Extraocular Motility
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Questions and Answers

What is the function of a synergist muscle in extraocular motility?

  • Acts as an antagonist
  • Moves the eye in the opposite direction
  • Moves the eye in a random direction
  • Helps the agonist to produce a given movement (correct)

    • Herings' Law of Equal Innervation states that the innervation flow to the agonist and antagonist muscles is always unequal.

    False

    What is the role of yoke muscles in extraocular motility?

    To move the eyes in a desired gaze position

    During right up gaze, the yoke muscles involved are ___________________ and ___________________.

    <p>RSR and LIO</p> Signup and view all the answers

    What is the antagonist of RLR during right end gaze?

    <p>RMR</p> Signup and view all the answers

    What is the law that states that during eye movements, there is an increased flow of innervation to the contracting agonist muscle and a decreased flow of innervation to the relaxing antagonist muscle?

    <p>Sherrington's Law of Reciprocal Innervation</p> Signup and view all the answers

    The primary muscle moving the eye in a given direction is known as the ___________________.

    <p>agonist</p> Signup and view all the answers

    Match the following movements with their corresponding yoke muscles:

    <p>Right end gaze = RLR &amp; LMR Left up gaze = LSR &amp; RIO Right down gaze = RIR &amp; LSO Left end gaze = LLR &amp; RMR</p> Signup and view all the answers

    What is the purpose of the NSUCO grading scale in the testing procedure?

    <p>To rate the performance in 4 categories</p> Signup and view all the answers

    True or False: Stereoscopic vision requires a small binocular overlap of the visual field.

    <p>False</p> Signup and view all the answers

    What is the primary function of pursuit eye movements?

    <p>To track a moving object in the environment.</p> Signup and view all the answers

    Uncrossed disparity occurs when objects are _______________ the object of focus.

    <p>behind</p> Signup and view all the answers

    Match the following professions with their relevance to stereopsis:

    <p>Pilots = Requires stereoscopic vision for depth perception Policemen = Requires stereoscopic vision for depth perception Surgeons = Requires stereoscopic vision for depth perception Microbiologist = Does not require stereoscopic vision</p> Signup and view all the answers

    What is the name of the test used to evaluate saccadic eye movements?

    <p>NSUCO test</p> Signup and view all the answers

    True or False: The worth four dot test is used to evaluate stereopsis and fusion.

    <p>True</p> Signup and view all the answers

    What are the three main requirements for stereoscopic vision?

    <ol> <li>Large binocular overlap of the visual field, 2) Partial decussation of the afferent visual fibers, and 3) Coordinated conjugate eye movements.</li> </ol> Signup and view all the answers

    What is the muscle combination for right up gaze (Dextroelevation)?

    <p>RSR &amp; LIO</p> Signup and view all the answers

    The H Test is used to detect comitant deviation.

    <p>False</p> Signup and view all the answers

    What is the purpose of the Motility Test - Broad H Test?

    <p>To detect restriction of eye movements in different gaze positions and non-comitant deviation</p> Signup and view all the answers

    The ability to maintain a steady fixation on a fixation target is known as ________________.

    <p>fixation</p> Signup and view all the answers

    Match the following eye movements with their descriptions:

    <p>Fixation = Redirect the eyes fixation from one target to another Saccade = The ability to maintain a steady fixation on a fixation target Pursuit = Slow and smooth eye movement</p> Signup and view all the answers

    What is the muscle combination for left down gaze (Levodepression)?

    <p>LIR &amp; RSO</p> Signup and view all the answers

    During the H Test, the subject is instructed to move their head.

    <p>False</p> Signup and view all the answers

    What is the symptom of skipping words when reading?

    <p>Poor eye movement or saccadic dysfunction</p> Signup and view all the answers

    Which cranial nerve controls the Superior Oblique (SO) muscle?

    <p>CN IV</p> Signup and view all the answers

    Ductions are binocular eye movements.

    <p>False</p> Signup and view all the answers

    What is the primary position of gaze?

    <p>Straight-ahead position</p> Signup and view all the answers

    The _______________ type of eye movement is where both eyes move in opposite directions.

