EOM test

OPHTHALMOLOGY

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.

3. Superior view of the right globe showing muscle insertions (LPS removed). Lateral view of the right globe showing muscle insertions (LR partly removed).

4. 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.

5. 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).

6. 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 ).

7. Testing EOM The six cardinal positions of gaze

8. 9 positions of Gaze 1 ry position Elevation Depression Dexteroversion Dexteroelevation Dexterodepression Laevoversion Laevoelevation Laevodepression

9. Thanks