Exercises for binocular vision at home

What is stereopsis?

La binocular vision or facilitated vision is the process by which we can perceive what surrounds us in three dimensions, experiencing a sensation of depth, distance or proximity of each of the objects. This process occurs through a mechanism called retinal image disparity, which occurs when, thanks to two slightly different images projected in each retina of our eyes, the brain manages to combine both images to create a three-dimensional vision.

Enhanced binocular vision, or stereopsis, is key to many activities of daily living, especially for everyday tasks such as driving a car. However, it is estimated that more than 5% of the population have light or depth vision problems, diagnosis of which is essential to ensure good vision.

Retinal Imbalance Diagram and Stereopsis

Mechanism of binocular vision

The fusion reflex is a fundamental mechanism of binocular vision. In this case, the images that were formed in the retinal plane merge into a single picture with stereoscopic characteristics. This fusion occurs at the level of the cerebral cortex.

For the image to become unified, it is necessary to match the images obtained from the right and left retinas. This takes into account the size and shape of the image, as well as the area where it is projected onto corresponding identical areas of the retina. Each point in the retinal plane has its own corresponding point on the opposite side. Asymmetrical areas are called non-identical points, or disparate. When image points fall into these disparate points of the retinal plane, binocular vision becomes impossible. Instead of merging the image, doubling occurs.

In newly born children, coordinated movement of the eyeballs is not possible, and therefore binocular vision is absent. At about one and a half months, babies develop the ability to fix their gaze with two eyes, and at 3-4 months we can already talk about stable binocular fixation. The fusion reflex is formed only by 5-6 months, and full binocular vision - only by 12 years. In this regard, strabismus is more often present in patients of preschool age.

To form normal binocular vision, several conditions must be met:

• Ability to fusion (bifoveal fusion).
• Coherence in the work of all muscle fibers responsible for eye movement. They should ensure a parallel position of the eyeballs while the patient looks into the distance. When the gaze moves to a closer position, a proportional convergence of the visual axes occurs. This process is called convergence. Also, the extraocular muscles must respond to the associated movements of the eyeballs directed towards the object being studied.
• The visual acuity of each eye should not be less than 0.3-0.4, which is sufficient to form a clear image.
• The eyes should be located in the same horizontal and frontal plane. If, as a result of injury, tumor, inflammation or surgery, a change in symmetry occurs, then the merging of images becomes impossible.
• Images projected onto the retinal plane must be of this size (iseikonia). When the size of objects on the retina is different, we are talking about anisometropia, which occurs when the refraction of the two eyeballs is different. In order for binocular vision to be present, the degree of anisometropia should not exceed 2-3 diopters. This must be taken into account when choosing, despite good visual acuity, binocular vision will be absent.
• Also a necessary condition for binocularity is the transparency of the media of the eye (lens, vitreous body, cornea), the absence of pathological changes in the perceptive apparatus (retina) and the conduction system (optic nerve, optic tract, chiasm, cerebral cortex, subcortical centers).

Why is it important to have good stereoscopic vision?

La Visión binocular o visión estereoscópica

La visión binocular, también conocida como visión estereoscópica, es la capacidad que tiene una persona para integrar dos imágenes, provenientes de cada ojo, en una sola. Seguir leyendo…

">stereoscopic vision This is fundamental in many daily activities, such as playing ball, performing certain sports, activities that require Agudeza visual

La agudeza visual es el valor que nos indica nuestra capacidad para identificar imágenes y poder apreciar detalles y características de las mismas. Seguir leyendo…

“>visual acuity, the use of video games and even our ability to applaud correctly.

However, one task where the ability to perceive depth and distance is more relevant is in driving. binocular vision Relief is fundamental to calculating distances when overtaking or when we draw a curve.

Poor stereopsis can also affect daily work, especially in those professions that require good attention, such as surgeons or those who work with precision machinery, with special attention to those that can cause hand injuries.

Conditions that may affect stereoscopic vision

Stereoscopic vision requires the cooperation of both eyes, requiring that both are aligned and that the vision of each is good. For this reason, patients with certain pathologies that affect the alignment or visual ability of one eye may have compromised stereopsis, which is often seen in patients with:

• Strabismus : Occurs when there is a deviation in the position of the eyes, causing the gaze to point to different points when focusing.
• Blurred eye or amblyopiaThis occurs when usually one eye presents with a delay in the development of visual function. This condition is closely related to Tropias
  Las tropias son una alteración de la visión binocular que provoca la desviación de los ejes oculares, impidiendo que los ojos puedan enfocar al mismo tiempo en un punto determinado.Seguir leyendo…

  ">strabismus, but may also present for other reasons.

Additionally, any other problem that affects the ability of one of the eyes to see correctly, due to injury, trauma, etc., can affect stereoscopic vision, affecting the ability to measure the depth or distance of objects.

How does stereoscopic vision work?

In a healthy eye, incoming light passes through the pupil onto the cornea and lens, from where it is projected through the vitreous body onto the retina. It, in turn, contains nerve endings that perceive objects in two dimensions.

The optic nerve then transmits the received signal from the neurons to the brain, where the nerve impulses are deciphered. Binocular vision allows a person to perceive the following types of information:

• Color;
• Volume;
• Shape;
• Remoteness of the object;
• Qualities of objects (softness/hardness, roughness).

So, the mechanisms of stereoscopic vision are such that it is responsible for assessing the distance to objects, their volume and shape. And if a person loses such vision, it can be dangerous for him: it becomes difficult or impossible for him to determine the distance of a car, stairs, or road. In other words, it is stereoscopic vision that allows you to navigate in space.

Binocular stereoscopic vision is important, for example, when driving a car - it helps to identify an object moving at a higher speed and make the right decision in driving a car. Information that a certain object is in front of another and partially obscures it helps to recognize such an object.

