Binocular Vision and Visual Processing Quiz

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Questions and Answers

What term describes the visual direction that is associated with each point on the retina and its corresponding nodal point?

Binocular reference point

Principal visual direction (correct)

Egocentric direction

Secondary visual direction

What distinguishes binocular vision from monocular vision?

It relies on a single oculocentric frame of reference.

It requires only one eye to observe visual direction.

It eliminates the use of the nodal point in visual processing.

It integrates the inputs of two eyes to create depth perception. (correct)

How does light passing through the nodal point affects visual perception?

It is necessary for determining both principal and secondary visual direction. (correct)

It impacts the perception of color in the visual spectrum.

It exclusively creates perception for monocular vision.

It only defines the secondary visual direction.

In the context of binocular vision, what does the term 'oculocentric' refer to?

The independent reference frame of each eye in visual perception. Signup and view all the answers

What is the primary function of the nodal point in visual processing?

To serve as a common point for light paths from both eyes. Signup and view all the answers

What occurs during the critical period regarding strabismus?

Visual development is dependent on sufficient sensory stimulation. Signup and view all the answers

In the context of suppression, what does the brain do to manage diplopia?

It ignores the image from the non-dominant eye in binocular vision. Signup and view all the answers

What is a consequence of full suppression during binocular vision?

It results in reduced depth perception. Signup and view all the answers

Which option describes a possible intervention for treating intractable diplopia?

An occlusive contact lens can be used for direct eye treatment. Signup and view all the answers

What is a common result of amblyopia associated with strabismus in children?

Reduced vision in the suppressed eye. Signup and view all the answers

What visual perception would a patient with a right exotropia experience when using the Maddox rod?

They would only see a spot of light. Signup and view all the answers

What outcome occurs when assessing phorias using a Maddox rod in a patient who is not binocular?

It will not provide any meaningful results regarding phorias. Signup and view all the answers

In the context of visuospatial processing, what might a patient with right exotropia experience while using the Mallet unit?

They would see two separate mallet units distinctly. Signup and view all the answers

What visual outcome is expected when a patient suppresses the visual field of the right eye during the Mallet unit testing?

They will see only the upper strip of the nonius target. Signup and view all the answers

When conducting a routine assessment of vision, which of the following would suggest the patient is not binocular?

Difficulty with subjective phoria assessment methods. Signup and view all the answers

What condition results in the perception of two images due to the alignment of retinal images on non-corresponding points?

Diplopia Signup and view all the answers

Which type of diplopia occurs when the image falls on the fovea of one eye and on the nasal retina of the other?

Uncrossed diplopia Signup and view all the answers

In the case of an individual with strabismus, which of the following is NOT a possible outcome?

Loss of monocular vision Signup and view all the answers

What is the main clinical approach for treating diplopia?

Prisms Signup and view all the answers

What visual arrangement occurs in a hypertropic eye?

Hypertropic eye sees the image above Signup and view all the answers

What is a potential distressful symptom experienced by patients with strabismus?

Diplopia Signup and view all the answers

Which factor may allow a patient to adapt to diplopia?

Compensatory head posture Signup and view all the answers

In the description of esotropia, where does the image fall on the right eye?

On the nasal retina Signup and view all the answers

What does the cyclopean eye represent in the context of binocular vision?

The combined visual direction from both eyes Signup and view all the answers

What is the significance of the horopter in visual perception?

It indicates points with the same visual direction for both eyes Signup and view all the answers

What is the shape of the horopter as proposed by Veith and Muller known as?

Veith-Muller circle Signup and view all the answers

What condition is associated with images that do not fall on the horopter?

Physiological diplopia Signup and view all the answers

What occurs within Panum's fusional area?

Single vision is maintained despite some retinal disparity Signup and view all the answers

How is crossed diplopia characterized in terms of visual perception?

Images fall on opposing sides of the horopter Signup and view all the answers

What defines uncrossed diplopia in visual terms?

Images fall behind the horopter and appear similarly Signup and view all the answers

What happens to the image from the left eye in right exotropia?

