EOM test
- 1. OCCULAR MOTILITY TESTING BY DR. ALSHYMAA MOUSTAFA OPHTHALMOLOGY SPECIALIST
- 2. ANATOMY • The orbit forms a pyramid in which the lateral and medial walls are at 45* to each other, and the central axis is thus at 22.5* (approximated to 23*). • The superior oblique (SO; like the levator palpebrae superioris) originates from the orbital apex outside the annulus; in contrast, the inferior oblique (IO) arises from the nasal orbital fl oor. • The obliques lie inferior to their corresponding rectus (R) muscle (i.e., SO lies inferior to SR and IO inferior to IR). • The spiral of Tillaux describes the way the recti insert increasingly posterior to the limbus (MR, IR, LR, then SR). • Innervation is by CN III for SR, MR, IR, IO; by CN IV for SO; and by CN VI for LR.
- 4. Superior view of the right globe showing muscle insertions (LPS removed). Lateral view of the right globe showing muscle insertions (LR partly removed).
- 5. PHYSIOLOGY (EYE MOVEMENTS) • Eye movements may be monocular (ductions) or binocular (versions and vergences). • Versions are conjugate eye movements, i.e., both eyes move in the same direction, whereas vergences are disconjugate, i.e., both eyes move in opposite directions. • Eye movements may be described as rotations of the globe around horizontal (x), anteroposterior (y), and vertical (z) axes—the axes of Fick.
- 6. • Ductions comprise abduction (outward), adduction (inward), supraduction (upward), infraduction (downward), intorsion (superior limbus moves inward), and extorsion (superior limbus moves outward). • Versions include dextroversion (right gaze), levoversion (left gaze), supraversion (upgaze), infraversion (downgaze), dextrocycloversion (superior limbus moves right), and levocycloversion (superior limbus moves left). • Vergences include convergence (inward) or divergence (outward).
- 7. • The extraocular muscles do not act in isolation. • Each agonist (e.g., LR) has an antagonist that acts in the opposite direction in the same eye (i.e., ipsilateral MR). • Increased innervation of the agonist is accompanied by decreased innervation of its antagonist (Sherrington’s law). • Each agonist also has a yoke muscle that acts in the same direction in the other eye (i.e., contralateral MR in this example). • During conjugate movement yoke muscles receive equal and simultaneous innervation (Hering’s law).
- 8. TESTING EOM The six cardinal positions of gaze
- 9. • 9 positions of Gaze 1. 1ry position 2. Elevation 3. Depression 4. Dexteroversion 5. Dexteroelevation 6. Dexterodepression 7. Laevoversion 8. Laevoelevation 9. Laevodepression
- 10. THANKS