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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Binocular vision | 1/6 | https://en.wikipedia.org/wiki/Binocular_vision | reference | science, encyclopedia | 2026-05-05T15:53:38.467964+00:00 | kb-cron |
Within the science of vision, binocular vision focuses on the question of how humans and animals perceive the world with two eyes instead of one. Two main areas are distinguished: directional vision and depth perception (stereopsis). In addition, both eyes can positively or negatively influence each other's vision through binocular interaction. In medical science, binocular vision refers to binocular vision disorders and tests and exercises to improve binocular vision. In biology, binocular vision refers to the fact that the placement of the eyes affects the capabilities of depth perception and directional vision in animals. In society, binocular vision refers to applications for seeing stereoscopic images and aids for binocular vision.
== Directional vision == In the classical science of vision, directional vision describes that when a point of the retina is stimulated by light, this not only leads to a light sensation (image), but also a directional sensation that is recorded by the brain in one combined image of both eyes, as a direction in which the observer is central (egocentric direction).
== Depth vision ==
Depth perception focuses on the question of how the brain uses the difference in perspective between the two eyes to recognise shapes and objects, to see through camouflage, and to gather information about spatial relationships. The main article on stereopsis discusses the qualities of depth perception, the area of space they cover, and how the observer controls the input through attention and eye movements.
== Binocular interaction == Binocular interaction occurs when there is an interaction between the two eyes, which causes vision with both eyes to be different than with one eye alone. Vision can be better (binocular summation) or worse (binocular inhibition).
=== Binocular summation ===
In binocular summation, the signals from both eyes reinforce each other so that visual acuity, contrast sensitivity, flicker sensitivity, and brightness sensitivity improve. Maximum binocular summation occurs when the sensitivities of each eye are equal. Differences in sensitivity decrease the effect of binocular summation. The effect of binocular summation decreases with age.
=== Binocular inhibition === In binocular inhibition, vision with both eyes is worse than with one eye. This can occur with strabismus or a lazy eye, because the weaker eye interferes with the stronger one. Eye dominance, where the image produced by one eye in the brain can suppress the other, is a form of binocular inhibition.
== Perception systems == Information processing for direction perception and depth perception takes place in two systems. One system specializes in color and fine detail and is concerned with discovering shapes and objects in a relatively static environment. The other system specializes in discovering spatial relationships in a rapidly changing environment. The first system contributes to the perception of fused images with fine depth information. The second system contributes to the perception of double images that quickly cover large distances in space and in which the coarse location is the most important information.
== Disorders and tests == About 80% of people can see depth, but not all can do so equally well. Several tests can determine how well someone sees depth, and there are exercises to improve depth perception. If one eye does not function properly or is blind, this can cause stereoblindness, a complete lack of depth perception. There are other eye disorders that can affect binocular vision. For example, sometimes the eye muscles do not work properly, causing the images from both eyes to be misaligned. Another example is where one eye is dominant, so that the signals from the other eye do not come through in the binocular image, or so that the direction in which an object is seen changes. If eye dominance is noticed in time, an attempt can be made to reduce it through exercise, for example, by temporarily taping the dominant eye.
=== Prevalence === Binocular vision abnormalities are among the most common visual disorders. They are usually accompanied by symptoms such as headache, eye strain, eye pain, blurred vision, and occasionally diplopia (double vision). Approximately 20% of patients who come to an optometry clinic have binocular vision defects. As the use of digital aids becomes more common, many children use them for a significant period of time. This can lead to various binocular vision defects, such as reduced accommodative amplitudes, accommodative powers, and positive fusional convergence, both near and far. The most effective way to diagnose visual defects is with the near point of convergence (NPC) test. During the NPC test, a target, such as a finger, is brought to the face until the examiner notices that one eye is turned outward and/or the person has experienced double vision. Binocular defects can be compensated for to some extent by adaptations of the visual system. However, if the deviations of binocular vision are too great (for example, if the visual system has to adapt to excessive horizontal, vertical, torsional or size (aniseikonic) deviations), the eyes tend to avoid binocular vision, which eventually causes or worsens squint.
=== Lazy eye ===
Lazy eye or amblyopia is a neurovisual developmental disorder. The condition is characterized by underdevelopment of several visual features and skills such as visual acuity, eye movements, eye teamwork and binocular depth perception.
=== Squint ===
Squint or strabismus is an eye condition in which the eyes do not look in the same direction. It has long been known that full binocular vision, including stereopsis, is an important factor in stabilizing the postoperative outcome of strabismus corrections. Many people with a lack of stereopsis have (or had) visible strabismus, which has a potential socioeconomic impact on children and adults. Both wide-angle and narrow-angle strabismus, in particular, can negatively impact self-confidence because it disrupts normal eye contact, often leading to embarrassment, anger, and feelings of discomfort (see psychosocial effects of strabismus).
=== Aniseikonia ===
Aniseikonia is an ocular condition where there is a significant difference in the size of the retinal images of the two eyes caused by differences in refraction between the eyes.