It lands on the fovea of the left eye Signup and view all the answers

What is the primary function of corresponding points in binocular vision?

To unify images from both eyes into a single perception Signup and view all the answers

What visual phenomenon occurs when an object is perceived outside of Panum’s fusional area?

Physiological diplopia Signup and view all the answers

What indicates normal binocular vision during the Worth 4-Dot Test?

The patient sees four dots. Signup and view all the answers

What does the presence of two dots in the Worth 4-Dot Test indicate?

Suppression in the left eye. Signup and view all the answers

How does the depth of suppression get assessed using a Neutral Density filter?

By introducing a red filter over the good eye. Signup and view all the answers

In a patient with total suppression, what would be expected regarding their stereopsis?

The patient will have no stereopsis. Signup and view all the answers

Which stereotest uses polarised glasses to assess stereopsis?

Titmus Stereotest. Signup and view all the answers

What condition does the Mallet suppression test primarily evaluate?

Area of suppression. Signup and view all the answers

Which statement best describes the significance of seeing three dots in the Worth 4-Dot Test?

Indicates suppression of the right eye. Signup and view all the answers

What role do the central targets and peripheral surround play during testing?

They serve as fusion locks. Signup and view all the answers

In the context of suppression recording, what does the term 'intermittent' signify?

The suppression occurs sporadically. Signup and view all the answers

What visual acuity measures does the Frisby Stereotest rely upon?

Thickness of the plates and test distance. Signup and view all the answers

When is the only time suppression may be recorded at a distance but not at near?

When using the Worth 4-Dot Test. Signup and view all the answers

During the Mallet suppression test, what visual component serves as a 'foveal lock'?

Central 'O's visible to both eyes. Signup and view all the answers

What does the TNO stereotest utilize to assess stereopsis?

Random dot patterns. Signup and view all the answers

Study Notes

Binocular Vision Lecture Notes

Lecture Recording: The lecture is being recorded and will be available via Panopto on the module DLE pages shortly.
Feedback: Students can provide feedback through the "Your Voice" system at yourvoice.telmed.uk.
Nut-Free Zone: The PAHC building is a nut-free zone. Students and staff with allergies should be mindful about bringing food and drinks.
Asking Questions During Recording: Students can ask questions during the lecture. Pause requests may be possible if a student doesn't wish their question to appear on the recording.

Development of Normal Binocular Vision

Oculocentric Monocular Vision: Each point on the retina has its own visual direction, passing through the eye's nodal point.
Principal Visual Direction: The principal visual direction is along the visual axis, where light passes through the nodal point to reach the fovea.
Secondary Visual Direction: The secondary visual direction refers to the light passing through the nodal point to reach other points on the retina.

Visual Direction—Binocular Monocularly

Egocentric Binocular Vision: Each eye has its own oculocentric frame of reference. Visual perception is imagined to originate from an imaginary cyclopean eye between the two real eyes.
Two Foveae (f₁ and fR): These have identical visual directions, focusing on F—represented as a single cyclopean fovea (fc).

Finding the Cyclopean Eye

Method: With both eyes open, point at a spot. Close the right eye, then close the left eye. The alignment of the fingers with the target suggests the dominant eye. If both are equally aligned, you have a true cyclopean eye—meaning both eyes give the same reading distance.

The Horopter

Definition: For each focal point, all corresponding points are located on the horopter.
Example: Point O lies on the horopter of point F.

Vieth-Muller Circle

Definition (1818): Veith and Muller defined the circular shape of the horopter. It passes through the nodal points of each eye and the fixation point.
Reality: The horopter is likely elliptical, not perfectly circular.

Corresponding Points

Definition: Objects falling on the horopter have the same visual direction in both eyes, therefore at a corresponding point.
Single Object Perception: These points are perceived as a single object.

Disparate Points

Definition: Objects not falling on the horopter have different visual directions in each eye and are called disparate points.
Double Vision (Diplopia): These points are seen as double. This is called physiological diplopia.

