deviating eye
The deviating eye is the eye in a manifest strabismus whose visual axis is not directed at the object of regard, with the fellow eye fixating.1,2 In a heterotropia, the visual axes do not intersect at the point of fixation.1
The image from the deviating eye causes double vision or, more commonly in children, is suppressed at the cortical level. Central suppression inhibits the image from the fovea of the deviating eye to avoid confusion, and peripheral suppression inhibits the image from its peripheral retina to eliminate diplopia. Constant suppression of the same deviating eye leads to amblyopia, while alternating suppression makes amblyopia less likely. In anomalous retinal correspondence, the fovea of the fixating eye pairs with a non-foveal point of the deviated eye, allowing some anomalous binocular vision.1
On the cover test, the examiner covers the fixing eye and watches the deviating eye move to take up fixation. Adduction of the deviating eye indicates an exotropia, abduction an esotropia, downward movement a hypertropia, and upward movement a hypotropia.1
More detail
When the cover-uncover test finds a constant tropia, both a primary and a secondary deviation are measured. The primary deviation is measured with the usually fixating eye on the target and the prism over the deviating eye, and the secondary deviation with the usually deviating eye on the target and the prism over the usually fixating eye. A difference of 5 prism diopters or more between the two measurements indicates a noncomitant deviation.2
Sources (5)
- Kanski, Clinical Ophthalmology (2024), ch. 18
- Carlson and Kurtz, Clinical Procedures for Ocular Examination, ch. 2
- Noorden, G. K. V., & Campos, E. C. (2002). Binocular vision and ocular motility: Theory and management of strabismus. Mosby.
- Kushner, B. J. (2017). Strabismus. In W. Tasman & E. A. Jaeger (Eds.), Duane's Ophthalmology (2017 ed.). Lippincott Williams & Wilkins.
- Remington, L. A. (2012). Clinical anatomy and physiology of the visual system. Elsevier Health Sciences.
Reviewed October 2026