    <p>vergence</p> Signup and view all the answers

    Which type of version is when the gaze moves towards the right?

    <p>Dextroversion</p> Signup and view all the answers

    Match the following types of eye movements with their descriptions:

    <p>Ductions = Monocular eye movements Versions = Binocular eye movements Vergence = Eye movements in opposite direction</p> Signup and view all the answers

    Convergence is when both eyes move away from the midline.

    <p>False</p> Signup and view all the answers

    What is the purpose of testing ductions?

    <p>To test monocular eye movements</p> Signup and view all the answers

    What is the formula to calculate vergence demand?

    <p>IPD (in cm) x 100 / (d + 2.7)</p> Signup and view all the answers

    Tonic vergence can be measured directly.

    <p>False</p> Signup and view all the answers

    What is the normal range of AC/A ratio?

    <p>4 to 6:1</p> Signup and view all the answers

    The movement of both eyes in the same direction is known as ________ movements.

    <p>version or conjugate</p> Signup and view all the answers

    What is accommodative convergence?

    <p>Convergence of eyes due to accommodative effort</p> Signup and view all the answers

    Match the type of vergence with its description:

    <p>Tonic Vergence = Awareness of nearness/perception of distance Proximal Vergence = Tone of muscle; no adequate stimulus Accommodative Vergence = Retinal disparity Fusional Vergence = Accommodative Convergence – Far -&gt; Near</p> Signup and view all the answers

    Supra vergence is a type of convergent movement.

    <p>True</p> Signup and view all the answers

    What is the unit of measurement of vergence demand?

    <p>Prism diopters (∆)</p> Signup and view all the answers

    What is the purpose of the Fusional Vergence Amplitude test?

    <p>To assess the strength of fusional vergence reserves</p> Signup and view all the answers

    What type of prisms are not used in the Fusional Vergence Amplitude test?

    <p>Single prisms</p> Signup and view all the answers

    What is the purpose of the fixation target in the Fusional Vergence Amplitude test?

    <p>To provide a clear visual target for the patient</p> Signup and view all the answers

    What is the unit of measurement of the results of the Fusional Vergence Amplitude test?

    <p>Prism diopters</p> Signup and view all the answers

    What is the term for the point at which the patient's eyes can no longer fuse and single vision is broken?

    <p>Break point</p> Signup and view all the answers

    What is the primary position of gaze?

    <p>When the eye is looking straight ahead with the visual axis parallel to the sagittal plane of the head</p> Signup and view all the answers

    What is the difference between heterophoria and heterotropia?

    <p>Heterophoria is a latent deviation and heterotropia is a manifest deviation</p> Signup and view all the answers

    What is the term for the point at which the patient's eyes regain fusion after breaking?

    <p>Recovery point</p> Signup and view all the answers

    What is the purpose of measuring the NFV and PFV values in the Fusional Vergence Amplitude test?

    <p>To measure the patient's fusional vergence reserves</p> Signup and view all the answers

    What is orthophoria?

    <p>An ocular condition in which the two lines of sight meet at the object of regard, even when one eye is occluded</p> Signup and view all the answers

    What is the Cover Test used for?

    <p>To diagnose heterotropia</p> Signup and view all the answers

    What is the typical distance used for far fixation in the Fusional Vergence Amplitude test?

    <p>6 meters</p> Signup and view all the answers

    What is the main difference between monocular and binocular conditions?

    <p>Monocular conditions involve one eye, while binocular conditions involve both eyes</p> Signup and view all the answers

    What is the prevalence of exophoria?

    <p>1-3 prisms of exophoria</p> Signup and view all the answers

    What is the main characteristic of intermittent deviation?

    <p>Initially, the eye looks orthophoric and after cover test, it shows tropia</p> Signup and view all the answers

    What is the main difference between phoria and tropia?

    <p>Phoria is a latent deviation, while tropia is a manifest deviation</p> Signup and view all the answers

    What is the minimum FV reserve blur required for asymptomatic exophoria according to Sheard's criteria?

