Suppression of an eye is a subconscious adaptation by a person's brain to eliminate the symptoms of disorders of

binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...

such as

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

convergence insufficiency Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence. Symptoms The symptoms and signs associated with con ...

and

aniseikonia Aniseikonia is an ocular condition where there is a significant difference in the perceived size of images. It can occur as an overall difference between the two eyes, or as a difference in a particular meridian. If the ocular image size in both e ...

. The brain can eliminate double vision by ignoring all or part of the image of one of the eyes. The area of a person's visual field that is suppressed is called the suppression scotoma (with a

scotoma A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision. Every normal mam ...

meaning, more generally, an area of partial alteration in the visual field). Suppression can lead to amblyopia.

Effect

Nobel-prize winner

David H. Hubel David Hunter Hubel (February 27, 1926 – September 22, 2013) was a Canadian American neurophysiologist noted for his studies of the structure and function of the visual cortex. He was co-recipient with Torsten Wiesel of the 1981 Nobel Pri ...

described suppression in simple terms as follows: :"Suppression is familiar to anyone who has trained himself to look through a monocular microscope, sight a gun, or do any other strictly one-eye task, with the other eye open. The scene simply disappears for the suppressed eye."

: ''Eye, Brain, and Vision'', Chapter 9 "Deprivation and development"
section "Strabismus"
Published online by Harvard Medical School (downloaded 30 September 2014) Suppression is frequent in children with

anisometropia Anisometropia refers to a condition when two eyes have unequal refractive power. Generally, a difference in power of one diopter (1D) or more is the accepted threshold to label the condition anisometropia. Patients can tolerate 3 D of anisomet ...

or both. For instance, children with infantile esotropia may alternate with which eye they look, each time suppressing vision in the other eye.

Measurement

During an

eye examination An eye examination is a series of tests performed to assess vision and ability to focus on and discern objects. It also includes other tests and examinations pertaining to the eyes. Eye examinations are primarily performed by an optometrist, ...

, the presence of suppression and the size and location of the suppression scotoma may be the Worth 4 dot test (a subjective test that is considered to be the most precise suppression test), or with other subjective tests such as the Bagolini striated lens test, or with objective tests such as the 4 prism base out test.

Anti-suppression therapy

Suppression may treated with

vision therapy Vision therapy (VT), or behavioral optometry, is an umbrella term for alternative medicine treatments using eye exercises, based around the pseudoscientific claim that vision problems are the true underlying cause of learning disabilities, parti ...

, though there is a wide range of opinions on long-term effectiveness between eye care professionals.

Age factors

Young children with strabismus normally suppress the visual field of one eye (or part of it), whereas adults who develop strabismus normally do not suppress and therefore suffer from double vision (

diplopia Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

). This also means that adults (and older children) have a higher risk of post-operative diplopia after undergoing strabismus surgery than young children. Patients who have undergone strabismus surgery at a young age often have monofixation syndrome (with peripheral binocular fusion and a central suppression scotoma).

References

{{reflist * Carlson, NB, et al. ''Clinical Procedures for Ocular Examination. Second Ed.'' Mc Graw-Hill. New York 1996. Human eye Binocular rivalry

Effect

Measurement

Anti-suppression therapy

Age factors

See also

References