Monocular vision

Last updated December 19, 2024

Monocular vision is vision using only one eye. It is seen in two distinct categories: either a species moves its eyes independently, or a species typically uses two eyes for vision, but is unable to use one due to circumstances such as injury.^[1]

In human species

Monocular vision [[Visual perception|is known as seeing and using only one eye in the human species. Depth perception in monocular vision is reduced compared to binocular vision, but still is active primarily due to accommodation of the eye and motion parallax. The word monocular comes from the Greek root, mono for single, and the Latin root, oculus for eye.

Bimonocular vision, also named two-eyed monocular vision, is known as seeing and using both eyes in a monocular way independently of each other without fusion over the entire field of view without visual field loss in the human species^{[ citation needed ]} and was discovered in 2018.^{[ citation needed ]} The word monocular comes from the Greek root, mono for single, and the Latin root, oculus for eye.^{[ citation needed ]}

In animals

The eyes of an animal with monocular vision are positioned on opposite sides of the animal's head, giving it the ability to see two objects at once. This is usually most commonly seen with prey animals, as the reason why their eyes are placed on either side of their head is to make it easier for them to look out for predators, which usually have forward-facing eyes to make it easier to find prey. However, there are some exceptions to this rule, usually if the predator is an animal that is often preyed upon by a greater predator (because of this, apex predators usually tend to have forward-facing eyes) or sport an anatomy that makes it very difficult for it to see straight, such as a short, stiff neck that would limit its head movement, and therefore would require its eyes to be on either side (this is often seen with marine predators such as sharks and killer whales).

Notably, hammerhead sharks have some binocular vision as well as some amount of monocular vision.

Related medical conditions

Monocular vision impairment refers to having no vision in one eye with adequate vision in the other.^[2]

Monopsia is a medical condition in humans who cannot perceive depth even though their two eyes are medically normal, healthy, and spaced apart in a normal way. Vision that perceives three-dimensional depth requires more than parallax. In addition, the resolution of the two disparate images, though highly similar, must be simultaneous, subconscious, and complete. (After-images and "phantom" images are symptoms of incomplete visual resolution, even though the eyes themselves exhibit remarkable acuity.) A feature article in The New Yorker magazine published in early 2006 dealt with one individual in particular, who, learning to cope with her disability, eventually learned how to see three-dimensional depth in her daily life. Medical tests are available for determining monoptic conditions in humans.^[3]

Monocular cues

Monocular cues provide depth information when viewing a scene with one eye.

Accommodation – This is an oculomotor cue for depth perception. When we try to focus on distant objects, the ciliary muscles relax allowing the eye lens to flatten, making it thinner. The kinesthetic sensations of the contracting and relaxing ciliary muscles (intraocular muscles) are sent to the visual cortex where it is used for interpreting distance/depth.
Motion parallax – When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance. If information about the direction and velocity of movement is known, motion parallax can provide absolute depth information.^[4] This effect can be seen clearly when driving in a car nearby things pass quickly, while distant objects appear stationary. Some animals that lack binocular vision because of the wide placement of the eyes employ parallax more explicitly than humans for depth cueing (e.g., some types of birds, which bob their heads to achieve motion parallax, and squirrels, which move in lines orthogonal to an object of interest to do the same).¹
Depth from motion – One form of depth from motion, kinetic depth perception, is determined by dynamically changing object size. As objects in motion become smaller, they appear to recede into the distance; objects in motion that appear to be getting larger seem to be coming closer. Using kinetic depth perception enables the brain to calculate time-to-crash (aka time-to-collision or time-to-contact – TTC) at a particular velocity. When driving, one is constantly judging the dynamically changing headway (TTC) by kinetic depth perception.
Perspective – The property of parallel lines converging at infinity allows us to reconstruct the relative distance of different parts of a scene, or of landscape features.
Relative size – If two objects are known to be the same size (e.g. two trees) but their absolute size is unknown, relative size cues can provide information about the relative depth of the two objects. If one appears larger than the other, the object which appears larger appears to be closer.
Familiar size – Since the visual angle of an object projected onto the retina decreases with distance, this information can be combined with previous knowledge of the objects size to determine the absolute depth of the object. For example, people are generally familiar with the size of an average automobile. This prior knowledge can be combined with information about the angle it subtends on the retina to determine the absolute depth of an automobile in a scene.
Aerial perspective – Owing to light scattering by particles in the atmosphere, objects at a distance have lower luminance contrast and lower color saturation. In computer graphics, this is called "distance fog". The foreground has high contrast; the background has low contrast. Objects differing only in their contrast with a background appear to be at different depths.^[5] The colors of distant objects are also shifted toward the blue end of the spectrum (e.g., distance mountains). Some painters, notably Cézanne, employ "warm" pigments (red, yellow and orange) to bring features towards the viewer, and "cool" ones (blue, violet, and blue-green) to indicate the part of a form that curves away from the picture plane.
Occlusion (also referred to as interposition) – Occlusion (blocking the sight) of objects by others is also a clue which provides information about relative distance. However, this information allows the observer to assess only relative distance.
Peripheral vision – At the outer extremes of the visual field, parallel lines become curved, as in a photo taken through a fish-eye lens. This effect, although usually eliminated from both art and photos by the cropping or framing of a picture, greatly enhances the viewer's sense of being positioned within a real, three-dimensional space. (Classical perspective has no use for this "distortion", although in fact the "distortions" strictly obey optical laws and provide perfectly valid visual information, just as classical perspective does for the part of the field of vision that falls within its frame.)
Texture gradient – Suppose you are standing on a gravel road. The gravel near you can be clearly seen in terms of shape, size and color. As your vision shifts towards the more distant part of the road it becomes progressively less easy to distinguish the texture.

