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Questions and Answers
What is the term for the physical locations, with respect to the observer, of objects in the environment?
What is the term for the perceived locations, with respect to the observer, of objects in the environment?
What is the term for an object viewed by an eye being imaged onto the fovea?
What did Panum (1858) show about fusion (single vision)?
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What did Panum propose regarding binocular single vision?
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What is the function of the horopter in understanding binocular vision processes?
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What happens to objects beyond the limits of Panum’s fusional area?
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What does Hering's Law of Identical Visual Direction state?
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What is the role of the cyclopean eye in binocular vision?
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What is the nature of the horopter based on empirical measurements?
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What is the term for the region in space where there is binocular single vision?
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What is the process that combines the two images from each eye into a single percept?
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What determines the size of the region in space where there is binocular single vision?
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What is the term for the smallest detectable stereoscopic depth?
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What condition is required for stereopsis to occur?
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What is the term for the area where stereoscopic acuity is most acute?
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Which clinical test uses red and green filters to separate images to the two eyes?
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What is the Troxler effect related to in binocular vision?
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What is the result of motion parallax in relation to depth perception?
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What is the primary role of Panum's area in binocular vision?
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What is the term for the area where there is binocular single vision?
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What causes sensory suppression to occur?
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What is the primary requirement for sensory fusion to occur?
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What is the term for the process that combines the two images from each eye into a single percept?
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Which clinical test is commonly used to assess stereopsis?
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Which method is NOT used for suppression testing in eye alignment testing?
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Which test uses real depth elements painted on one surface in squares to create different disparities for testing stereopsis?
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What does the Lang test use to separate the images to each eye for measuring stereopsis?
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Which type of test creates relative retinal disparity by using random-dot patterns?
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Which test uses red/green anaglyphic plates to measure stereoacuity?
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Study Notes
Visual Direction and Correspondence in Binocular Vision
- Each retinal element has its own sense of direction in space, known as retinal local sign.
- Stimulation of the fovea gives rise to the principal visual direction, which is the dominant sense of visual direction.
- Visual localization involves both oculocentric direction (with respect to the fovea) and egocentric direction (with respect to the body).
- Visual information from the retina is integrated with eye movement and body position information in the visual cortex.
- Hering's Law of Identical Visual Direction states that stimulating the fovea in each eye gives the same visual directions.
- Binocular viewing results in identical oculocentric directions from both eyes, leading to the concept of the cyclopean eye.
- The cyclopean eye is an imaginary concept helpful in understanding binocular directions, situated between the two eyes.
- Corresponding retinal points, when stimulated, give rise to the same visual direction and are perceived as single, while non-corresponding points cause double vision.
- The longitudinal horopter represents a map of retinal correspondence in binocular visual space, formed by joining corresponding points in space.
- The geometrical horopter assumes perfect symmetry and spherical eyes, forming a circle known as the Vieth-Muller circle.
- Empirical measurements of the horopter using different criteria show that it is not a perfect circle as predicted from the geometric model.
- The horopter is also measured based on the region of single binocular vision and optimal stereoscopic depth judgements, revealing its non-circular nature.
Binocular Vision and Depth Perception
- Panum’s area for foveal vision at 30cm ranges from 7-12 min arc, while in the periphery at 5° it is about 24-30 min arc, reducing physiological diplopia.
- Fusion of images requires similarity between left and right eye images, and oculomotor response is associated with it.
- Binocular rivalry occurs when dissimilar images are fused, resulting in rhythmic alternation of separate images.
- Suppression is an inter-ocular process of inhibition, preventing double vision, occurring in ocular abnormalities like amblyopia or strabismus.
- Saccadic suppression occurs during rapid eye movements, preventing perception of movement.
- The Troxler effect causes suppression in monocular conditions.
- Monocular cues for depth perception include aerial perspective, light and shade, overlap, geometric perspective, interpretation of size, motion parallax, and stereopsis.
- Aerial perspective results from light scatter in the atmosphere, causing distant objects to appear blurred and more blue.
- Light and shade contribute to depth perception based on the distribution of light and shade, affecting the appearance of objects.
- Overlap cues depth perception, with overlapped objects appearing further away.
- Geometric perspective provides a powerful cue for depth sense, with progressively smaller angles giving the appearance of changes in depth.
- Motion parallax, where closer objects move more quickly than further ones, can be a powerful cue to depth perception, especially with head movements.
Testing for Eye Alignment and Depth Perception
- Eye alignment testing includes measuring differential eye alignment, refractive error, and conditions such as amblyopia and strabismus.
- Suppression testing involves methods such as Worth (4-dot) and variants, Thomson chart variant, red/green methods, polarization methods, and mirror-pola tests.
- Bagolini striated lens is used for suppression testing, which involves lenses with small parallel striations engraved on them to assess fusion.
- Perception of depth, known as stereopsis, is measured using tests that create relative retinal disparity, such as contour type tests like Titmus Fly and Wirt circles, and random-dot type tests like Randot, TNO, Frisby, and Lang tests.
- Stereopsis is the binocular perception of relative distances between objects resulting from horizontal retinal disparities between monocular images.
- Stereopsis can be tested using real depth objects, polarising filters, anaglyphs, or random-dot patterns, with varying levels of difficulty.
- The TNO test uses red/green anaglyphic plates to measure stereoacuity, with the latest version having the lowest stereoacuity to 30”, which may be challenging for young children.
- The Frisby test involves real depth elements painted on one surface in squares, with different thickness plates creating different disparities for testing stereopsis.
- The Lang test uses small cylindrical lenses to separate the images to each eye, and it only measures gross levels of stereopsis.
- Questions can be asked via Brightspace discussion board or the chat function on Teams for further clarification on the testing methods.
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Description
Test your knowledge of visual direction and correspondence in binocular vision with this quiz. Explore concepts such as retinal local sign, oculocentric and egocentric direction, Hering's Law, cyclopean eye, horopter, and more. Sharpen your understanding of how the brain integrates visual information from both eyes to perceive depth and spatial relationships.
