Binocular Vision Lecture 2 - Extraocular Movements

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary purpose of the optokinetic reflex?

To maintain an image on the retina at low visual stimulus velocities (correct)

To generate rapid eye movements in response to high visual frequencies

To facilitate accommodation in the presence of rapid motion

To stabilize the image during head movement at all visual stimulus velocities

What does 'incomitance' imply during ocular motility assessment?

The visual axes maintain a consistent angle regardless of gaze direction

The patient’s eyes are unable to perform version movements

The angle between visual axes varies with changes in direction of gaze (correct)

The presence of double vision in all positions of gaze

During the motility test, what is the recommended setup for the room and equipment?

Room lights should be set to low; target should be a stationary object

Room lights on; use a visible pen torch as the target (correct)

Room lights should be turned bright; patient should not be informed of the test procedure

Room lights off; glasses should be worn during the test

What should the examiner observe when moving the pen light during the motility test?

For any misalignments of the corneal reflex in the gaze positions Signup and view all the answers

Which statement best describes the role of the extraocular eye muscles during ocular motility assessment?

They allow assessment of the patient's ability to maintain binocular vision Signup and view all the answers

What characterizes the position of anatomical rest?

Eyes reflect an angle between orbital axes of about 45° without muscle innervation. Signup and view all the answers

Which of the following best describes fusional convergence?

The adjustment of the eyes to fuse on a target due to retinal disparity. Signup and view all the answers

What differentiates heterophoria from orthophoria?

Existence of a difference between associated and dissociated positions. Signup and view all the answers

What is a key characteristic of saccade movements?

They are rapid, short, and abrupt movements. Signup and view all the answers

How does the vestibulo-ocular reflex function?

It stabilizes the image on the retina during head movement. Signup and view all the answers

Which movement category involves maintaining fixation on a moving object?

Smooth pursuit movements Signup and view all the answers

What physiological function is avoided by fixational eye movements?

Stabilized retinal image Signup and view all the answers

During the cover test, what type of position is observed when one eye is covered?

Dissociated (Passive) position Signup and view all the answers

What is the physiological response during a saccade?

Vision is suppressed to allow the movement. Signup and view all the answers

What defines smooth pursuit movements in terms of speed?

They are incapable of maintaining fixation when speed exceeds approximately 40 degrees per second. Signup and view all the answers

What muscle is primarily responsible for abduction of the eye?

Lateral Rectus Signup and view all the answers

During adduction, which muscle contracts?

Medial Rectus Signup and view all the answers

What is the primary action of the superior rectus during abduction and elevation?

Elevation Signup and view all the answers

If a patient exhibits discomfort in eye movement tests, what should be recorded?

Any discomfort experienced Signup and view all the answers

Which muscle acts as the antagonist during infraduction?

Superior Rectus Signup and view all the answers

What defines mechanical incomitancy during monocular motility tests?

Similar underaction in both version and duction Signup and view all the answers

Which muscle contracts during adduction and elevation?

Superior Rectus Signup and view all the answers

In which movement does the inferior rectus contract?

Abduction and depression Signup and view all the answers

What is tested by observing actions of yoke muscles?

Integrity of synergists Signup and view all the answers

What occurs if no abnormality is detected during the examination of eye movements?

Label findings as 'full smooth' Signup and view all the answers

What is the primary action of the lateral rectus?

Abducting the eye Signup and view all the answers

During which eye movement does the superior oblique relax?

Adduction and elevation Signup and view all the answers

What does a smooth pursuit indicate during eye movement testing?

Proper muscle contraction during movements Signup and view all the answers

What aspect is crucial when diagnosing underaction or overaction in eye movement?

Testing ductions after initial exams Signup and view all the answers

Study Notes

Binocular Vision Lecture 2 - Normal Extraocular Movement Part 2

The lecture is being recorded and will be accessible via Panopto.
Recorded comments and questions may be included in the recording.
Students can request pauses if they don't want their questions or comments recorded.
Learning objectives for the session:
- Identify positions of rest and fixation.
- Explain the difference between saccadic and pursuit movements and how each is tested.
- Understand how to perform extraocular movement examinations.
- Recognize the muscles and types of movements assessed during ocular motility testing.

Positions of Rest and Fixation

Anatomical rest:
- Eye position without muscle tone or postural reflexes.
- Typically occurs in death.
- Represents roughly 45° angle between orbital axes.
- Eyes are generally divergent due to orbital anatomy.
Physiological rest:
- Eye position in the absence of a fixational reflex.
- Determined by postural reflexes and muscle tone.
- Occurs in total darkness.

