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Head, Neck and Eyes > The Concept of Vision > Flashcards

The Concept of Vision Flashcards

1
Q

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

A

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

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2
Q

What happens when looking at objects up close?

A

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

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3
Q

Explain Accommodation?

A

The ability to focus far away as well as up close

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4
Q

What occurs when the ciliary muscle contracts?

A

The lens bulges and the space in the middle decreases

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5
Q

What happens when the suspensory ligament relaxes?

A

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

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6
Q

Lens thickening allows for what action?

A

Focusing on objects up close

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7
Q

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

A

The occularmotor nerve (CNIII)

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8
Q

Name the three steps of accommodation?

A

1 Lens thickens 2. Pupil Constricts 3. Eyes converge

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9
Q

What role does the pupil play in accommodation?

A

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

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10
Q

What occurs in the convergence step of accommodation?

A

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

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11
Q

What is myopia?

A

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

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12
Q

What is hyperopia?

A

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

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13
Q

What is astigmatism?

A

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

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14
Q

What causes presbyopia?

A

Lens is less stretchy

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15
Q

What happens when the right optic nerve is damaged?

A

Blindness in one eye,

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16
Q

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

A

bitemporal hemianopia

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17
Q

What is refraction?

A

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

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18
Q

When does the lens thicken?

A

As objects become closer to increase refraction

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19
Q

How does the lens thicken?

A

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

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20
Q

What muscle is used for convergence?

A

Medial rectus

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21
Q

Which rectus muscle is thicker in the eyes of humans?

A

The medial rectus

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22
Q

Define presbyopia

A

Long sightedness of old age

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23
Q

What is perfect vision also known as?

A

Emmetropia

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24
Q

What are symptoms of myopia?

A

Headaches, unable to see distant objects, divergent squint

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25
Q

How is myopia corrected?

A

Biconcave lenses

26
Q

What are symptoms of hyperopia?

A

Symptoms of eyestrain, convergent squint

27
Q

How is hyperopia corrected?

A

Biconvex lenses

28
Q

How is an astigmatism corrected?

A

Toric lenses or laser eye surgery

29
Q

What is phototransduction?

A

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

30
Q

What do rods and cones activate?

A

Optic nerve neurones

31
Q

How does bleaching of the visual pigment result in phototransduction?

A

Phototransduction cascadde

32
Q

What role does Vit A play in visual pigment?

A

Visual pigment regeneration

33
Q

What does a vitamin A deficiency lead to?

A

night blindness and abnormal corneal epithelium or conjunctiva

34
Q

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

A

The optic chiasm

35
Q

Where do fibres of the optic tract synapse?

A

Lateral Geniculate Body of the Thalamus

36
Q

What happens if the right optic tract is damaged?

A

Contralateral Homonymous Hemianopia

37
Q

What happens if the optic radiation is damaged?

A

Contralateral homonymous hemianopia

38
Q

What do intrinsic muscles of the eye control?

A

Pupil diameter and lens curvature

39
Q

What do extrinsic muscles of the eye control?

A

Eye movement

40
Q

Where do the recti muscles arise from?

A

The apex of the orbit

41
Q

Where does the sup. oblique muscle arise from?

A

The roof of the orbit posteriorly

42
Q

Where does the inf. oblique arise from?

A

The roof of orbit anteriorly

43
Q

What is the function of the LPS?

A

to ELEVATE THE UPPER EYELID

44
Q

What do the obliques do when the eye is adducted?

A

Elevate/Depress the eye

45
Q

What do the recti do when the eye is abducted?

A

Elevate/Depress the eye

46
Q

What is the action of the MR?

A

Primary - ADDUCTION

47
Q

What is the action of the LR?

A

Primary - Abduction

48
Q

What is the action of the SR?

A

Primary - Elevation
Secondary - Adduction
Tertiary - Intorsion

49
Q

What is the action of the IR?

A

Primary - Depression
Secondary - Adduction
Tertiary - Extorsion

50
Q

What is the action of the SO?

A

Primary - Intorsion
Secondary - Depression
Tertiary - Abduction

51
Q

What is the action of the IO?

A

Primary - Extorsion
Secondary - Elevation
Tertiary - Abduction

52
Q

What is esotropia?

A

Convergent Squint

53
Q

What is extropia?

A

Divergent squint

54
Q

What are the consequences of having a squint?

A

Amblyopia - lazy eye

Diploplia

55
Q

What are the ciliaris and constrictor pupillae innervated by?

A

Parasympathetically innervated by the CNIII

56
Q

Where is the ciliaris located?

A

Ciliary body

57
Q

Where is constrictor pupillae located?

A

in iris at pupillary border

58
Q

Where is dilator pupillae located?

A

Iris

59
Q

What occurs at times of increased illumiation?

A

Parasympathetic innervation causes pupils to constrict

60
Q

What occurs at times of decreased illumination?

A

Sympathetic innervation causes pupils to dilate

61
Q

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

A

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

62
Q

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

A

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

Head, Neck and Eyes (14 decks)

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