    <p>twice the phoria</p> Signup and view all the answers

    What is the purpose of prescribing prisms based on fixation disparity?

    <p>to treat fixation disparity</p> Signup and view all the answers

    What is the primary function of the NSUCO grading scale?

    <p>To rate the performance in 4 categories</p> Signup and view all the answers

    A patient has a NFV of 3 BI and a PFV of 15 BO. What is the prism required to decrease PFV to 12 pd and increase NFV to 6 pd?

    <p>3 BO</p> Signup and view all the answers

    Which criterion is a good discriminator for exo deviations?

    <p>Sheard's criterion</p> Signup and view all the answers

    A patient has a near phoria of 10 XP and a PFV blur of 20 pd. How many prisms of base-in prism are required?

    <p>2 prisms</p> Signup and view all the answers

    What is the midpoint of phoria position required for non-symptomatic esophoria according to Percival's criteria?

    <p>in the middle one third of FV with 2/3 PFV and 1/3 NFV</p> Signup and view all the answers

    What is the requirement for stereoscopic vision?

    <p>Large binocular overlap of the visual field</p> Signup and view all the answers

    What is the primary purpose of the Motility Test - Broad H Test?

    <p>To detect non-comitant deviation and restriction of eye movements in different gaze positions</p> Signup and view all the answers

    What is the type of disparity that occurs when objects are behind the object of focus?

    <p>Uncrossed disparity</p> Signup and view all the answers

    What is the muscle combination for right down gaze (Dextrodepression)?

    <p>RIR and LSO</p> Signup and view all the answers

    Which profession requires stereoscopic vision?

    <p>Surgeon</p> Signup and view all the answers

    What is the symptom of reading the same line or letters twice or skipping a line?

    <p>Fixation impairment</p> Signup and view all the answers

    What is the purpose of the Worth four dot test?

    <p>To evaluate stereopsis and fusion</p> Signup and view all the answers

    What is the type of eye movement that is conjugate?

    <p>Saccade</p> Signup and view all the answers

    What is the testing procedure for pursuits?

    <p>One target moving in a circle of 20cm diameter</p> Signup and view all the answers

    What is the law that states that during eye movements, there is an increased flow of innervation to the contracting agonist muscle and a decreased flow of innervation to the relaxing antagonist muscle?

    <p>Sherrington's Law of Reciprocal Innervation</p> Signup and view all the answers

    What is the primary function of fixation?

    <p>To maintain a steady fixation on a fixation target</p> Signup and view all the answers

    What is the rating scale used for saccades and pursuits?

    <p>NSUCO grading scale</p> Signup and view all the answers

    What is the purpose of testing saccadic eye movements?

    <p>To evaluate the ability to track a moving object in the environment</p> Signup and view all the answers

    What is the muscle combination for convergence?

    <p>LMR and RMR</p> Signup and view all the answers

    What is the purpose of the procedure in the Motility Test - Broad H Test?

    <p>To move the target in a H pattern</p> Signup and view all the answers

    What is the symptom of excessive head movement while reading?

    <p>Fixation impairment</p> Signup and view all the answers

    What is the type of eye movement that is where both eyes move in opposite directions?

    <p>Vergence</p> Signup and view all the answers

    Study Notes

    Extraocular Motility

    • Six muscles control extraocular movements: 4 recti and 2 obliques
    • Control by cranial nerves: Oculomotor (CN III), Trochlear (CN IV), and Abducens (CN VI)
    • Types of eye movements: Ductions, Versions, and Vergence

    Ductions

    • Monocular eye movements
    • Tested monocularly by covering one eye
    • Six types of ductions:
      • Horizontal direction: Abduction (eye moves away from midline) and Adduction (eye moves towards midline)
      • Vertical direction: Supraduction (eye moves upwards) and Infraduction (eye moves downwards)
      • Cycloversion: Incycloduction (rotation of upper cornea towards midline) and Excycloduction (rotation of upper cornea away from midline)

