Podcast
Questions and Answers
What does a strong signal to the lateral rectus of the fixating eye indicate about the corresponding muscle in the non-fixating eye?
What does a strong signal to the lateral rectus of the fixating eye indicate about the corresponding muscle in the non-fixating eye?
- It is overacting and will overshoot the fixation target. (correct)
- It maintains a normal response and follows the fixation target accurately.
- It will stop functioning temporarily until the signal decreases.
- It is underacting and will lag behind the fixation target.
In assessing muscle actions, which method primarily involves observing the positioning of the corneal reflections during eye movement?
In assessing muscle actions, which method primarily involves observing the positioning of the corneal reflections during eye movement?
- Alternating cover test
- Subjective patient questioning
- Observation of corneal reflections (correct)
- Assessment of muscle tone
When the medial rectus of the left eye is underacting, how will the corneal reflection appear in relation to the fixation target?
When the medial rectus of the left eye is underacting, how will the corneal reflection appear in relation to the fixation target?
- Fluctuating randomly in position relative to the fixation target.
- Closer to the fixation target than the pupil center. (correct)
- Further from the fixation target than the pupil center.
- Equal distance from the fixation target as the pupil center.
Which of the following best describes the behavior of the overacting muscle during fixation?
Which of the following best describes the behavior of the overacting muscle during fixation?
What occurs during secondary deviation in eye muscle assessment?
What occurs during secondary deviation in eye muscle assessment?
What does a ‘+’ sign indicate when recording muscle actions?
What does a ‘+’ sign indicate when recording muscle actions?
Which grading would indicate a muscle that does not move from its primary position?
Which grading would indicate a muscle that does not move from its primary position?
What should be recorded if there is no incomitancy and the pursuit movements are smooth?
What should be recorded if there is no incomitancy and the pursuit movements are smooth?
What does a ‘-’ sign represent when assessing muscle function?
What does a ‘-’ sign represent when assessing muscle function?
How much distance does a grade 3 underaction move from the primary position?
How much distance does a grade 3 underaction move from the primary position?
What characterizes incommitant deviation in comparison to comitant deviation?
What characterizes incommitant deviation in comparison to comitant deviation?
Which of the following best describes a neurogenic palsy?
Which of the following best describes a neurogenic palsy?
What is the difference between primary and secondary deviation in the context of neurogenic paresis?
What is the difference between primary and secondary deviation in the context of neurogenic paresis?
Which type of incommitant deviation is caused by a physical restriction of eye movement?
Which type of incommitant deviation is caused by a physical restriction of eye movement?
Herring’s and Sherrington’s laws relate to which aspect of ocular movement?
Herring’s and Sherrington’s laws relate to which aspect of ocular movement?
In the context of eye muscle innervation, what does a reduction in nerve innovation lead to?
In the context of eye muscle innervation, what does a reduction in nerve innovation lead to?
Which of the following is NOT a characteristic of a comitant deviation?
Which of the following is NOT a characteristic of a comitant deviation?
When testing for incommitant deviations, what is the purpose of the six cardinal positions?
When testing for incommitant deviations, what is the purpose of the six cardinal positions?
Which condition is typically linked to myogenic incommitant deviations?
Which condition is typically linked to myogenic incommitant deviations?
What happens to the innervation in both eyes when one eye is fixating and affected by neurogenic paresis?
What happens to the innervation in both eyes when one eye is fixating and affected by neurogenic paresis?
What indicates that a muscle in the non-fixating eye is underacting?
What indicates that a muscle in the non-fixating eye is underacting?
In the context of eye muscle actions, which of the following responses is indicative of an overacting muscle?
In the context of eye muscle actions, which of the following responses is indicative of an overacting muscle?
How can the alternating cover test help determine whether an eye muscle is underacting?
How can the alternating cover test help determine whether an eye muscle is underacting?
Which of the following is a symptom of diplopia in relation to underacting muscles?
Which of the following is a symptom of diplopia in relation to underacting muscles?
When using the alternating cover test, what does it signify if the covered eye appears to overshoot the target?
When using the alternating cover test, what does it signify if the covered eye appears to overshoot the target?
What role does the patient’s subjective response play in identifying muscle actions?
What role does the patient’s subjective response play in identifying muscle actions?