Recent advances in computational machine learning now allow monocular depth for an entire scene to be algorithmically estimated from a single digital image by implicitly using one or more of these cues.^[6]^[7]

Balance

Vision has been known to play an important role in balance and postural control in humans, along with proprioception and vestibular function. Monocular vision affects how the brain perceives its surroundings by decreasing the available visual field, impairing peripheral vision on one side of the body, and compromising depth perception, all three of which are major contributors to the role of vision in balance.^[8]^[9] Studies comparing monocular vision to binocular (two eyes) vision in cataract patients (pre and post surgery),^[10] glaucoma patients (compared with healthy age matched controls),^[11] and in healthy adults and children (in both binocular and monocular conditions)^[8] have all shown to negatively impact balance and postural control than when both eyes are available. Each of the studied populations still displayed better balance when having only one eye compared to having both eyes closed.

In popular culture

There are many examples of mythological creatures that have one eye, and thereby monocular vision.

A popular mythical beast with monocular vision is a cyclops.

Related Research Articles

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects, so parallax can be used to determine distances.

Forced perspective is a technique that employs optical illusion to make an object appear farther away, closer, larger or smaller than it actually is. It manipulates human visual perception through the use of scaled objects and the correlation between them and the vantage point of the spectator or camera. It has uses in photography, filmmaking and architecture.

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 animal has eyes on opposite sides of its head and shares no field of view between them, like in some animals.

Stereoscopy is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. The word stereoscopy derives from Greek στερεός (stereos) 'firm, solid' and σκοπέω (skopeō) 'to look, to see'. Any stereoscopic image is called a stereogram. Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope.

Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions

The visual system is the physiological basis of visual perception. The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. The visual system is associated with the eye and functionally divided into the optical system and the neural system.

An autostereogram is a two-dimensional (2D) image that can create the optical illusion of a three-dimensional (3D) scene. Autostereograms use only one image to accomplish the effect while normal stereograms require two. The 3D scene in an autostereogram is often unrecognizable until it is viewed properly, unlike typical stereograms. Viewing any kind of stereogram properly may cause the viewer to experience vergence-accommodation conflict.

Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye influence the sharpness of an image on its retina. Neural factors include the health and functioning of the retina, of the neural pathways to the brain, and of the interpretative faculty of the brain.

A random-dot stereogram (RDS) is stereo pair of images of random dots that, when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth due to stereopsis, with objects appearing to be in front of or behind the display level.

