Range of Movement and Ocular Alignment

January 6, 2018 | Author: Anonymous | Category: Science, Health Science
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NANOS Skills Transfer Session Gaze Testing / Rucker and Thurtell (handout created by R. John Leigh, M.D.)

Range of Movement and Ocular Alignment • Establish range of motion with ductions (one eye viewing) and versions (both eyes viewing) – Limited upgaze in elderly is due to orbital mechanical factors • If patients complains of diplopia, confirm that it is binocular • Maddox rod (cooperative subjects) or cover tests • Is a vertical deviation due to fourth nerve palsy or skew? – Superior oblique palsy: Bielschowsky head-tilt test positive – Skew deviation may decreased when subject lies supine (A.Wong) – Alternating skew with cerebellar disease: abduction hypertropia

NANOS Skills Transfer Session

Visual Fixation • Before formal gaze testing, with eyes in central position, look for nystagmus or uncalled-for saccades, by: – Simple visual inspection – Ophthalmoscope – Frenzel goggles or high positive lens in darkness/flashlight • In eccentric gaze: Look for gaze-evoked nystagmus (will affect interpretation of smooth pursuit), and then rebound nystagmus • Determine the position of the eyes under closed lids by noting corrective movements when patients open their eyes (e.g., lateropulsion in Wallenberg's syndrome)

NANOS Skills Transfer Session

Saccades Test (horizontal and vertical): – Spontaneous saccades (e.g., during conversation) – Saccades to non-specified targets – “Look right, left, up, down” – Saccades between two fixed visual targets – e.g., “pen, nose” – Rapid self-paced saccades between two fixed targets – Antisaccades – Eye-head saccades between two fixed visual targets – Quick phases of optokinetic or rotational nystagmus Note: – Initiation (prolonged reaction time, need to blink or make head movement) – Speed (distinct from range of movement) – Accuracy (look for corrective saccades indicating hypo- or hypermetria) – Trajectory (“round-the-houses” sign) – Conjugacy (especially adduction slowing – “lag” – in INO)

NANOS Skills Transfer Session Gaze Testing / R. John Leigh, M.D.

Smooth Pursuit and Eye-Head Tracking - 1 • Instruct the patient to track a small moving target smoothly, horizontally and vertically; start slowly and progressively increase speed • Look for corrective saccades that indicate an inappropriate smooth pursuit gain: – If pursuit is deficient (low gain), corrective saccades will be catch-up – If pursuit is too fast (increased gain), corrective saccades will be back-up – If pursuit is in wrong direction, corrective saccades (off-axis) • Use a small optokinetic drum or tape: – To bring out pursuit asymmetries – To detect “inverted” optokinetic nystagmus in congenital nystagmus • Use a large mirror to induce smooth tracking in uncooperative patients

NANOS Skills Transfer Session

Smooth Pursuit and Eye-Head Tracking - 2 • Assess active, smooth eye tracking, looking for corrective saccades • Test cancellation/suppression of the vestibulo-ocular reflex by rotating the patient in a chair while attempting to fixate a target moving with their head: – Look for corrective saccades – Useful to evaluate smooth tracking in patients with gaze-evoked nystagmus

NANOS Skills Transfer Session

Vergence • Note that during natural behavior, we combine vergence with saccades • There are two main stimuli to convergence – disparity (fusion) and accommodative (near) • Conventional testing combines disparity and accommodative stimuli by asking patients to fixate a target brought in along the mid-sagittal plane toward the bridge of their nose • To test vergence to accommodation: With one eye covered with a semi-opaque Spielmann occluder, the other eye alternately fixes upon near and distant targets aligned on this viewing eye. Note movements of eye under cover. • To test vergence to disparity: Place a prism in front of one eye; then remove it. • Note pupillary changes during vergence movements

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