    Versions

    • Binocular eye movements
    • Tested binocularly by covering one eye
    • Six types of versions:
      • Horizontal direction: Dextroversion (gaze moves towards the right) and Levoversion (gaze moves towards the left)
      • Vertical direction: Supraversion (gaze moves upwards) and Infraversion (gaze moves downwards)
      • Cycloversion: Dextrocycloversion (both upper corneas rotate towards the right) and Levocycloversion (both upper corneas rotate towards the left)

    Vergence

    • Eye movements in opposite directions
    • Types of vergence:
      • Convergence: both eyes move towards the midline
      • Divergence: both eyes move away from the midline
      • Supra vergence: one eye moves upwards and the other eye straight
      • Infra vergence: one eye moves downwards and the other eye straight

    Vergence Tests

    • Stereopsis: Appreciation of relative depth due to retinal disparity
    • Three main requirements for stereoscopic vision:
      • Large binocular overlap of the visual field
      • Partial decussation of the afferent visual fibers
      • Coordinated conjugate eye movements
    • Critical professions requiring stereopsis: Pilots, Policemen, Railways, Drivers, Sports, Binocular Microscopes, Surgeons, Dentist, Optometrist, Microbiologist, and Virtual Reality

    Laws of Extraocular Motility

    • Herings' Law of Equal Innervation: equal and simultaneous innervation flows to yoke muscles
    • Sherrington's Law of Reciprocal Innervation: increased flow of innervation to contracting agonist muscle and decreased flow of innervation to relaxing antagonist muscle

    Eye Movements and Muscles

    • Yoke muscles in both eyes:
      • Right gaze (Dextroversion): RLR & LMR
      • Right up gaze (Dextroelevation): RSR & LIO
      • Right down gaze (Dextrodepression): RIR & LSO
      • Left gaze (Levoversion): LLR & RMR
      • Left up gaze (Levoelevation): LSR & RIO
      • Left down gaze (Levodepression): LIR & RSO

    Motility Test - Broad H Test

    • Purpose:
      • Restriction of eye movements in different gaze positions
      • Detects non-comitant deviation (deviation is different at different gaze positions)
      • Pain/discomfort during eye movements
    • Procedure:
      • Use pen/pen torch
      • Move in a H pattern
      • Hold target at comfortable working distance
      • Instruct the subject to follow the target, not to move their head
    • Record:
      • SAFE (Smooth, Accurate, full and Extensive)
      • Full, free, painless
      • Compare palpebral aperture size/scleral show
      • Ask for:
        • Diplopia (subjective), at any gaze
        • Pain or discomfort (subjective), at any gaze

    Fixations, Saccades & Pursuits

    • Fixation:
      • Ability to maintain a steady fixation on a fixation target
      • Symptoms:
        • Loses place when reading
        • Skips words when reading
        • Reads same line/letters twice or skips a line
        • Excessive head movement while reading
        • Poor ability to copy from whiteboard
        • Misaligns columns of numbers
        • Repeats letters within words
      • Procedure:
        • Observation of fixation for 10 sec
        • Target used: accommodative target- pen, picture
        • Look for stability or refixations
    • Saccade:
      • Redirect the eyes fixation from one target to another
      • Conjugate eye movement, e.g., reading
      • Testing Procedure:
        • Harmon distance or at 30-40 cm
        • Two targets at 10cm apart from midline
        • NSUCO grading
      • Recommended test: NSUCO Grading scale
        • Rate the performance in 4 categories:
          1. Ability
          2. Accuracy
          3. Head movements
          4. Body movements
    • Pursuits:
      • Test the ability of following eye movements
      • Helps to track a moving object in the environment, e.g., follow a tennis ball
      • Testing Procedure:
        • Working distance 30-40cm
        • One target – move in a circle of 20cm diameter
        • Two clockwise and two anticlockwise directions
        • Test performed in standing position to look for body movements
      • Recommended test: NSUCO grading scale
        • Rate the performance in 4 categories:
          1. Ability
          2. Accuracy
          3. Head movements
          4. Body movements

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    Description

    Learn about the six muscles controlling eye movements, including recti and obliques, and the cranial nerves that control them. Understand the different types of eye movements, including ductions, versions, and vergence.

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