Suppression (Image Suppression)
Suppression is a mechanism in which the brain actively switches off the image coming from one eye, in order to avoid double vision or an image that cannot be merged with the other one.
This is the answer to a question many parents ask themselves: why a child with a squint, or with a large difference in refractive error between the eyes, does not complain of double vision. They do not complain because they do not see double — the brain has solved the problem in its own way, simply by ceasing to use one of the sources.
The solution is effective and immediate, but it comes at a price. The eye whose signal is switched off stops being used, and with that the development of vision in that eye comes to a halt. This is one of the routes by which amblyopia arises.
Suppression is one of the forms of sensory adaptation to a squint — alongside abnormal retinal correspondence and double vision. Its presence and type are assessed in a binocular vision examination, using tests such as the Worth test, the Bagolini test or stereotests.
The most important practical consequence of this mechanism: a child with suppression has no reason whatsoever to report anything. They see singly and sharply — with one eye. This is exactly why the difference is picked up only by an examination in which each eye is checked separately.
Suppression is assessed solely in an examination with a specialist — ocu•vio does not carry one out and does not replace it. If a child is under specialist care, the choice of any home activities is made by the supervising person.
Frequently Asked Questions
Why does a child with a squint not complain of double vision?
Because the brain switches off the image from one eye before double vision arises. The child sees singly and has nothing to report.
What is the risk of the image from one eye being switched off?
The eye whose signal is switched off stops being used, and the development of vision in it comes to a halt. This is one of the routes by which amblyopia arises.
How is the presence of suppression checked?
In a binocular vision examination, using tests such as the Worth test, the Bagolini test or stereotests. It cannot be assessed at home.
Is suppression the only adaptation to a squint?
No — alongside it, abnormal retinal correspondence and double vision are also listed.
Related concepts
Source: Polish Ophthalmological Society, Section of Paediatric Ophthalmology and Strabismus, Wytyczne postępowania w zezie [Guidelines on the management of strabismus], 2021.
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