People with impaired stereoscopic vision cannot perform a number of professional functions that require determining the distance to moving objects: police officers, military personnel, athletes, dentists.

Stereoscope test

There are many methods for studying stereopsis, both in children and adults, from cardboard with stereograms, anaglyphs and vectograms and modern stereoscopes for dynamic vision, which we use in driving analysis or in athletes.

Measurement of stereopsis can be performed using a screening test that requires only 1-2 minutes, or a more detailed analysis for special situations. In any case, the ophthalmologist is the one who will decide which test is relevant in each particular case.

The most common stereopsis tests:

Thymus test

Through the use of polarized glasses, which allow the perception of objects at a certain depth, the patient will observe certain images to determine the state of his binocular vision with relief. In this group of tests we find:

• Fly test: used in children, involves asking the child to catch an image of a fly to measure their stereoscopic vision.
• Test animal: also used in children, in which case the patient must indicate which of the three animals in the rows has the relief.
• Checking the Circles: The worksheet has nine numbered diamonds with four circles inside each. The patient must indicate which circle is out of plane in each of the diamonds.

Rando test

It is also performed using polarized glasses. In this case, the patient must detect hidden geometric shapes in a series of images, this test has several levels to determine the patient's visual acuity.

Test E

Like the previous tests, this one also involves the use of polarized glasses. A series of pictures of the letter E is shown, in which the patient must indicate which side the legs of the letter are on in each one.

Steroid test at the optometry department of Área Oftalmológica Avanzada

What is binocular vision?

Binocular vision is one of the most important functions of the visual apparatus. It begins to form in children almost immediately after birth and develops until the age of 12-14 years. A person with stereoscopic vision perceives the world in 3D format, that is, he can not only see the shapes and outlines of objects, their size in width and height, but also approximately determine the distance between them.

Lack of binocular vision leads to many problems. It is difficult for a person to distinguish the distance between objects and navigate in space. In everyday life, this manifests itself in difficulties when trying to pour water into a glass or thread a thread into the eye of a needle. In professional life, problems arise with employment and choice of profession. Thus, impaired binocular vision is a serious limitation for becoming a pilot or driver.

Binocularity disorders can appear at any age and for various reasons. Before we look at these reasons, we need to know how binocular vision works.

Is it possible to improve stereoscopic vision?

This may be the most controversial and at the same time the most important point. Until recently, it was believed that people with changes in stereopsis after the first 2 or 3 years of life failed to achieve significant improvement.

The reality is as it happened with patients with amblyopia or Ambliopía o ojo vago La ambliopía es la pérdida de agudeza visual que se presenta sin ningún tipo de alteración en la estructura ocular. Esta disminución de agudeza visual persiste incluso si la persona utilityiza gafas o lentillas. Seguir leyendo…

“>lazy eye, that it was also thought that they could not improve vision after a period of neuroplasticity between 8 and 9 years, and that we now know that there are methods to restore visual acuity, something similar happens with stereopsis. There are techniques that can stimulate brain cells with other functions to activate via retinal disparity signals, thus restoring stereoscopic vision function.

In the departments of Optometry and Vision and Sports of the Área Oftalmológica Avanzada , we have achieved significant improvements both in people with childhood disorders and in elite athletes who sought to improve their performance with higher-level dynamic stereopsis.

Improvement in stereopsis can be achieved by most people, to varying degrees depending on each case, the most effective patients will be those whose change prevents them from performing precision work or driving safely. We have seen this after cataract surgery or after refractive surgery to correct problems such as myopia. Some stereoscopic vision is lost, in these cases it can be restored and even improved, which is very important for patients of a certain age who want to continue moving.

Finally, those who may benefit most from improved stereoscopic vision are those who participate in sports such as tennis, table tennis, skiing, fencing, and especially all sports such as driving, motorsports, and motorsports.

En Área Oftalmológica Avanzada We have a professional team to determine the status of your stereoscopic vision, visit us and find out how we can help you ensure your visual well-being.

Related articles:

• Mechanism of vision
• Vision Goal
• Vision and attention
• Binocular vision
• 3D Screens and Vision
• Sports vision

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Jesus Marin del Barrio. Director of the Department of Optometry

Optician.
Director of Optometry Department. at Área Oftalmológica Avanzada Optician optometrist specializing in clinical optometry. He is the Clinical Optometry Coordinator for Advanced Ophthalmology. His training includes a Master's in Optometry and Visual Training at the Optometric Specialization Center in Madrid and a Postgraduate in Pediatric Optometry at the Polytechnic University of Catalonia. For more than 10 years he was an assistant professor at the Escola de Terrassa University and was awarded the best oral presentation award at the International Congress of Optometry, Contactology and Ophthalmic Optics held in Madrid in 2008.

Checking stereopsis

Stereopsis testing is a diagnostic study to determine the threshold of spatial vision and identify disparity - the difference in the position of points on the retina relative to each other. The phenomenon represents the basis of psychophysiological processes in the brain responsible for the three-dimensional perception of the world.

Diagnosis is carried out using special devices - Wheatstone stereoscope, phoropter.

A stereoscope is a binocular device in ophthalmology that allows you to individually view three-dimensional images.

Device types:

• episcope or projector - optics that creates a real flat image of an object on a monitor;
• diascope - a device for visualizing transparent slides through light rays projected onto the screen;
• phoropter is an optometric device that measures refractive pathological changes in physiological lenses.

Stereoscopic vision is not always stable. Over time or under the influence of internal and external factors, they change, become unstable or are completely absent.

Not all people perceive the depth of objects with the same accuracy. The level of perception is checked using pictures (stereo pairs).