Which statement correctly describes the lateral rectus muscle’s role in eye movement?
Which statement correctly describes the lateral rectus muscle’s role in eye movement?
If a patient reports seeing two targets during a movement test, what can typically be inferred?
If a patient reports seeing two targets during a movement test, what can typically be inferred?
How can the responses during an ocular motility examination help differentiate eye muscle actions?
How can the responses during an ocular motility examination help differentiate eye muscle actions?
What conclusion can be drawn from the observation that the left medial rectus is underacting?
What conclusion can be drawn from the observation that the left medial rectus is underacting?
Flashcards
Incommitant deviation
Incommitant deviation
An eye movement disorder where the angle of deviation changes depending on the direction of gaze.
Comitant deviation
Comitant deviation
An eye movement disorder where the angle of deviation remains the same in all positions of gaze.
Mechanical restriction
Mechanical restriction
A deviation where the eye is restricted by a physical abnormality, such as a scar or tumor.
Neurogenic palsy
Neurogenic palsy
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Myogenic deviation
Myogenic deviation
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Primary deviation
Primary deviation
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Secondary deviation
Secondary deviation
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Six cardinal positions
Six cardinal positions
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Herring's law
Herring's law
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Sherrington's law
Sherrington's law
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Non-fixating eye
Non-fixating eye
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Fixating eye
Fixating eye
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Underaction
Underaction
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Overaction
Overaction
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Incommitant deviation diagram
Incommitant deviation diagram
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Overacting muscle
Overacting muscle
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Study Notes
Binocular Vision Lecture 10
- The lecture introduces incomitant deviations in binocular vision.
- Students will be able to describe what an incomitant deviation is.
- Students will be able to differentiate a comitant and incomitant deviation.
- Students will be able to differentiate between a paralytic and mechanical restriction.
Comitant Deviations
- Angle of deviation remains the same in all gaze positions.
- Example: Comitant exotropia.
- Herring's and Sherrington's law are relevant.
Incomitant Deviations
- The angle of deviation varies in different gaze directions.
- The angle of deviation varies depending on the eye used for fixation.
Testing for Incomitant Deviations
- The six cardinal positions are used.
- Testing in the vertical midline is sometimes required for assessing A and V patterns (later).
Classification of Incomitant Deviations
- Neurogenic (palsy): Problem with muscle innervation (reduced nerve signal).
- Myogenic: Problem with the muscle itself.
- Mechanical: Physical restriction of movement (eye not free to move).
Neurogenic Palsy
- A nerve supplying the muscle has a problem.
- Muscle is underacting due to reduced nerve signal.
- Example: Right lateral rectus palsy results in less innervation to the muscle causing it to underact.
Primary and Secondary Deviations
- Primary deviation: The fixating eye does not have neurological issue
- Secondary deviation: The fixating eye has the neurological issue.
- The size of the deviation depends on which eye is fixating and the location of any underaction/overaction.
Determining Over- and Under-Actions
- Motility: Observing corneal reflections.
- Subjective: Asking the patient (e.g., diplopia).
- Alternating cover test: Covering each eye to observe the reaction of the other.
The Underacting Muscle (Alternating Cover Test)
- The non-fixating eye is behind the relevant position.
- The patient reports seeing two targets (diplopia).
- The furthest target is the underacting eye.
The Overacting Muscle (Alternating Cover Test)
- The non-fixating muscle overshoots the fixation target.
- The patient reports seeing two targets (diplopia).
- The closest target is the overacting eye
Recording Results--Advanced
- Grading over- or under-actions on a scale of 1 to 4.
- 4: no movement.
- 3: 1 ½ the distance from the primary position.
- 2: 1 ½ the distance from the primary position.
- 1: ¼ the distance from the primary position.
Further Reading
- Evans, BJW. (2007) Pickwell's binocular vision anomalies: Investigation and treatment. 5th edn, Philadelphia: Butterworth-Heinemann.
Formative Exam Details
- The formative exam is on Monday, December 11th.
- Arrive on time.
- Bring a pencil.
- Bring a calculator.
- Bring the tamperproof sticker. (No calculators on the exam day).
Passive Exam Details
- The passive exam includes a multiple choice section (40 marks).
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