The Concept of Vision

Question 1

Describe the rays of light which hit the eye when looking at far away objects?

Answer 1

Only parallel rays hit the cornea. No light bending is required and field of vision is infinite

Question 2

What happens when looking at objects up close?

Answer 2

Divergent rays hit the cornea and the lens needs to bend the rays to form an image

Question 3

Explain Accommodation?

Answer 3

The ability to focus far away as well as up close

Question 4

What occurs when the ciliary muscle contracts?

Answer 4

The lens bulges and the space in the middle decreases

Question 5

What happens when the suspensory ligament relaxes?

Answer 5

Pressure on the lens decreases and it becomes more spherical which allows for focusing close up

Question 6

Lens thickening allows for what action?

Answer 6

Focusing on objects up close

Question 7

Parasympathetic action on the lens by which nerve permits the action of lens thickening?

Answer 7

The occularmotor nerve (CNIII)

Question 8

Name the three steps of accommodation?

Answer 8

1 Lens thickens 2. Pupil Constricts 3. Eyes converge

Question 9

What role does the pupil play in accommodation?

Answer 9

It constricts to allow only a few rays through, allowing for sharper focus

Question 10

What occurs in the convergence step of accommodation?

Answer 10

The eyes turn to look at the object by using the medial rectus

Question 11

What is myopia?

Answer 11

farsightedness. Occurs because eyeball is slightly longer so the image will form slightly in front of the retina. Far away = hazy

Question 12

What is hyperopia?

Answer 12

nearsightedness. Occurs because eyeball is too short or the cornea and lens is too flat. Near = hazy

Question 13

What is astigmatism?

Answer 13

Close and distant objects = hazy as surface has different curvatures in different meridians

Question 14

What causes presbyopia?

Answer 14

Lens is less stretchy

Question 15

What happens when the right optic nerve is damaged?

Answer 15

Blindness in one eye,

Question 16

What happens when the optic chiasma is disrupted in the middle?

Answer 16

bitemporal hemianopia

Question 17

What is refraction?

Answer 17

The bending of light to form a clear image on the retina

Question 18

When does the lens thicken?

Answer 18

As objects become closer to increase refraction

Question 19

How does the lens thicken?

Answer 19

Ciliary muscle contracts to make ciliary body bulge, space in middle decreases, suspensory ligaments relax and lens is no longer under stretch so lens can thicken

Question 20

What muscle is used for convergence?

Answer 20

Medial rectus

Question 21

Which rectus muscle is thicker in the eyes of humans?

Answer 21

The medial rectus

Question 22

Define presbyopia

Answer 22

Long sightedness of old age

Question 23

What is perfect vision also known as?

Answer 23

Emmetropia

Question 24

What are symptoms of myopia?

Answer 24

Headaches, unable to see distant objects, divergent squint

Question 25

How is myopia corrected?

Answer 25

Biconcave lenses

Question 26

What are symptoms of hyperopia?

Answer 26

Symptoms of eyestrain, convergent squint

Question 27

How is hyperopia corrected?

Answer 27

Biconvex lenses

Question 28

How is an astigmatism corrected?

Answer 28

Toric lenses or laser eye surgery

Question 29

What is phototransduction?

Answer 29

The conversion of light energy to an electrochemical response by rods and cones

Question 30

What do rods and cones activate?

Answer 30

Optic nerve neurones

Question 31

How does bleaching of the visual pigment result in phototransduction?

Answer 31

Phototransduction cascadde

Question 32

What role does Vit A play in visual pigment?

Answer 32

Visual pigment regeneration

Question 33

What does a vitamin A deficiency lead to?

Answer 33

night blindness and abnormal corneal epithelium or conjunctiva

Question 34

Where do medial fibres of the optic nerve cross over to the opposite side?

Answer 34

The optic chiasm

Question 35

Where do fibres of the optic tract synapse?

Answer 35

Lateral Geniculate Body of the Thalamus

Question 36

What happens if the right optic tract is damaged?

Answer 36

Contralateral Homonymous Hemianopia

Question 37

What happens if the optic radiation is damaged?

Answer 37

Contralateral homonymous hemianopia

Question 38

What do intrinsic muscles of the eye control?

Answer 38

Pupil diameter and lens curvature

Question 39

What do extrinsic muscles of the eye control?

Answer 39

Eye movement

Question 40

Where do the recti muscles arise from?

Answer 40

The apex of the orbit

Question 41

Where does the sup. oblique muscle arise from?

Answer 41

The roof of the orbit posteriorly

Question 42

Where does the inf. oblique arise from?

Answer 42

The roof of orbit anteriorly

Question 43

What is the function of the LPS?

Answer 43

to ELEVATE THE UPPER EYELID

Question 44

What do the obliques do when the eye is adducted?

Answer 44

Elevate/Depress the eye

Question 45

What do the recti do when the eye is abducted?

Answer 45

Elevate/Depress the eye

Question 46

What is the action of the MR?

Answer 46

Primary - ADDUCTION

Question 47

What is the action of the LR?

Answer 47

Primary - Abduction

Question 48

What is the action of the SR?

Answer 48

Primary - Elevation Secondary - Adduction Tertiary - Intorsion

Question 49

What is the action of the IR?

Answer 49

Primary - Depression Secondary - Adduction Tertiary - Extorsion

Question 50

What is the action of the SO?

Answer 50

Primary - Intorsion Secondary - Depression Tertiary - Abduction

Question 51

What is the action of the IO?

Answer 51

Primary - Extorsion Secondary - Elevation Tertiary - Abduction

Question 52

What is esotropia?

Answer 52

Convergent Squint

Question 53

What is extropia?

Answer 53

Divergent squint

Question 54

What are the consequences of having a squint?

Answer 54

Amblyopia - lazy eye Diploplia

Question 55

What are the ciliaris and constrictor pupillae innervated by?

Answer 55

Parasympathetically innervated by the CNIII

Question 56

Where is the ciliaris located?

Answer 56

Ciliary body

Question 57

Where is constrictor pupillae located?

Answer 57

in iris at pupillary border

Question 58

Where is dilator pupillae located?

Answer 58

Iris

Question 59

What occurs at times of increased illumiation?

Answer 59

Parasympathetic innervation causes pupils to constrict

Question 60

What occurs at times of decreased illumination?

Answer 60

Sympathetic innervation causes pupils to dilate

Question 61

Where do impulses of light travel once they fall on the retina?

Answer 61

Optic nerve -> optic chiasm -> optic tract --> midbrain

Question 62

Where do signals from light transduction go when the reach the EWN?

Answer 62

EWN --> preganglionic system in orbit --> ciliary ganglion --> constrictor pupillae