Week 3 Eye Movements and Vision

Question 1

What is a Saccade

Answer 1

It is the rapid repositiong of the eye. Rates can reach up to 900degrees/s

Question 2

Are saccadic eye movements driven by our intentions or the visual stimuli in our environment?

Answer 2

Our intentions. They are all goal-directed for example, when reading a book, preparing a sandwich etc.

Question 3

When an object moves relatively slowly with respect to the head, the eyes can follow the object without interruption. What is this called?

Answer 3

Smooth Persuit

Question 4

When you shift your optical attention from something far to something close, or vice versa, what type of movement is this?

Answer 4

Vergence

Question 5

What is Vestibulo-ocular reflex? What does it do?

Answer 5

Detects the movement of the head in space using the vestibular system. VOR eye movement corrects for head movement.

Question 5

What is Vestibulo-ocular reflex? What does it do?

Answer 5

Detects the movement of the head in space using the vestibular system. VOR eye movement corrects for head movement.

Question 6

How does the VOS correct the head position?

Answer 6

Head movement causes the liquid in the 3 semicircular canals to move, which causes tiny sensory hair cells to bend.

Question 7

What’s the Optokinetic Reflex movement? How does it happen?

Answer 7

Happens when an object in the environment moves. If you track a moving object and moves out of your field, the eyes will jump back to the starting point. This process is relatively sluggish

Question 8

What does both vestibular and optokinetic stimulation generate? What is it? give an example.

Answer 8

Nystagmus. A sawtooth response with slow eye movements interrupted by fast repositioning. for example, when you spin on an office chair while repeatedly fixating on a point in your environment that disappears out of view due to your movement.

Question 9

What does both vestibular and optokinetic stimulation generate? What is it? give an example.

Answer 9

Nystagmus. A sawtooth response with slow eye movements interrupted by fast repositioning. for example, when you spin on an office chair while repeatedly fixating on a point in your environment that disappears out of view due to your movement.

Question 10

Whats electrooculography?

Answer 10

A recording where electrodes are place on the skin near the eyes and the eye movements are recorded.

Question 11

What’s Saccadic Masking?

Answer 11

When the eye moves from one object to another, the image will be blurred. Although an observer will see your eyes movements yourself will not

Question 12

What is the anatomical basis of the blind spot?

Answer 12

It is that there are no photoreceptors in that certain area of the retina

Question 13

What happens when you mechanically stimulate your retina?

Answer 13

Mechanical stimulation of the eye causes random firing of the cells in the retina that is similar to when light stimulated the retina. This is a type of entopic phenomenon (visual effects produced by the eye itself). also known as phosphene

Question 14

What is suggested about the response time of photoreceptors to light?

Answer 14

Photoreceptors have a fast and slow response to light

Question 15

Why do you suppose you are not able to see blood vessels in the retina normally?

Answer 15

Because the brain suppresses the image of the retinal blood vessels

Question 16

Why is it that when spinning around, after some time you don’t feel like you are spinning, and once you stop you feel like you’re spinning in the opposite direction?

Answer 16

The reason lies with how the semicircular canals detect acceleration. This is because of the semicircular canal fluids move independently from the cupula (contains sensory cells’ cilia).