Ocular Motility: Lecture 1: Introduction to Eye Movements

Question 1

Why do we need eye movements?

1. Pre-requisites for a steady image:
   a. An image needs to be held steady. What is this called?
   b. Where should objects be close to? (what area of the brain)
2. Anatomical considerations….to follow what?
3. Vergence Eye Movements: Does 2 things?
4. Versional Eye Movements: Tracks Objects how?

Answer 1

1. a. Oscillopsia
   b. the Fovea
2. To Follow moving Objects
3. Track Objects in Depth and Provide Stereopsis
4. Track Objects Laterally

Question 2

Functions of the Oculomotor Systems

1. Eye movements expand the regions of space so that we have HIGH what?
2. Accommodation expands the range of distances that enable us to have 2 things? (From what distance?)
3. Pupil size is normally adjusted to give us an ability to regulate light level by a factor of what?
4. Having frontally placed eyes has the benefit of allowing what to occur?
   a. What is the disadvantage though?
5. Eye movements also allow us to stabilize our VF and to stabilize images of what?

Answer 2

1. HIGH RESOLUTION
2. to have HIGH ACUITY and CLEAR Vision (from 5 cm to Optical Infinity)
3. by a factor of 10.
4. Allowing STEREOPSIS to occur.
   a. it reduces our VF from 360 degrees to about 180 degrees
5. images of moving objects

Question 3

4 Types of Eye Movements.

What are they?

Answer 3

1. Saccade
2. Pursuit
3. Vergence
4. VOR and OKN

Question 4

Classification of Eye Movements

1. Saccade: Define
2. Pursuit: Define

Answer 4

1. Eye movements that PLACES the IMAGE on the FOVEA!!

2. Slow Eye Movements that MAINTAIN the IMAGE on the FOVEA

Question 5

Classification of Eye Movements

1. Conjugate/Version: Define
2. Disconjugate/Vergence: Define

Answer 5

1. They move in the SAME DIRECTION

2. Move in OPPOSITE DIRECTION

Question 6

Saccadic Eye Movements

1. Fast eye movements reaching what speed?
2. Voluntary or Involuntary?

Answer 6

1. Reaching 10,000 degrees/sec

2. made voluntarily with different stimuli

Question 7

Pursuit Eye Movements

1. What does it maintain with the image?
2. Voluntary?

Answer 7

1. image on the Fovea

2. Usually cant be made voluntarily

Question 8

Vergence Eye Movements

1. Shifts the image b/w what 2 things?
2. Responds to what?

Answer 8

1. Distance and Near

2. responds to a BROAD range of stimuli

Question 9

Eye Movements

1. Vestibulo-Ocular Reflex (VOR): Compensates for what 2 things?
   a. Controls what about image stabilization?
   b. What does it respond to?
2. Optokinetic Nystagmus (OKN): This reflex requires what?
   a. What does it do about Image Stabilization?
   b. Constant what?

Answer 9

1. for Brief Head and Body Rotation
   a. Initial Image stabilization
   b. Acceleration and Deceleration
2. Reflex that requires a VISIBLE RETINAL IMAGE
   a. Maintains the Stabilization
   b. Constant Retinal Image Velocity

Question 10

Eye Movements

1. VOR: When head movement occurs, what System is triggered and what does this System Signal about the head?
   a. What other system is triggered and what does it do to compensate?
   b. This leads to what Movement type?

Answer 10

1. Semicircular Canals of the Vestibular System. It Signals HOW FAST the HEAD IS ROTATING!
   a. The Oculomotor System; Rotates the Eye in an EQUAL and OPPOSITE VELOCITY
   b. Leads to the Vestibulo-Ocular Reflex (VOR)

Question 11

Eye Movement Classification

1. Speed
   a. Fast: What 2 movement types?
   b. Slow: What movement type?
2. Conjugacy: What 2 types?
3. Direction: What 4 types?

Answer 11

1. a. Saccade and Vergence Eye Movements
   b. Pursuit
2. Version and Vergence
3. Depression, Elevation, Hyper/Hypo
   * Also Torsion

Question 12

Eye Movements

1. Adduction: Rotation around what Axis?
   a. Eye moves how?
2. Abduction: Rotation around what Axis?
   a. Eye moves how?
3. Supraduction: Rotation around what?
   a. Eye does what?
4. Infraduction: Rotation around what?
   a. Eye does what?

