Eye Movements 2 Flashcards Preview

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Flashcards in Eye Movements 2 Deck (13):
1

A smooth pursuit eye movement is elicited by:

any large moving stimulus, and it is an attempt to foveate that stimulus for more extended visual examination.

Once the object is on/near the fovea, slower movements (pursuit) are used to track the moving object.

2

Smooth pursuit eye movements can only maintain foveation at a rate of ____. Why?

50 degrees per second or less.

Coordinating smooth pursuit requires a lot of analysis in the visual cortex.
You analyze the position, direction of movement and speed in the visual cortex, and this takes time.
At a speed greater than 50 degrees per second, the visual cortex cannot keep up, and so saccades are initiated at points during smooth pursuit to "catch up" with the object

3

At a speed greater than 50 degrees per second, the visual cortex cannot keep up, and so saccades are:

initiated at points during smooth pursuit to “catch up” with the object.

4

VOR =

1. Fast and Accurate
2. Can occur in the dark w/o any visual stimulus

5

VOR is driven by

vestibular input

6

There are _____ for all directions of head rotation.

corresponding head-eye compensations

However many degrees your head moves in one direction, the eyes must move a corresponding amount in the opposite direction to maintain fixation on a certain point in space.

7

Rightward head rotation is signaled by the

horizontal canals.

8

nystagmus

1. if the head turns to the right, the eyes counter rotate left.
2. If the head continues to turn, the eyes rotate slowly left until the limit of eye rotation is reached, then snap quickly back to a new fixation point.
3. The sawtooth movement of the eyes – slow ramp opposite to head rotation, fast saccade to center of eye position

9

The direction of nystagmus is determined by

the direction of the rapid saccade “right-beating nystagmus”

10

Internuclear opthalmoplegia describes

the disconnection of the coordination of medial and lateral recti during horizontal gaze movements due to MLF damage.

early sign of MS

11

The MLF is

large, long, and myelinated. As such, it is vulnerable to demyelinating diseases, such as MS.

12

Internuclear opthalmoplegia:
The medial rectus muscle and motor neurons may be normal even though

the muscle does not function properly during horizontal gaze. You can tease this out by doing a vergence test.

13

If a patient is unable to participate in horizontal gaze saccades or pursuit, yet can perform convergence eye movements:

then the patient likely has internuclear opthalmoplegia

(as opposed to, for example, CN III palsy).