Panum's Fusial Area

Tolerance: Each point on one retina corresponds to a larger area on the other eye.
Single Vision: Single vision still occurs, as long as an object falls within Panum's area.
Diplopia: Physiologic diplopia only occurs outside of this area.

Crossed Diplopia

Location: The object lies in front of the horopter.
Perception: The image from the right eye appears on the left side of fixation, and the image from the left eye on the right side of fixation.

Uncrossed Diplopia

Location: The object lies behind the horopter.
Perception: The right eye's image appears on the right side of fixation; the left eye's image on the left side of fixation.

Binocular Single Vision and Strabismus

Adaption: Vision adaptation varies by the degree of strabismus. Students may experience diplopia/confusion, suppression, or abnormal retinal correspondence.

Right Exotropia

Fixation: The left eye is fixated on the target.
Strabismus: The right eye is exotropic—deviates outward from the target.
Perception: The image falls on the fovea of the left eye, and the right eye's image is on the temporal retina, leading to the perception of the image on the left side of the right eye.

Sensory Adaption

Three Possible Outcomes: Diplopia and confusion; suppression; abnormal retinal correspondence.

Diplopia and Confusion

Image Fall: The retinal image of an object is on the fovea of one eye but on the peripheral retina of the other eye.
Perception: Two images are perceived.
Distress: Can be very distressing for patients.

Diplopia and Confusion (Confusion)

Fovea Comparison: Different retinal images fall onto both foveas.
Different Space Perception: These corresponding points fall into the same visual space, creating a conflict.
Brain's Inability to Fuse: The brain cannot combine these distinct images.
Distress: Also very distressing.

Exotropia

Image Fall: Image falls on the fovea of the left eye. Temporal retina of right eye.
Perception: The right eye sees the image on the left.
Diplopia: This leads to crossed diplopia.

Esotropia

Image Fall: Image falls on the fovea of the left eye; nasal retina of the right eye.
Perception: The right eye sees the image on the right.
Diplopia: This leads to uncrossed diplopia.

Hypertropia

Image Fall: Image falls on the superior retina of the hypertropia eye.
Perception: The eye sees the image below the fixating eye.

Hypotropia

Image Fall: Image falls on the inferior retina of the hypotropia eye.
Perception: The eye sees the image above the fixating eye.

What Can Be Done About Diplopia

Adaptation: Some patients adapt by adjusting their head and neck posture.
Prisms: Prisms can help, but aren't always effective.
Surgery: Surgery may be necessary, but isn't necessarily helpful for restoring binocular vision. It is primarily for cosmetic benefit.
Occlusion: If the issue is intractable, occlusion methods might be employed.

Occlusion Methods

Occlusive Contact Lenses: A way to cover the eye to treat diplopia.
Eyelid Occlusion: Covering the eye, often using an eye-patch or spectacle lens.
Eye Patch: Used to cover strabismic eye.
Botulinum Toxin: Administered to temporarily relax eye muscles.

Suppression

Definition: Suppression occurs during binocular viewing when one eye does not get processed.
Mechanism: The brain is suppressing the image from one eye to avoid the diplopia it causes.

Suppression of Binocular Visual Field

Diplopia Correction: To avoid seeing double images, the brain suppresses images from one eye.
Critical Period: This adaption occurs if the strabismus was present in childhood.

Critical Period

Duration: Vision adaption occurs from birth to approximately age 8-10 years, a time critical for strabismus development.
Neural Connections: Neural connections aren't fully formed or developed.
Adaption Likelihood: Adaption is more probable within the critical period.
Treatment Effectiveness: Treatment is more likely to be effective.

Full Suppression

Binocular Vision: The brain ignores the non-fixating eye's image in binocular conditions.
Depth Perception: This reduced depth perception is not ideal.

Suppression and Amblyopia

Critical Period & Development: Proper sensory stimulation during the critical period is essential for proper visual development—including the function of both eyes.
Suppression effect: During the critical period, suppression of one eye can lead to a reduction in visual function in that eye.
Amblyopia Definition: Amblyopia is reduced vision owing to strabismus (misalignment of the eyes) that typically happens within the critical period of visual development.