Answer 12

1. Vertical Z Axis. (Medial rotation)
   a. Eye moves TOWARDS nose
2. Around Vertical Z Axis (Lateral)
   a. Eye moves AWAY from the Nose
3. Rotation upwards around the Horizontal X-Axis
   a. Eye Elevates
4. Downward rotation alond the Horizontal X-Axis
   a. Depresses the eye

Question 13

Eye Movements

1. Z-Axis: used for what eye movements
2. X-Axis used for what eye movements?
3. Y-Axis used for what eye movements?

Answer 13

1. Abduction and Adduction
2. Incyclotorsion and Excyclotorsion
3. Elevation and Depression

Question 14

Kinematics of Eye Movements

1. Globe: It’s a Sphere rotating about what?
2. Primary Position: Position of the eyes when the head is in what position?
   a. It’s the position from which a Pure Horizontal or Vertical Movement is NOT ASSOCIATED with any what?
3. Secondary Position: Position of they Eyes when either a Purely Horizontal/Vertical Movement is made from what?
   a. So the Eye rotates about what ONLY?
   b. There is NO what?

Answer 14

1. about a Point Fixed w/in Itself
2. When it’s Erect, and the 2 eyes are fixating into the INFINITE DISTANCE along a Horizontal Plane
   a. with any Tilt
3. from PRIMARY POSITION
   a. a Vertical or Horizontal Axis only

b. NO ASSOCIATED TILT of the Vertical Meridians of the Eyes w/Respect to Objective Vertical

Question 15

Kinematics of Eye Movements

1. Tertiary Position: Position of the Eyes when they Move from Primary Position to what?
2. Torsion: Define
3. False Torsion: Apparent Cyclorotation of the Eye Associated w/a Change in Direction of Regard from what?
   a. The Angular Difference b/w the Objective Vertical and what?

Answer 15

1. to Anywhere BUT a Secondary Position
2. TRUE CYCLOROTATION about an ANTERO-Posterior Axis, like LINE-OF-SIGHT
3. from Primary Position to some Tertiary Position
   a. and the Vertical Corneal Meridian when they Eye is in a Tertiary Position

Question 16

Donder’s Law

1. States that for ANY 1 Gaze Direction, the Eye Always assumes what?
   a. The Orientation is Always the same, IRRESPECTIVE of what?

Answer 16

1. the Same Unique Orientation in 3 Dimensions

a. Irrespective of where the Eye came from

Question 17

Listing’s Law

1. All Achieved Eye Orientations can be reached by starting from 1 SPECIFIC PRIMARY Reference ORIENTATION and then doing what?
2. Listing’s Plane: a Plane Passing thru the HEAD and the CENTER of Rotation of the Eyes that is what?

Answer 17

1. then Rotating about an AXIS that LIES w/in the PLANE ORTHOGONAL to the PRIMARY ORIENTATIONS GAZE DIRECTION (line of sight/visual axis)
2. is Perpendicular to the line of sight when the eyes are in primary position

Question 18

Hering’s Law of Equal Innervation

1. Refers to interactions b/w what 2 things?
2. Innervation of CNS –> what muscles –> ?

Answer 18

1. B/w Contralateral Agonists or Synergists
2. to 2 Different Muscles –> Eye Movement in the SAME DIRECTION

(Look to the right…use RLR and LMR)

Question 19

Sherington’s Law of Reciprocal Innervation

1. Opposing Muscles are what?
2. What applies to the MR and LR also applies to what other muscles?
3. When an Agonist Contracts during movement of an Eye, there’s a Simultaneous and EQUAL Relaxation of what?

Answer 19

1. RECIPROCALLY INNERVATED
2. SR & IR, and to the SO & IO
3. of its ANTAGONIST fellow muscle. ie, RLR contracts, and RMR Relaxes.

Question 20

1. The Versional System Controls what movements of the eye?

2. Vergence system controls what?

Answer 20

1. Conjugate movement. So, movement of EYES in the SAME DIRECTION, to see objects positioned in various directions from us.
2. Disjunctive Movements of the eyes. So, Movement of the Eyes in Opposing Directions to see objects Singly at different distances from us.

Question 21

Retinal, Ocular and Combined Head and Body movements PRIMARILY Stimulate what 4 systems and what do each do?

Answer 21

1. Saccadic System (to try and get Foveation)
2. Pursuit System (Match Eye velocity to velocity of the smoothly moving target)
3. Vestibular System: Stabilize gaze during the initial (about 30 seconds) and Transient phase of Head and Body rotation
4. Optokinetic system (Stabilize gaze during the later, SUSTAINED phase of head and body rotation)