Stereopsis is the component of depth perception retrieved through binocular vision. Stereopsis is not the only contributor to depth perception, but it is a major one. Binocular vision happens because each eye receives a different image because they are in slightly different positions in one's head. These positional differences are referred to as "horizontal disparities" or, more generally, "binocular disparities". Disparities are processed in the visual cortex of the brain to yield depth perception. While binocular disparities are naturally present when viewing a real three-dimensional scene with two eyes, they can also be simulated by artificially presenting two different images separately to each eye using a method called stereoscopy. The perception of depth in such cases is also referred to as "stereoscopic depth".

Infant vision concerns the development of visual ability in human infants from birth through the first years of life. The aspects of human vision which develop following birth include visual acuity, tracking, color perception, depth perception, and object recognition.

In perceptual psychology, a sensory cue is a statistic or signal that can be extracted from the sensory input by a perceiver, that indicates the state of some property of the world that the perceiver is interested in perceiving.

Binocular disparity refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes' horizontal separation (parallax). The mind uses binocular disparity to extract depth information from the two-dimensional retinal images in stereopsis. In computer vision, binocular disparity refers to the difference in coordinates of similar features within two stereo images.

<span class="mw-page-title-main">Equine vision</span> Eyesight capabilities of horses

The equine eye is one of the largest of any land mammal. Its visual abilities are directly related to the animal's behavior; for example, it is active during both day and night, and it is a prey animal. Both the strengths and weaknesses of the horse's visual abilities should be taken into consideration when training the animal, as an understanding of the horse's eye can help to discover why the animal behaves the way it does in various situations.

The neural basis of prey detection, recognition, and orientation was studied in depth by Jörg-Peter Ewert in a series of experiments that made the toad visual system a model system in neuroethology. He began by observing the natural prey catching behavior of the common European toad.

Chromostereopsis is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images, usually of red–blue or red–green colors, but can also be perceived with red–grey or blue–grey images. Such illusions have been reported for over a century and have generally been attributed to some form of chromatic aberration.

Wiggle stereoscopy is an example of stereoscopy in which left and right images of a stereogram are animated. This technique is also called wiggle 3-D, wobble 3-D, wigglegram, or sometimes Piku-Piku.

<span class="mw-page-title-main">Chameleon vision</span> Visual sense in the family of reptiles

The chameleon is among the most highly visually-oriented lizards, using this sense in prey capture, mating behavior, and predator avoidance. Unique features of chameleon vision include a negative lens, a positive cornea, and monocular focusing. The development of the chameleon visual system could have evolved to aid in prey capture and/or in predator avoidance.

Binocular neurons are neurons in the visual system that assist in the creation of stereopsis from binocular disparity. They have been found in the primary visual cortex where the initial stage of binocular convergence begins. Binocular neurons receive inputs from both the right and left eyes and integrate the signals together to create a perception of depth.

Stereoscopic motion, as introduced by Béla Julesz in his book Foundations of Cyclopean Perception of 1971, is a translational motion of figure boundaries defined by changes in binocular disparity over time in a real-life 3D scene, a 3D film or other stereoscopic scene. This translational motion gives rise to a mental representation of three dimensional motion created in the brain on the basis of the binocular motion stimuli. Whereas the motion stimuli as presented to the eyes have a different direction for each eye, the stereoscopic motion is perceived as yet another direction on the basis of the views of both eyes taken together. Stereoscopic motion, as it is perceived by the brain, is also referred to as cyclopean motion, and the processing of visual input that takes place in the visual system relating to stereoscopic motion is called stereoscopic motion processing.

