Chapter 3 The oculomotor examination has two purposes. First, a variety of tests assess the function of supranuclear and internuclear pathways, brainstem nuclei, cranial nerves, neuromuscular junctions, and the extraocular muscles, providing a window into nervous system functioning. Specific patterns of dysfunction are seen in several different neurologic disorders, frequently without specific eye complaints. Second, oculomotor examination can address the symptom of binocular diplopia; that is, double vision with both eyes open, resolving with closure of either eye. The oculomotor exam includes determination of the range and nature of extraocular movement, ocular alignment, and whether or not nystagmus is present. One should also assess for proptosis, lid lag, lid retraction, orbicularis oculi strength, as well as cranial nerve VII and V function because this can assist the examiner in determining the etiology of or localizing an abnormality found on the oculomotor exam. There are six muscles around each eye, allowing the eye to move up, down, obliquely, or perform a torsional movement. Although the six muscles function as a single unit in moving the eye, for practical purposes we consider them as single muscles and yoke pairs. Considered as single muscles, there are (1) the lateral rectus, an abductor; (2) the medial rectus, an adductor; (3) the superior rectus, primarily an elevator, secondarily an adductor and intorter; (4) the inferior rectus, primarily a depressor, secondarily an adductor and extorter; (5) the superior oblique, primarily an intorter, secondarily a depressor and abductor; and (6) the inferior oblique, primarily an extorter, secondarily an elevator and abductor. Yoke pairs are the muscles used in each eye to produce a version. Horizontal versions require the lateral rectus of one eye and the medial rectus of the other eye to contract together. There are two vertical yoke pairs, first the superior rectus of one eye and inferior oblique of the other eye, and second the inferior rectus of one eye and the superior oblique of the other eye. deviation A misalignment between the two eyes so that they are not aligned with the same target. tropia A manifest deviation of the eye; that is, one that is present with the eyes open and fixating. In patients with normal vision in both eyes and no amblyopia, a tropia results in diplopia. This can best be measured with the cover–uncover test (see later in this chapter). phoria A latent deviation of the eyes; that is, the misalignment is only seen while an eye is covered, disrupting fusion of the eyes. This is usually done with the alternate cover test (see later in this chapter). esotropia/esophoria One eye is deviated nasally relative to the other. An esotropia is seen without covering the eye, whereas an esophoria is seen if either eye is covered (either a manifest or latent deviation). exotropia/exophoria One eye is deviated temporally relative to the other. hypotropia One eye is deviated downward, relative to the other. hypertropia One eye is deviated upward, relative to the other. comitant deviation The deviation is quantitatively the same in all positions of gaze. incomitant deviation The deviation varies with gaze position, for example, the esotropia in a right sixth nerve palsy is incomitant; it is greatest in right gaze and least in left gaze. duction Movement of a single eye in one direction; for example, adduction is movement of an eye toward the midline; abduction is movement away from the midline; elevation, or supraduction, is movement upward; depression, or infraduction, is movement downward. torsion Rotation around an axis line connecting the center of the cornea with the fovea. Intorsion, or incycloduction, refers to rotation of the upper eye toward the nose. Extorsion, or excycloduction, refers to rotation of the upper eye toward the ear. version Conjugate movement of both eyes in a single direction. pursuit Smooth movements of the eye, used for tracking a moving object. saccade Extremely rapid movements of the eye from one point to another, which may be either voluntary or reflexive. When saccades are abnormal, they may be slow and/or hypermetric (overshooting their target) or hypometric (undershooting their target). Begin the oculomotor exam by asking the patient to fixate on a light source held by the examiner directly in front of the patient (primary position). Fixation should be steady (if not, see Chapter 10). Ocular alignment may be checked by observing the corneal light reflexes. If the eyes are aligned normally, the light reflexes should appear in the center of each pupil. If a misalignment is present, the light reflex appears in the center of the pupil of the eye that is fixating on the light source, whereas it appears eccentrically in the contralateral eye, for example, nasally if the eye is exotropic and temporally if the eye is esotropic.
TECHNIQUES OF THE OCULOMOTOR EXAMINATION
EXTRAOCULAR MUSCLE ANATOMY
DEFINITIONS
FIXATION AND ALIGNMENT
EXTRAOCULAR MOVEMENTS
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