Eye Muscle Function Quiz

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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?

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?

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?

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?

It will receive excessive neural signals causing it to overshoot the fixation target. Signup and view all the answers

What occurs during secondary deviation in eye muscle assessment?

The deviation is greater as it highlights the compensatory actions. Signup and view all the answers

What does a ‘+’ sign indicate when recording muscle actions?

An overaction of a muscle Signup and view all the answers

Which grading would indicate a muscle that does not move from its primary position?

Grade 4 Signup and view all the answers

What should be recorded if there is no incomitancy and the pursuit movements are smooth?

Full, smooth Signup and view all the answers

What does a ‘-’ sign represent when assessing muscle function?

An underaction of a muscle Signup and view all the answers

How much distance does a grade 3 underaction move from the primary position?

¼ of the distance Signup and view all the answers

What characterizes incommitant deviation in comparison to comitant deviation?

The angle of deviation changes depending on the direction of gaze. Signup and view all the answers

Which of the following best describes a neurogenic palsy?

A problem with the nerve supplying the muscle leading to reduced innovation. Signup and view all the answers

What is the difference between primary and secondary deviation in the context of neurogenic paresis?

Primary deviation is observed when the unaffected eye is fixating, whereas secondary occurs with the affected eye. Signup and view all the answers

Which type of incommitant deviation is caused by a physical restriction of eye movement?

Mechanical Signup and view all the answers

Herring’s and Sherrington’s laws relate to which aspect of ocular movement?

The relationship between muscle innervation in both eyes during fixation. Signup and view all the answers

In the context of eye muscle innervation, what does a reduction in nerve innovation lead to?

Underactivity of the affected muscle. Signup and view all the answers

Which of the following is NOT a characteristic of a comitant deviation?

Angle variation depends on fixation eye. Signup and view all the answers

When testing for incommitant deviations, what is the purpose of the six cardinal positions?

To determine the angle of deviation in various gaze positions. Signup and view all the answers

Which condition is typically linked to myogenic incommitant deviations?

Alterations in muscle elasticity or strength. Signup and view all the answers

What happens to the innervation in both eyes when one eye is fixating and affected by neurogenic paresis?

Innervation in the affected eye decreases while the other remains equal. Signup and view all the answers

What indicates that a muscle in the non-fixating eye is underacting?

The eye appears to lag behind when following a target Signup and view all the answers

In the context of eye muscle actions, which of the following responses is indicative of an overacting muscle?

Seeing two images where the left image is closer Signup and view all the answers

How can the alternating cover test help determine whether an eye muscle is underacting?

The underacting eye will move towards the target after covering the other eye Signup and view all the answers

Which of the following is a symptom of diplopia in relation to underacting muscles?

Experiencing double vision with one image appearing nearer Signup and view all the answers

When using the alternating cover test, what does it signify if the covered eye appears to overshoot the target?

The eye is exhibiting overaction due to muscle excess Signup and view all the answers

What role does the patient’s subjective response play in identifying muscle actions?

Patients can indicate the furthest light they see for underacting muscles Signup and view all the answers

Which statement correctly describes the lateral rectus muscle’s role in eye movement?

It primarily moves the eye away from the midline. Signup and view all the answers

If a patient reports seeing two targets during a movement test, what can typically be inferred?

One eye may be overacting and sees a closer image. Signup and view all the answers

How can the responses during an ocular motility examination help differentiate eye muscle actions?

Clear patterns emerge that indicate overaction or underaction Signup and view all the answers

What conclusion can be drawn from the observation that the left medial rectus is underacting?

The left eye will lag behind when tracking a target. Signup and view all the answers

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.

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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Description

Test your knowledge on eye muscle actions and assessments. This quiz covers important concepts such as signal strength to the lateral rectus and corneal reflection positioning during eye movements. Understand deviations and muscle behavior related to fixation.