Effect of Accommodation

Accommodation and convergence are related.
As accommodation increases, convergence also increases.

Fusional Convergence

Fine-tuning eye movement to fuse a target.
Retinal images are focused onto corresponding points.

Dissociated (Passive) Position

Position when fusional convergence is absent, but other factors are present.
Occurs when one eye is covered (cover test).
Present in other tests preventing eye fusion (Maddox rod and Maddox wing).

Associated (Active) Position

Eyes positioned with fusional convergence along with other physiological factors.
Retinal disparity triggers fusional vergence, positioning the eyes.

What This Means

Deviation of eye position (heterophoria) exists if associated and dissociated positions are different.
If no difference, then it is orthophoria.

Categories of Version Movements

Saccades
Smooth Pursuit Movements
Fixational Eye Movements
Vestibulo-Ocular Reflex
Optokinetic Nystagmus

Saccades

Short, rapid, and abrupt movements.
Occur during reading and fixating between points.
Rods and cones respond to luminance changes.
Peak velocity of a 10° saccade is often over 300°/second.
Vision is suppressed during a saccade.

Smooth Pursuit Movements

Eye movement while fixating a moving target.
Smooth eye movement as long as the object's speed is below approximately 40 degrees per second.

Fixation Eye Movements

Maintaining an image's center within the fovea.
Quick eye movements (physiological nystagmus).
Varying amplitude and frequency.
Prevents retinal image stabilization fatigue, ensuring image clarity.

Vestibulo-Ocular Reflex

Eyes move opposite to the head's movement.
Triggered by semicircular canal stimulation.
Maintains image clarity on the retina during head movement.
Best responsive with high visual stimulus velocities and frequencies (e.g., spinning).
Also involves at lower stimulus rates/frequencies (optokinetic reflex).

Optokinetic Nystagmus (OKN)

Physiological eye movement.
Called "train nystagmus."
Occurs when watching objects moving across the visual field.

Ocular Motility

Assesses a patient's ability to look in all directions, including version movements.
Evaluates extraocular muscles.
Determines if eye deviations (comitance/incomitance).
Comitance - direction unchanging
Incomitance - angle of deviation changes in different gazes.

Motility Test - Setup

Routine test.
Adjust room light to see corneal reflections.
No glasses.
Use a pen torch as a target.
Direct positioning ensuring both eyes are visible to the examiner.
Explain the test to the patient with instruction to follow the light and keep the head still. Indicate to tell the examiner if any double vision is present.

Motility Test - Procedure

Hold the pen light 40 cm from the patient.
Move the light in radial directions across all six cardinal positions of gaze.
Keep the light within the binocular field of vision.
Aim for 20-25 degrees from the primary position.
Observe for corneal reflex misalignments.
Check for points where the patient experiences double vision.
Check for 'A' and 'V' patterns (to be further explained later).

The Six Cardinal Positions

Assess integrity of synergist (yoke) muscles.
Includes specific eye movements (e.g., RSR, RIO, LIO, LSR, RLR, LMR, RMR, LLR, RIR, LSO, RSO, LIR).
Testing in the vertical midline is only required to assess 'A' and 'V' patterns.

Muscles Involved with Ductions

Table detailing agonist and antagonist muscles for different eye movements.

Specific Eye Movements (E.g., Abduction, Adduction, Abduction and Elevation, Abduction and Depression, Adduction and Elevation)

Specific muscles involved in these movements are examined based on the greatest exertion of action for each movement along with corresponding relaxed muscles for each movement.

Recording Findings

Record findings if no abnormalities noted - full smooth eye movements.
In cases of abnormalities, record if any discomfort, jerky, or inaccurate pursuit eye movements occur.
Note underaction and overaction detection, and if necessary, conduct further duction testing.

Monocular Motility Test (Testing for Ductions)

Repeat motility test using one eye at a time.
Determines if restriction is paretic or mechanical.
If underaction occurs less during version than duction, paresis is often the likely cause.
If similar underaction occurs for both version and duction movements, mechanical restriction is more likely.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the concepts of positions of rest and fixation in binocular vision in this second lecture. Learn about saccadic and pursuit movements, testing methods, and how to conduct extraocular movement examinations. This session will enhance your understanding of ocular motility testing and the muscles involved.