give single vision.1
An object nearer than the fixation point is imaged in temporal disparity and seen in crossed (heteronymous) diplopia. Shutting the right eye removes the left-hand image. An object farther than the fixation point is imaged in nasal disparity and seen in uncrossed (homonymous) diplopia.1
A patient who suddenly notices physiologic diplopia may seek care for double vision. When no muscle paresis or other cause is found, the doubling is evidence of normal cooperation between the two eyes, and its presence shows that the patient uses both eyes in casual seeing.1
More detail
Physiologic diplopia is a tool in free-space exercises for heterophoria. The patient fixates one of two pencils held on the midline against a plain background and notices the other pencil double, uncrossed for the farther pencil and crossed for the nearer one. Difficulty seeing both images indicates a fairly gross degree of suppression, which usually clears quickly in heterophoria.2
Sources (8)
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 2
- Pickwell's Binocular Vision Anomalies, ch. 10
- Bhola, R. 2006. Binocular Vision. EyeRounds.org. University of Iowa Health Care. [online] Available at: <https://webeye.ophth.uiowa.edu/eyeforum/tutorials/bhola-binocularvision.htm> [Accessed 6 May 2024]. secondary
- Noorden, G.K. and Campos, E.C. 2002. Binocular vision and ocular motility: theory and management of strabismus. 6th ed. St. Louis: Mosby.
- Ogle, K.N. 1964. Researches in binocular vision. New York: Hafner.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Steinman, S.B., Steinman, B.A. and Garzia, R.P. 2000. Foundations of binocular vision: a clinical perspective. New York: McGraw-Hill.
- Webvision. 2005. The Perception of Space. [online] Available at: <https://www.ncbi.nlm.nih.gov/books/NBK11512/> [Accessed 6 May 2024]. secondary
Reviewed October 2026