vectogram
A vectogram is a polarized stereogram made of two cross-polarized images.1 The two targets are polarized at 90° to each other, so a patient wearing properly oriented Polaroid spectacles sees each target with only one eye. The Titmus Stereo Test uses this principle.2
Each sheet carries a picture of the same scene taken from a slightly different angle, and the back-illuminated sheets are placed directly on top of one another. A nonstrabismic patient sees a single picture in three-dimensional relief.3 Variable vectograms come in pairs of slides that differ only in polarization and disparity. Separating the slides horizontally creates a convergence or divergence demand, which vision therapy uses to increase the amplitude of positive and negative fusional vergence.4
More detail
Moving the slide seen by the right eye to the left, and the slide seen by the left eye to the right, creates a convergence demand; reversing the movement stimulates divergence.4 In training, the slide is moved until the patient reports blur, diplopia or suppression, then moved back until binocularity returns, and the cycle is repeated while the patient tries to hold binocularity as long as possible.3 The scale at the bottom of each vectogram gives the prismatic demand for a given separation, and the scale is correct only at a viewing distance of 40 cm.4
Sources (7)
- Pickwell's Binocular Vision Anomalies, glossary
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 15
- Pickwell's Binocular Vision Anomalies, ch. 10
- Scheiman and Wick, Clinical Management of Binocular Vision, ch. 6
- Rutstein, R. and Daum, K. (1997). Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Scheiman, M. and Wick, B. (2014). Clinical Management of Binocular Vision. 4th ed. Philadelphia: Lippincott Williams & Wilkins.
- Steinman, S., Steinman, B. and Garzia, R. (2000). Foundations of Binocular Vision. New York: McGraw-Hill.
Reviewed October 2026