Tests to Investigate Suppression

Worth 4-Dot Test: Tests for binocular single vision, diplopia, or suppression using red and green glasses and dots.
Stereopsis Tests: Tests for binocular vision or stereopsis.
Mallet Unit: Used to observe fusion lock under various conditions.
Bagolini Lenses: Assess stereopsis.
Neutral Density Filters: Tests for the depth of suppression.

What to Know About Suppression

Eye Identification: Which eye is affected?
Area of Suppression: Where is the area of suppression?
Pattern of Suppression: Is it constant or intermittent?

Assessment of Vision Considerations (Routine Assessment)

Binocular Balancing: If suppression occurs, binocular balancing won't function as it should.
Stereopsis absence: Stereopsis is not present due to the suppression and imbalance.
Phoria Assessment: Subjective methods, like the Maddox rod, mallet unit, and Maddox wing, will not provide accurate phoria assessments if suppression is present.

Maddox Rod Testing

Right Exotropia: In the case of right exotropia, the right eye will see the red line, while the left eye sees the spot of light.

Maddox Rod Suppression

Suppression: The right eye, despite strabismus, will suppress the red line, only the left eye sees the spot of light on the rod.

Mallet Unit Testing

Right Exotropia: If the patient had right exotropia and suppresses the right eye's visual field, the patient will see the two halves of the unit independently, one in each eye.

Mallet Unit Suppression Testing

Suppression Impact: The right eye might suppress the information from the right side of the target if they have a right exotropia, causing the patient to see only the left on the Mallet unit.

Tests to Investigate Suppression (Specific Tests)

Worth 4 dots: These are tests to investigate suppression using red/green glasses and target dots.
Stereopsis Tests: These are tests to investigate how the eyes work together.
Bagolini Lenses: These are corrective lenses, assessing depth perception in binocular vision.
Neutral Density Filters: These filters are used to examine the intensity of an image, helping determine the depth of suppression.

Worth 4-Dot Test Considerations

Setup: Red goggles over the right eye and green over the left eye.
Test Distance: Testing is carried out at near (40cm) or more distant (6m) and under various lighting conditions.
Patient Setup: The patient's gaze should be level; the light must be above the test target to see it without turning the head.

Worth 4-Dot Test Procedure

Dots Visible: The displayed dots are used to check for binocular single vision in either one or both eyes.
Number of Dots: The patient's visible dots will show the situation. Examples include:
Four dots—normal binocular vision.
Two dots—suppression of one eye.
Three dots—suppression of the other eye.
Five dots—the patient is seeing two sets of dots.

Suppression Depth

Neutral Density Filters: To determine the depth of suppression, a neutral density filter is used to dim the light in the patient's good eye until the patient perceives only one dot in the good eye.
Filter Application: A red filter is used near the good eye first. The visual experience with this will gradually change as the patient sees one spot, then a pink spot, then a white spot, when the intensity changes on the light source.

Stereoscopic Tests

Total Suppression: No stereoscopic function will be detected if suppression is present.
Partial Stereoscopic Function: If stereoscopic function is present, there is likely some degree of binocular vision.

Lang Stereotest

Target: The target includes images of an elephant, a truck, or the moon, which are presented to the patient.
Target Characteristics: These images have differing disparity values.

Frisby Stereotest

Plates: These have graduated levels of disparity. The larger the distance, the more thickness and depth.
Usefulness: The test is used to assess binocular vision and estimate the level of depth perception.

Titmus Stereotest

Glasses: This is a test that assesses stereoscopic function and uses polarized lenses.
Target: This test uses images projected on two screens or circles, designed to help calculate various degrees of disparity.
Visual Cues: The test uses visual cues involving contour targets, creating a localised visual experience.

TNO Stereotest

Pattern: Uses a random dot pattern.
Goggles: Red and green glasses are necessary.
Measurement: Measures disparity down to 15 seconds of arc.

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Description

Test your knowledge on key concepts of binocular vision and visual processing. This quiz covers terms and functions associated with the retina, nodal point, and effects of strabismus. Assess your understanding of how the brain manages visual perception and diplopia.