Strabismus and Extraocular Muscles
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Questions and Answers

What is the primary purpose of the cover test in the examination of a squint?

  • To check for ocular alignment by observing eye movement when one eye is covered (correct)
  • To assess ocular movements in different directions
  • To measure visual acuity in both eyes
  • To evaluate the presence of craniofacial abnormalities
  • In the management of a child with squint, which factor is NOT a part of the history taking process?

  • Direction of the squint
  • Visual assessment methods used (correct)
  • Onset of squint symptoms
  • Family history of squint
  • Which surgical approach is used to address esotropia in children?

  • Superior oblique tenotomy
  • Inferior oblique strengthening
  • Medial rectus recession (correct)
  • Lateral rectus resection
  • What type of correction is primarily focused on during the treatment of amblyopia?

    <p>Full cycloplegic correction of refractive errors</p> Signup and view all the answers

    Which testing method uses the corneal reflex to identify the alignment of the eyes?

    <p>Corneal reflection test</p> Signup and view all the answers

    What is the primary cause of visual impairment associated with strabismus?

    <p>Ocular misalignment preventing image formation on the fovea</p> Signup and view all the answers

    Which extraocular muscle is responsible for depression and extorsion of the eye when adducted?

    <p>Superior Oblique</p> Signup and view all the answers

    What type of squint is characterized by a constant angle of deviation regardless of gaze direction?

    <p>Concomitant Squint</p> Signup and view all the answers

    Which term describes the squint that is latent and can only be discovered by a cover test?

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

    Which condition is NOT a possible cause of strabismus?

    <p>Regurgitation of food</p> Signup and view all the answers

    What is the classification of strabismus according to the direction of deviation when the eye is turned outward?

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

    Which type of strabismus arises due to palsy of one of the nerves that supply extraocular muscles?

    <p>Paralytic Squint</p> Signup and view all the answers

    Which extraocular muscle is primarily responsible for adduction of the eye?

    <p>Medial Rectus</p> Signup and view all the answers

    Study Notes

    Strabismus

    • Strabismus is a misalignment of the eyes, so the image of an object does not fall on the fovea of both eyes simultaneously.
    • The image of the object formed by each eye should normally lie at its fovea (Bifoveal Imaging).
    • Six extraocular muscles insert in the sclera of each eye. These muscles allow for the coordinated movement of the eye.
    • 2-5% of the population are affected by strabismus.

    Extraocular Muscles

    • Superior Rectus: Oculomotor nerve innervates this muscle, responsible for:
      • Elevation (in adduction)
      • Intorsion
      • Adduction
    • Inferior Rectus: Oculomotor nerve innervates this muscle, responsible for:
      • Depression (in adduction)
      • Extorsion
      • Adduction
    • Medial Rectus: Oculomotor nerve innervates this muscle, responsible for:
      • Adduction
    • Lateral Rectus: Abducens nerve innervates this muscle responsible for:
      • Abduction
    • Superior Oblique: Trochlear nerve innervates this muscle, responsible for:
      • Depression (in abduction)
      • Intorsion
      • Abduction
    • Inferior Oblique: Oculomotor nerve innervates this muscle, responsible for:
      • Elevation (in abduction)
      • Extorsion
      • Abduction

    Strabismus Significance

    • Strabismus is a common problem.
    • Significant cause of visual impairment. It may be caused by or associated with:
      • Hypermetropia (farsightedness)
      • Optic Nerve Hypoplasia
      • Retinoblastoma
    • Strabismus can have a significant cosmetic and social impact.

    Classifications of Strabismus

    • Direction of Deviation:
      • Eso Deviation - Convergent squint, eye turns inward
      • Exo Deviation - Divergent squint, eye turns outward
      • Hyper Deviation - Upward deviation of one eye
      • Hypo Deviation - Downward deviation of one eye
    • Severity:
      • Tropia - Apparent squint, misalignment is always present.
      • Phoria - Latent squint, misalignment only present when one eye is covered.
      • Example: Right Esotropia - apparent convergent squint of the right eye.
    • Pathological:
      • Concomitant Squint - Angle of deviation of the squinting eye is constant in any direction.
        • Early childhood onset without correction can lead to amblyopia and loss of binocular vision.
        • Examples: Congenital Esotropia, Accommodative Esotropia
      • Paralytic Squint (Incomitant) - Caused by complete or partial palsy of one of the nerves that supply the extraocular muscles.
        • Angle of deviation is maximal in the direction of action of the weak muscle.
        • Examples:
          • Oculomotor Palsy
          • Abducens Palsy
          • Trochlear Palsy

    Management of Child with Squint

    • History:
      • Birth: Prematurity, method of delivery
      • Medical problems, developmental abnormalities
      • Age of onset
      • Direction of deviation
      • Constant or intermittent misalignment
      • Association with fatigue
      • Family history
    • Examination:
      • General Appearance:
        • Craniofacial abnormalities
        • Abnormal head posture (may be to avoid diplopia)
        • Epicanthal fold (a fold of skin at the inner corner of the eye)
      • Visual Assessment:
        • Different techniques used to assess vision
        • Assessment for amblyopia (reduced vision in one eye)
      • Corneal Reflection Test: Using a pen torch, assessing distance, symmetry, and position of the light reflection.
        • Example: If one reflection is nasally positioned, the eye is turned outward.
      • Cover Test: Performed at distance and near. Cover one eye and look for movement of the other to take up fixation. This helps determine the type and severity of strabismus.
      • Ocular Movements: Tested in different directions of gaze. Helps assess for muscle weakness, paralysis, or restriction.
      • Cycloplegic Refraction: This involves dilating the pupils with eyedrops to measure the refractive error more accurately. This is important for diagnosing and treating accommodative esotropia.
      • Dilated Fundus Examination: Examining the back of the eye, including the retina, optic nerve, and blood vessels. This is important for identifying any underlying pathology that may be causing the strabismus.

    Treatment

    • Full cycloplegic correction of refractive errors: This is important for correcting the refractive error, which can help to reduce or resolve the strabismus.
    • Treatment of Amblyopia: This is done by occluding the "good" eye to force the brain to use the weaker eye and improve visual function.
    • Surgery: This is often needed to restore alignment and achieve binocular vision. This involves strengthening or weakening procedures of the extraocular muscles.
      • Example: Esotropia (convergent squint) requires medial rectus recession and lateral rectus resection, which weakens the inward pulling muscles and strengthens the outward pulling muscles.

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    Related Documents

    Squint (Strabismus), PDF

    Description

    This quiz explores the topic of strabismus, which involves the misalignment of the eyes and its impacts on vision. It also delves into the functions and innervations of the six extraocular muscles that control eye movement. Test your knowledge on these anatomical structures and their roles in visual coordination.

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