References

↑ "Monocular vision". Biology Articles, Tutorials & Dictionary Online. 2019-10-07. Retrieved 2023-09-22.
↑ "Monocular Vision Impairment (MVI)". www.guidedogsqld.com.au. Archived from the original on December 8, 2006.
↑ Monocular individuals face increased challenges with driving. These specifically relate to depth perception and peripheral vision. Keeney, et al.,^{[ full citation needed ]} state, "nationwide, monocularly impaired individuals have seven times more accidents than the general population with which they were compared." He recommends monocularly impaired drivers be denied class 1 licenses, (commercial driver license for transport of people), and that they be warned by their doctors regarding increased risk of accident with driving
↑ Ferris, S. H. (1972). Motion parallax and absolute distance. Journal of experimental psychology, 95(2), 258--63.
↑ O’Shea, R. P., Blackburn, S. G., & Ono, H. (1994). Contrast as a depth cue ^{[ dead link ‍]}. Vision Research, 34, 1595-1604.
↑ Godard, C., Mac Aodha, O., Brostow, G.J. (2017). "Unsupervised monocular depth estimation with left-right consistency" (PDF). Proc. Computer Vision and Pattern Recognition. Vol. 2. p. 7.{{cite book}}: CS1 maint: multiple names: authors list (link)
↑ Atapour-Abarghouei, A., Breckon, T.P. (2018). "Real-Time Monocular Depth Estimation using Synthetic Data with Domain Adaptation" (PDF). Proc. Computer Vision and Pattern Recognition. IEEE. pp. 1–8. Retrieved 9 August 2018.{{cite book}}: CS1 maint: multiple names: authors list (link)
1 2 Berela, J. et al. (2011) Use of monocular and binocular visual cues for postural control in children. Journal of Vision. 11(12):10, 1-8
↑ Wade, M. and Jones, G. (1997) The role of vision and spatial orientation in the maintenance of posture. Physical Therapy. 77, 619-628
↑ Schwartz, S. et al. (2005) The effect of cataract surgery on postural control. Investigative Ophthalmology and Visual Science. 46(3), 920-924
↑ Shabana, N, et al. (2005) Postural Stability in primary open angle glaucoma. Clinical and Experimental Ophthalmology. 33, 264-273

External links

George Goober: Living with one eye, British Medical Journal, Volume 282, 20 June 1981, pages 2042−2043 (online)
"Lost Eye" - includes discussion forum and links to support groups
Mind Map: Adjusting and Adapting to Eye Loss
Monocular Giants

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[1] "Monocular vision". Biology Articles, Tutorials & Dictionary Online. 2019-10-07. Retrieved 2023-09-22.

[2] "Monocular Vision Impairment (MVI)". www.guidedogsqld.com.au. Archived from the original on December 8, 2006.

[3] Monocular individuals face increased challenges with driving. These specifically relate to depth perception and peripheral vision. Keeney, et al.,^{[ full citation needed ]} state, "nationwide, monocularly impaired individuals have seven times more accidents than the general population with which they were compared." He recommends monocularly impaired drivers be denied class 1 licenses, (commercial driver license for transport of people), and that they be warned by their doctors regarding increased risk of accident with driving

[4] Ferris, S. H. (1972). Motion parallax and absolute distance. Journal of experimental psychology, 95(2), 258--63.

[5] O’Shea, R. P., Blackburn, S. G., & Ono, H. (1994). Contrast as a depth cue ^{[ dead link ‍]}. Vision Research, 34, 1595-1604.

[godard2017unsupervised-6] Godard, C., Mac Aodha, O., Brostow, G.J. (2017). "Unsupervised monocular depth estimation with left-right consistency" (PDF). Proc. Computer Vision and Pattern Recognition. Vol. 2. p. 7.{{cite book}}: CS1 maint: multiple names: authors list (link)

[abarghouei18monocular-7] Atapour-Abarghouei, A., Breckon, T.P. (2018). "Real-Time Monocular Depth Estimation using Synthetic Data with Domain Adaptation" (PDF). Proc. Computer Vision and Pattern Recognition. IEEE. pp. 1–8. Retrieved 9 August 2018.{{cite book}}: CS1 maint: multiple names: authors list (link)

[Berela-8] 1 2 Berela, J. et al. (2011) Use of monocular and binocular visual cues for postural control in children. Journal of Vision. 11(12):10, 1-8

[9] Wade, M. and Jones, G. (1997) The role of vision and spatial orientation in the maintenance of posture. Physical Therapy. 77, 619-628

[10] Schwartz, S. et al. (2005) The effect of cataract surgery on postural control. Investigative Ophthalmology and Visual Science. 46(3), 920-924

[11] Shabana, N, et al. (2005) Postural Stability in primary open angle glaucoma. Clinical and Experimental Ophthalmology. 33, 264-273

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