Fixation disparity is a tendency of the eyes to drift in the direction of the heterophoria. While the heterophoria refers to a fusion-free vergence state, the fixation disparity refers to a small misalignment of the visual axes when both eyes are open in an observer with normal fusion and binocular vision.[1] The misalignment may be vertical, horizontal or both. The misalignment (a few minutes of arc) is much smaller than that of strabismus. While strabismus prevents binocular vision, fixation disparity keeps binocular vision, however it may reduce a patient's level of stereopsis. A patient may have a different fixation disparity at distance than near. Observers with a fixation disparity are more likely to report eye strain in demanding visual tasks; therefore, tests of fixation disparity belong to the diagnostic tools used by eye care professionals:[2][3][4][5][6] remediation includes vision therapy, prism eye glasses, or visual ergonomics at the workplace.
^Eskridge, JB; Amos, JF; Bartlett, JD (1991). Clinical procedures in Optometry. New York: Lippincott Co.
^Scheiman, Mitchell (4 October 2019). Clinical management of binocular vision : heterophoric, accommodative, and eye movement disorders. Wick, Bruce (Fifth ed.). Philadelphia. ISBN978-1-4963-9973-1. OCLC1098229972.{{cite book}}: CS1 maint: location missing publisher (link)
^Evans, Bruce J. W. (2007). Pickwell's binocular vision anomalies. Pickwell, David. (5th ed.). Edinburgh: Elsevier Butterworth Heinemann. ISBN978-0-7020-3925-6. OCLC785829294.
^Schroth, Volkhard. (2012). Binocular correction : aligning prisms according to the Haase approach (2. ed.). [Heemskerk]: Zijdar Books. ISBN978-90-78376-09-5. OCLC835292953.
^Jaschinski, Wolfgang (2002). "The Proximity-Fixation-Disparity Curve and the Preferred Viewing Distance at a Visual Display as an Indicator of Near Vision Fatigue". Optometry and Vision Science. 79 (3): 158–169. doi:10.1097/00006324-200203000-00010. ISSN1040-5488. PMID11913842. S2CID2793623.