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Stereopsis and Amblyopia

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Amblyopia is an important vision condition since it is one of a leading cause of visual loss in infants and young children. It reflects the neurological damage that arises when normal visual development is disrupted.

Amblyopia is a condition that provokes professionals to understand when and how brain plasticity can be used to restore visual functions. In this blog post, we will explore stereopsis and amblyopia, and their connection. We are going to focus on stereopsis, i.e., the perception of depth and three-dimensional structure through binocular vision and the possibilities for recovery of it.

Binocular Vision

Binocular vision refers to the ability of humans and some other animals to perceive depth and three-dimensional (3D) visual information by combining the images seen by each eye.

It is the coordinated use of both eyes to create a single, unified perception of the visual world. Binocular vision allows us to have a sense of depth and perceive objects in three dimensions.

What is Stereopsis?

Stereopsis, on the other hand, is a specific aspect of binocular vision. Put simply, is the ability of our brain to perceive depth by processing the slightly different images received by each eye. It’s a phenomenon that relies on binocular vision—the coordination between both eyes to create a single, unified perception of the world.

Our eyes have a slight separation, which results in each eye seeing a slightly different view of the world. Stereopsis occurs when the brain processes these differences and merges the two images into a single perception that includes depth and 3D information.

Imagine holding a finger in front of your face and alternately closing each eye. Notice how the position of your finger seems to shift against the background. This apparent shift is due to the parallax— the slight difference in perspective—observed by each eye.

Stereopsis capitalizes on this difference, allowing our brain to compute the spatial relationships between objects and gauge their distance from us.

The Importance of Stereopsis

Stereopsis is not merely a fascinating quirk of human vision; it’s an essential aspect of our daily functioning. Consider tasks like driving, catching a ball, or pouring a glass of water—each relies heavily on our ability to accurately judge distances and perceive spatial relationships. Without stereopsis, these activities would be far more challenging, if not impossible.

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Moreover, stereopsis plays a crucial role in the development of our visual system. In infancy, the brain undergoes a process known as visual maturation, during which it learns to coordinate input from both eyes and refine its ability to perceive depth. Adequate stereopsis during this critical period is crucial for the development of spatial awareness and hand-eye coordination

Challenges with Stereopsis

While stereopsis is a remarkable feat of nature, it’s not without its challenges. Certain vision conditions, such as strabismus (misaligned eyes) and amblyopia (lazy eye), can disrupt binocular vision and impair stereopsis. . Additionally, age-related changes in vision, such as presbyopia, can diminish the brain’s ability to integrate visual information effectively.

Furthermore, the rise of digital devices and prolonged near work has raised concerns about the potential impact on stereopsis and overall visual development, particularly in children. Researchers continue to explore the relationship between screen time, binocular vision, and stereopsis to better understand the long-term consequences.

Poor Stereopsis Treatment

Certainly, the rehabilitation of stereopsis, or depth perception, often necessitates a comprehensive, binocular approach. Here’s why:

  1. Binocular Vision Integration: Stereopsis relies on the integration of visual information from both eyes. In cases where stereopsis is impaired, it’s crucial to address the underlying issues that affect binocular vision coordination.
  2. Targeting Both Eyes: Since stereopsis involves the brain’s ability to combine images from each eye into a single three-dimensional perception, treatments should target both eyes simultaneously to promote binocular cooperation and synchronization.

Connection Between Stereopsis and Amblyopia

Amblyopia has a significant influence on visual motor activities and sports performance in children. Under binocular viewing conditions, the most prevalent defect associated with amblyopia is impaired stereoscopic depth perception. What is more, stereopsis is more impacted in strabismic than in anisometropic amblyopia.

Treating Amblyopia

There are various approaches to treating amblyopia (patching, perceptual learning, games), both in anisometropic and strabismic amblyopes.

However, recovery of stereopsis may require more active treatment in strabismic than in anisometropic amblyopia. Individuals with strabismic amblyopia have a very low probability of improvement with monocular training.

Why does Stereopsis Matter in Amblyopia Treatment?

Stereoscopic disparities strongly contribute to depth and shape perception when presented in conjunction with other depth cues. Studies found that there is a correlation between stereopsis acuity and driving performance.

Moreover, amblyopes with poor stereopsis have visual-guided hand movement impairments identical to those generated by occluding vision in one eye in normally sighted participants, according to a number of studies.

Bad driving can be the result of poor stereopsis.
Bad driving performance may result from poor stereopsis

Poor stereopsis, rather than lower visual acuity, fixation instability, or impaired vergence control, is considered to be the cause of these deficiencies.

In addition, poor stereoacuity in amblyopic individuals appears to hinder visual feedback control of motions, leading to much longer and less precise hand movements.

Losing stereopsis has consequences that go beyond hand motions. Without stereopsis, adaptations to change in terrain (e.g. steps) are significantly less accurate, both in normally sighted monocular individuals and in persons with amblyopia and reduced stereoacuity or no stereopsis.

Connection Between Stereopsis and Amblyopia: Key Findings

  1. Impaired stereopsis is very common deficit associated with amblyopia.
  2. Impaired stereopsis may have a substantial impact on visuomotor tasks.
  3. Impaired stereopsis may also limit career options for adults with amblyopia.

Conclusion

Stereopsis is a fundamental aspect of human vision that shapes how we perceive and interact with the world. By combining the images from each eye, our brain creates a detailed picture of depth and distance. Taking care of our eyes through regular check-ups and activities that promote good vision helps us preserve this incredible ability.

Frequently Asked Questions

What is stereopsis?

Stereopsis is a specific aspect of binocular vision. It is the ability to perceive depth and perceive objects in 3D by comparing the slightly different images seen by each eye.

What is connection between stereopsis and amblyopia?

Under binocular viewing conditions, the most prevalent defect associated with amblyopia is impaired stereoscopic depth perception.

Why does stereopsis matter?

Stereoscopic disparities strongly contribute to depth and shape perception when presented in conjunction with other depth cues.

Source: Levi, D. M., Knill, D. C., & Bavelier, D. (2015). Stereopsis and amblyopia: A mini-review. Vision Research, 114, 17–30. https://doi.org/10.1016/j.visres.2015.01.002

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