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Extraocular muscles.pptx
The document discusses the anatomy and function of the extraocular muscles (EOM), which control eye movement and are innervated by specific cranial nerves. It describes the arrangement of these muscles in a conic structure known as the 'annulus of Zinn' and outlines their blood supply and muscle actions. Additionally, it provides definitions and distinctions between different types of eye movements including ductions, versions, and vergences.
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Extraocular muscles.pptx
- 2.
- 3. Extraocular Muscles Theeyeballs are moved by 6 extrinsic muscles, attached at one end to the eyeball and at the other to the walls of the orbital cavity. There are 4 straight and 2 oblique muscles. Movement of the eyes to look in a particular direction is under voluntary control but co-ordination of movement needed for convergence and accommodation to near or distant vision, is under autonomic control. Purpose: To control the movement of the globe
- 5. Anatomical Arrangement All ofthe extraocular muscles form a “cone within the bony orbit with the exception of the inferior oblique. This conic structure is known as the “annulus of Zinn.”
- 6. Blood Supply The eye'smajor blood supply comes from the ophthalmic artery. The lateral muscular branch of ophthalmic artery supplies the lateral rectus, superior rectus, and superior oblique muscles. The medial muscular branch supplies the inferior rectus, medial rectus, and inferior oblique muscles.
- 7. EOM Innervations Each EOMis innervated by a specific cranial nerve (CN): Medial rectus (MR): CN III Lateral rectus (ER): CN VI Superior rectus (SR): CN III Inferior rectus (IR): CN III Superior oblique (SO): CN IV Inferior oblique (IO): CN III SO4 (LR6) 3
- 8. EOM Origin Course Insertion Action
- 9. Muscle Length of active muscle (mm) Origin Anatomic insertion Direction ofpull Innervation Medial Rectus 40 Annulus of Zinn 5.5 mm from Medical limbus 90o Lower CN III Lateral Rectus 40 Annulus of Zinn 6.9 mm from Lateral limbus 90o CN VI Superior Rectus 40 Annulus of Zinn 7.7 mm from Superior limbus 23o Upper CN III Inferior Rectus 40 Annulus of Zinn 6.5 mm from Inferior limbus 23o Lower CN III Superior Oblique 32 Orbital apex above annulus of Zinn Posterior to Equator in Supero-temporal Quadrant 51o CN IV Inferior Oblique 37 Behind lacrimal fossa Muscular area 51o Lower CN III
- 10. Medial Rectus Main Action: Adduction Innervation: InferiorDivision of Oculomotor Nerve C Temporal Nasal C
- 11.
- 12. Temporal Nasal C 23° Superior Rectus MainAction: Supraduction Secondary Action: Incycloduction adduction Innervation: Sup. Division of Oculomotor Nerve (i.e. III Cranial Nerve)
- 13.
- 14. Inferior Rectus Main Action: Infraduction SecondaryAction: Excycloduction Adduction Innervation: Inferior Division of Oculomotor Nerve Temporal Nasal C 23°
- 15. Superior Oblique Main Action: Incycloduction SecondaryAction: Infraduction abduction Innervation: Trochlear Nerve C Temporal Nasal C 51°
- 16.
- 17. Inferior Oblique Main Action: Excycloduction SecondaryAction: Supraduction Abduction Innervation: Inferior Division of Oculomotor Nerve C Temporal Nasal C 51°
- 18.
- 20. A way toremember All obliques Abduct All Recti Adduct except LR All superior muscles Intort All inferior muscles Extort
- 21.
- 22. As the eyeturns around the vertical axis,(Z) the visual axis sweeps along the horizontal plane.
- 23. As the eyeturns around the horizontal axis, (X) the visual axis sweeps along the vertical plane.
- 24. Intortion and extortionrefer to rotation around the visual axis, Y-axis Intortion refers to a nasal rotation from the 12 o'clock position. Extortion refers to a temporal rotation from the 12 o'clock position.
- 25. Nine Position OfGaze
- 26. R L RLR LMR RMR LLR RSR LIO RIO LSR RIR LSO RSO LIR The DiagnosticPositions of Gaze
- 27. Ocular movements Agonist-Antagonist: Musclesof the same eye that move the eye in opposite directions. 1. The Agonist is the primary muscle moving the eye in a given direction. 2. The Antagonist acts in the opposite direction to the agonist. e.g. Rt- LR and Rt- MR
- 28. 3. Synergist: Muscles ofthe same eye that move the eye in the same direction. e.g. Rt-SR and Rt-IO acts synergistically in elevation. 4. Yoke Muscles: Pairs of muscles, one in each eye, that produce conjugate ocular movements. Ocular movements
- 29. RSR LIO RIO LSR RIR LSO RSO LIR RLR LMR RMR LLR Yoke Muscles R L Medial Rectus Lateral Rectus Lateral Rectus Medial Rectus Superior Rectus Inferior Oblique Superior Oblique Inferior Rectus Inferior Oblique Superior Rectus
- 30. Ductions Versions Vergences Ocular movements
- 31. Definition: monocular eye movementsaround the axis of Fick, consisting: Adduction Abduction Elevation Depression Torsion Ductions
- 32. Versions Definition: These are binocular,simultaneous, conjugate movements. e.g. Positions of gaze Vergences Definition: These are binocular, simultaneous, disjugate movements. e.g. Convergence Divergence Versions and Vergences
- 33. Clinical orthoptics(FionaJ. Rowe) Diagnosis and management of ocular motility (Alec M. Ansons and Helen Davis) References
- 34. 1. All EOMSform a cone within the bony orbit except: a) Inferior oblique b) Superior oblique c) Superior rectus d) inferior rectus 2. Secondary angle of deviation will be: a) Smaller than primary angle of deviation b) Greater than primary angle of deviation c) Equal to primary angle of deviation d) None of the above MCQs
- 35. 3. Versions are: a)Binocular, simultaneous, disjugate eye movements b) Uniocular, simultaneous, disjugate eye movements c) Binocular, simultaneous, conjugate eye movements 4. Superior oblique is supplied by: a) Third nerve b) Fourth nerve c) Sixth nerve 5. Length of superior oblique muscle: a) 42 mm b) 40mm c) 32mm