Ocular Motility: Lecture 14: Recording Eye Movements

Question 1

Techniques for recording eye movements? (8)

Answer 1

1. DO
2. Electro-Ocular Graph (EOG)
3. External Photograph
4. Gross-visual Obervation
5. High Magnification Biomicroscopy
6. Infrared Limbal Reflection
7. Magnetic Search Coil
8. Video-based Eye Tracker

Question 2

Direct Observation

1. Quantitative?

Answer 2

1. No. non-quantitative, just DESCRIPTIVE and VERY HARD to QUANTIFY

Question 3

External Photography

1. What is it?

Answer 3

1. Photographic Documentation of Pre and Post Treatment

Question 4

High Magnification Video

1. These offer what?
2. Used for Objectively doing what?

Answer 4

1. Good resolution Capability
2. Documenting and evaluating less obvious Fixational Eye Movement Abnormalities (about 1 degree), such as increased Amblyopic drift, as well as strabismus related saccadic intrusions and small-amplitude jerk nystagmus, especially before and after vision therapy

Question 5

Direct Ophthalmoscopy (1)

1. With this technique, target displacements on the retina as well as the resultant eye movement(s) can be what?
2. Both Fixational Dynamics (such as saccadic overshoot and nystagmus) and time-averaged fixational locus (like eccentric fixation/viewing) can be what?

Answer 5

1. visualized and assessed directly

2. can be evaluated

Question 6

Direct Ophthalmoscopy (2)

1. Due to High Mag of the System Optics (-16x), it’s an easy way to assess what things?
2. A Focused target is projected onto what?
   a. If the target and head are held stationary, then fixation can be what?
   b. If head is rotated, what can be directly visualized?
3. IF the target is either suddenly displaced (STEP INPUT) or slowly and smoothly moved (Ramp input), then what can be evaluated?
   a. Resolution with this technique is what?

Answer 6

1. Monocular fixation as well as Saccadic, pursuit, vestibular ability, especially in peeps w/amblyopia and in patients w/CNS disorders
2. onto the patient’s Central Retina
   a. can be assessed
   b. Vestibular Function
3. then saccadic and pursuit function, respectively, can be evaluated
   a. is 0.5 degrees or better

Question 7

Electrooculography

1. Change in electric field potential with eye movement can be exploited to obtain an Objective record of change in what?
2. EOG technique depends on what?
   a. Electrical Potential Difference of what?

Answer 7

1. in Horizontal Eye Position
2. on Voltage difference or electrical potential difference b/w Anterior and Posterior Pole of the Eye.
   a. 10-20 millivolts b/w the 2 poles

Question 8

Electrooculography

1. Advantages

Answer 8

1. measure +/- 70 degrees of movement
2. Easy to set up
3. Can be used to assess horizontal and vertical eye movement
4. DOESNT obstruct the field of view

Question 9

Electrooculography

1. Disadvantages

Answer 9

1. Noisy
2. System resolution is more than 1 degree
3. Changes in light adaptation can influence the signal

Question 10

Magnetic Scleral Coil Technique

1. How are Eye movements measured?
2. Alternating Magnetic Fields are generated by what?
3. Thru Electromagnetic Induction, electric currents are generated in search coils. The Polarity and Amplitude of the current generated varies w/what?
4. By measuring these values, what can be determined?
5. TEMPORAL RESOLUTION as fast as what?
6. what is GOOD?

Answer 10

1. using coils that are embedded into a tightly-fitting contact lens
2. by Magnets positioned around the eye
3. w/the direction and angular displacement of the eye
4. the position of the eye can be determined
5. as 1000 Hz
6. SPATIAL RESOLUTION is GOOD

Question 11

Infra Red Limbal Reflection (1)

1. KNown as what?
2. A Low-wattage infrared source does what?

Answer 11

1. Photocell, Photodiode, Photoelectric, Scleral Reflection, and Limbal Tracking System
2. diffusely illuminates the entire exposed anterior surface of the eye,

OR

primarily its nasal and temporal horizontal limbal regions

Question 12

Infra Red Limbal Reflection (2)

1. Light sensitive Diode that varies its resistance as it receives light. This variation in Resistance shunts various amts of voltage and it’s possible to get what?
2. Can be used to what degree of gaze?
3. Problem?
4. It has a resolution of AT LEAST what?

Answer 12

1. to get a Voltage Analog of Eye Position
2. +/- 20 degrees of gaze
3. Eye lid interference
4. 0.25 degrees over a linear range of at least +/- 7.5 degrees

Question 13

Video Based Eye Trackers (1)

1. These devices analyze the image of what?

Answer 13

1. the Corneal Light Reflex and Pupil Center

Question 14

Video Based Eye Trackers (2)

1. Track the change in shape of the the pupil and the displacement of the center of the pupil or what?
2. Can combine the position of the eye w/the scene viewed by the subject to indicate where in the scene someone is what?
3. Easier to record what?
4. Can be used how?

Answer 14

1. or Position of the Corneal Light Reflex
2. is Fixating
3. Horizontal, Vertical, and Oblique
4. Remotely