Introduction

Question 1

State advantages of having two eyes?

Answer 1

1. Spare eye (insurance )
2. Increased sensitivity - two eyes/detectors are better than one , better able to detect visual stimuli = summation
3. Stereopsis - allows us to perceive depth 3D

Question 2

What is stereopsis ?

Answer 2

Ability to combine the images from two eyes - this gives one unified perception of the world

Question 3

Define ‘ Disparity ‘ .

Answer 3

Small hz differences between images in the two eyes that are still fusable

This difference is called disparity .

Question 4

Define ‘ Fusion ‘

Answer 4

Describes the neural processes that bring the retinal images in the two eyes to form/produce a single image.
Fusion occurs to allow BSV.

Question 5

State some conditions required for fusion to take place .

Answer 5

Images must be located on corresponding retinal areas and be relatively similar
Similar in SIZE , BRIGHTNESS, SHARPNESS

Question 6

What is sensory fusion ?

Answer 6

The neural combination of corresponding retinal images into a single Visual percept

Question 7

What is motor fusion ?

Answer 7

The ability to align the eyes in such a manner that sensory fusion can take place
Relies upon the proper functioning of the Intraocular muscles - to pt eye to look at similar object

Question 8

If you present dissimilar objects to both eyes what can occur ?

Answer 8

Suppression
Confusion
Rivalry

Question 9

Explain what ‘suppression’ is ?

Answer 9

Occurs to eliminate one image to prevent confusion

Question 10

What is ‘ confusion ‘?

Answer 10

Leads to one image on top of the other

Question 11

What is binocular rivalry ?

Answer 11

• When corresponding regions of the two eyes are stimulated by different patterns
• Stimuli rival in terms of our conscious visual perception and leads to confusion
• Stimulus seen at given point = DOMINANT
• Stimulas that can’t be seen = SUPPRESSED

Question 12

State the relationship between motor and sensory fusion?

Answer 12

If motor fusion breaks then sensory can’t take place

Question 13

Use the whiteboard to show the concept of corresponding retinal points .

Answer 13

Retinal location in RE and LE share a common visual direction
Normal

Question 14

Use the whiteboard to indicate disruption of the visual axis
Give any example.

Answer 14

Exotropia - right eye deviating outward
Both objects will compete for visual dominance
Corresponding points = confusion / rivalry
Non corresponding points = Diplopia

Question 15

Define ‘ Diplopia ‘

Answer 15

When non corresponding points are stimulated by the same object this causes diplopia.
This may occur as a result of misalignment of the visual axis

Question 16

What is another words for Diplopia ?

Answer 16

Double vision

Question 17

State the requirements for stereopsis

Answer 17

1) Binocular Overlap
2) Partial Decussation
3) Coordinated eye movement

Biological aspects

Question 18

What do we mean by binocular overlap ?

Answer 18

Monocular fields overlap

Question 19

What do we mean by partial decussation ?

Answer 19

Allows nueral signals from LE and RE to be combined

crossing of nasal fibres

Question 20

What do we mean by coordinated eye movements?

Answer 20

Gaze hold and Gaze shift

Question 21

Name the four types of eye movement

Answer 21

Saccadic
Pursuit
Vestibular reflexes
Vergences

Question 22

Define saccadic eye movement

Answer 22

Quick simultaneous movement of both eyes between 2 or more phases of fixation in same direction

Question 23

Define persuit eye movement

Answer 23

Eyes closely following a moving target

Question 24

Define vestibular reflex eye movement

Answer 24

Reflex acting to stabilise gaze during head movement with eye movement due to activation of vestibular system

Question 25

Define vergences in relation to eye movement

Answer 25

Slow movement of both eyes initiated to track and fuse moving objects located at different distances

Question 26

Use whiteboard to draw the extra ocular muscles in the eye

Answer 26

Recti muscles x4 | Oblique muscles x2

Question 27

What can go wrong with the binocular vision system ?

Answer 27

Misalignment of visual axis

Question 28

When there is a obvious observable misalignment of the visual axis What is this called ?

Answer 28

Manifest deviation

Question 29

When there is a non visible misalignment of the visual axis what is this called ? Explain ...

Answer 29

Latent deviation Can’t observe with naked eye , not visible Usually involves suspending fusion by covering eye

Question 30

Manifest deviation include ...

Answer 30

Strabismus Squint Heterotropias

Question 31

Latent deviation ...

Answer 31

Heterophorias

Question 32

Use the whiteboard to draw and name the types of manifest deviations

Answer 32

Exotropia Esotropia Hypertropia Hypotropia

Question 33

Name the two hz deviations in manifest deviations

Answer 33

Exo and esotropia

Question 34

Name the two vertical manifest deviations

Answer 34

Hyper and hypotropia

Question 35

Use the whiteboard to draw and name the latent deviations

Answer 35

Esophoria Exophoria Hyperphoria Hypophoria Have to cover one eye - cover test to reveal presence of deviation

Question 36

What method would you use to detect any ocular deviations ?

Answer 36

The cover test

Question 37

Epicanthic fold ...

Answer 37

Children may look like they have an esotropia but they don’t they just have an epicanthic fold which gives the impression

Question 38

Use the whiteboard to draw the classification system of BV abnormalities

Answer 38

Concomitant or incomitant