Ocular Motility: Lecture 15: Clinical Evaluation of Eye Movements Flashcards
1
Q
Fixation (1)
- Oculomotor Evaluation should start with the assessment of what?
a. With emphasis on what?
A
- of FIXATION
a. on Performance in PRIMARY GAZE
2
Q
Fixation (2)
- FIXATION should be tested where?
a. Why is this?
b. At Distance: What can we use?
c. At Near?
A
- at BOTH DISTANCE and NEAR
a. Nystagmus characteristics may change considerably w/viewing distance and vergence demand or innervation.
b. use a Muscle light or a Snellen Letter 1 or 2 lines above Pt’s Threshold VA and positioned along the patient’s midline as a target
c. Snellen Letter should be held along the patient’s midline at 40 cm
3
Q
Fixation (3)
- Under what VIEWING CONDITIONS should fixation be assessed?
a. Why?
b. What do we use to Reveal MAXIMUM of FIXATION DISORDER?
A
- MONOCULAR and BINOCULAR VIEWING CONDITIONS
a. Monocular fixation characteristics can differ greatly from those found during Binocular Fixation (ie, pure latent nystagmus: a normal movement under conditions of binocular fixation transforms into a JERK NYSTAGMUS w/Fast Phase in the direction of the viewing eye during Monocular Fixation)
b. COMPLETE OCCLUSION
4
Q
Fixation (4)
- Fixation should ALSO BE ASSESSED in what positions of gaze?
a. Why?
b. What is the Objective here?
c. A Patient w/Left-Jerk Nystagmus (Fast Saccadic Phase to the Left) will typically Exhibit what?
A
- SIX DIAGNOSTIC POSITIONS of GAZE
a. Best isolate the Action of Each of the 6 EOMs
b. Determine whether there are CONGENITAL OVERACTIONS or UNDERACTIONS, or ACQUIRED PARESES, of the EOMs
c. a NULL Position to the RIGHT of PRIMARY GAZE
5
Q
Abnormal Drift
- What is it?
- Typically Exhibits an AMPLITUDE of what?
a. With a VELOCITY of what? - What is the ONLY way to DIAGNOSE this Abnormal Drift w/o Objective Eye Movement Equipment?
- What will Abnormal Drift appear as?
A
- Common finding in Functional Amblyopia
- of up to 1 DEGREE or so
a. of UP TO 3 DEGREES/SEC - is with LOWLIGHT VISUOSCOPY
- Random slow movements away from the Fixation Locus, Occasionally interrupted by a Saccade (Either Error-correcting or error producing), as well as error-correcting drift
6
Q
Nystagmus: Congenital
- Up Gaze
- Null Point
- Convergence
- Head Turn or Tilt
- Oscillopsia
- Associated with what 2 things?
A
- H. Nystagmus
- Common
- Dampens
- Common
- None
- Albinism, and Achromatopsia
7
Q
Nystagmus: Acquired
- Up Gaze
- Null Point
- Convergence
- Head Turn or Tilt
- Oscillopsia
- Associated with what 2 things?
A
- May convert to up-beat nystagmus
- None
- Usually no effect
- Less Common
- Always Present
- Multiple Sclerosis
8
Q
Nystagmus
- When evaluating a Pt using DO w/a Projected Target, what will a JERK NYSTAGMUS APPEAR TO DO?
A
- It appears as a “Sliding” movement AWAY from the FIXATIONAL GRID CENTER, w/a RAPID and JERKY Corrective (SACCADIC) Foveating movement back to central fixation
9
Q
Nystagmus (3)
- Freznel Goggels: What are they?
a. with them on, and the room lights darkened, how easy is it to see?
A
- Combo of Magnifying glasses (+20 lenses placed in front of the Patient), and a LIGHTING SYSTEM
a. nystagmus can easily be seen cuz the patients eyes are well illuminated and magnified and because fixation is removed as the patient can hardly focus thru magnifying glasses on a dark room
10
Q
VOR System (1)
- Head THRUS/IMPULSE TEST (test for Dynamic Imbalance)
a. What is the patient asked to do?
b. How do you test the Horizontal Canals?
c. What will a subject normally be able to do?
d. If VOR is defective, what will the patient not be able to do?
e. Ex?
A
- a. Fix upon a distant target
b. Examiner briskly rotates the patient’s head to the left or right
c. maintain fixation during head impulses in any direction
d. Won’t be able to maintain fixation and will need to make 1 or 2 refixating saccades
e. During leftward head impulse, patient makes a rightward saccade to maintain fixation, this indicates that the Horizontal Canal is NOT FUNCTIONING PROPERLY
11
Q
VOR (2)
- HEAD-SHAKING VA (Test for abnormal VOR GAIN)
a. Patient is asked to do what?
b. What does the examiner do while the Patient does this?
c. Normally, what will happen?
d. If VOR gain is abnormal?
A
- a. Read the SNELLEN chart
b. Rotates the head at about 2 Hz horizontally and then vertically
c. VA will decrease by 1 or 2 lines
d. VA will decrease by several lines
12
Q
OKN System
- How long do we have to allow for the OKN response to build up?
a. Where should the drum be held? - How do you stimulate Actual OKN System Maximally?
- OKN is present in what blindness?
a. What blindness is it not present?
A
- About 30 seconds
a. 20 cm from the patient - It’s necessary to have a LARGE FIELD of MOTION (like a drum) w/the patient passively looking at the stimulus
- Hysterical Blindness
a. Organic Blindness
13
Q
Saccades (1)
- How do you test Saccades?
- What 5 things do you take note of?
- Localize any saccade abnormality w/in the hierarchy of Saccades by assessing in what ORDER?
A
- Have a patient look alternately at 2 targets held apart horizontally or vertically, like an Examiner’s Finger and Nose
- Velocity, Latency, Accuracy, Trajectory, and Conjugacy
- a. QUICK PHASES: use an OKN Drum to elicit OKN. Loss of Quick phases is usually due to LESION of PREMOTOR BURST NEURONS in the BRAINSTEM
b. VISUALLY GUIDED (Reflexive) SACCADES: Present patient w/a suddenly appearing visual or auditory target
14
Q
Saccades (2)
- VOLUNTARY SACCADES to COMMAND
a. Ask the patient to do what?
b. Loss of Voluntary Saccades with Preservation of Quick Phases and Visually Guided (reflexive) Saccades is Characteristic of what? - PREDICTIVE, ANTICIPATORY SACCADES
a. How do you test this?
b. With Predictable timing, what do you do?
c. Defects of Predictive Saccadic Control are Common in what DISEASE?
A
- a. to Make Saccades Rapidly b/w 2 Stationary Targets
b. of Acquired Ocular Motor Apraxia - a. Hold both hands up and ask patient to make a saccade when 1 of your fingers moves.
b. move first a finger on one hand and then a finger on the other, and repeat this cycle several times, occasionally not moving one finger to determine if the patient makes a predictive saccade
c. Defects of Predictive Saccadic Control are common in PARKINSON’s Disease
15
Q
King-Devick Test
- It’s an Objective, Physical method of evaluating what 2 things?
- What does the patient do?
a. How are results scored?
b. Why is this a decent test?
A
- Visual Tracking and Saccadic Eye Movement
- Names sequences of digits arranged in various degrees of complexity. (Rapid number naming)
a. With respect to Total Test time and Error
b. It has more comparative data and more range in difficulty…but not a good test if patient has trouble naming numbers
