Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Nervous System > Sensory Systems - Ophthalmology - How We See > Flashcards

Sensory Systems - Ophthalmology - How We See Flashcards

1
Q

what is refraction?

A

Bending of light when it passes from one optical medium to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is accomodation?

A

We can focus on far off or near objects by changing how much we bend the light rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what leads to refractory errors

A

Sometimes there is a mismatch between how much we bend light rays leading to

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a bioconvex lens?

A

Biconvex lens is a simple lens which comprises two convex surfaces in spherical form, generally having the same kind of radius of curvature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is a bioconcave lens?

A

Bi-concave lenses have two inward curved surfaces. These lenses have a negative focal length.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is found in the fibrous coat of the eyeball?

A

cornea, sclaera, aqueous humor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is found in the vascular coat?

A

iris, ciliary body, choroid (aqueous humour)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is found in the sensory coat of the eye?

A

retina, vitreous humor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does a sharp image form on the retina?

A

Light waves from an object bend at the cornea, bend some more at the lens to form a clear image on the retina. This bending of light waves is called Refraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the two media of the eye responsible for the bending of light?

A

cornea and the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

which of the cornea and lens is more powerful at bending light?

A

Cornea is the most powerful “bender” of light (45D) but lens (15D) has the capacity to change its “bending power”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

when objects are distant >6 metres which rays reach the eye?

A

When objects are distant (>6m) then only parallel rays from the object reach the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

when objects are up close which rays reach the eye?

A

But when objects are up close divergent rays from the object reach the eye. They need to be “bent” more to bring them to a focus on the retina - in order to do this, the lens becomes thicker, which is something that forms part of accommodation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does a sharp image form on the retina?

A

When an object comes closer, the eye needs more bending power to focus on an object🡪 The lens becomes thicker & hence more powerful, and a clear image is formed on the retina again.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is accomodation?

A

Our eyes have the capacity to change focus from distant objects (infinity) to close objects (20cm).
The changes occurring in both eyes as it changes focus from a distant to a close object is called as accommodation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

3 things happen simultaneously & comprise accommodation, what are they?

A

Lens changes shape (becomes thicker & more spherical)
Pupil constricts
Eyes converge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the process of making the lense thicker (4)?

A

Ciliary muscle contracts making the ciliary body bulge
Space in the middle decreases
Suspensory ligaments become lax
Lens is no longer under stretch
LENS BECOMES THICKER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what causes the ciliary muscle to contract?

A

Ciliary body contraction (parasympathetic) causes lens to become thicker & more spherical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what causes the pupil to constrict?

A

Pupillary constrictor (sphincter pupillae) is a concentric muscle around the border of the pupil which gets parasympathetic innervation from CN3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when does the pupil need to constrict?

A

When we are looking at an object up close, we need a sharp focus.
To sharpen focus the pupil constricts to allow only a few rays (those from the object) to pass through.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

when are your eyes required to converge?

A

When focussing on an object up close, our eyes have to turn in to look at the object🡪 convergence.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

which muscles are used to converge the eye?

A

We use our medial rectus muscles of both eyes to converge.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the medial rectus muscles both innervated by?

A

Cranial nerve 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

which muscles are thicker medial recti muscles or lateral recti muscles?

A

Humans spend a lot of time doing ‘close’ work, so our Medial recti muscles are thicker than our lateral recti muscles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is myopia?

A

short-sightedness

rays are focused infront of the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is hyperopia?

A

long-sightedness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is astigmatism?

A

non-spherical curvature of cornea (or lens)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is presbyopia?

A

long-sightedness of old age

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is emmetrope?

A

perfect vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how do objects appear in myopia?

A

Close objects look clear, distant objects appear hazy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is the most common cause of myopia?

A

eyeball too long

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is the pathophysiology of myopia?

A

eyeball too long
So when the cornea + lens bend rays of light, they make the image form IN FRONT OF the retina. So far off objects not seen clearly.
(Basically the “bending power” of cornea + lens is too much for that eyeball)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what happens in myopia when an object is brought closer?

A

When the object is brought closer, divergent rays from the object reach the cornea; and then this “bending power” comes to use. The image is formed on the retina without needing to increase curvature of lens (i.e. without using the accommodative power.
Can see near things clearly i.e. near-sighted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what are symptoms of myopia?

A

Headaches, Complain of not being able to see blackboard/ distant objects.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is often seen in infants and preverbal children with myopia?

A

divergent squint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is often seen in toddlers with myopia?

A

loss of interest in sports/people. More interest in books, pictures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

how urgently must a divergent squint be dealt with?

A

deal with that aggressively if you’re not to make one of the eyes lose their vision or make it a lazy eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what is the treatment for myopia?

A

Bending power needs to be decreased.
Biconcave lenses

  • spectacles
  • contact lenses
  • laser eye surgery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

when is laser eye surgery of greatest benefit?

A

this procedure is of greatest benefit when you have a steady power,
which means that your power doesn’t change any more as you grow or you have a higher power
something like minus four, minus five and beyond, where you cannot manage without glasses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

how do objects appear in hyperopia?

A

Close objects look hazy, distant objects appear clear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

how does an emmetrope use accomodative power?

A

If you’re an emmetrope and you’re looking at somebody far away,

you should be able to see them without using your accommodative power.

But this person here is sitting within that six metre distance. So in order to see him, you are going to start using up your accommodative power.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

how would a hypermetrope use accomodative power?

A

a hypermetrope now has to use their accommodative power in order to be able to see all these people far away.

And so people far away are quite clear. You can see them because you’re using your accommodative power.But by the time you’ve come to six metres, while an emmetrope would have started using their accommodative power to start seeing them,

a hypermetrope has no more accommodative power at their disposal and therefore near objects appear quite hazy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is the cause of hyperopia?

A

Eyeball too short or cornea + lens too flat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

explain the pathophysiology of hyperopia?

A

Eyeball too short or cornea + lens too flat.
So the image of a distant object is formed BEHIND THE RETINA.

The person then automatically starts to use his accommodative power and makes the lens thicker. This causes the image to form on the retina.
So he is using his lens power to see far off things (that he should normally be seeing without using any power).
When seeing closer objects, he uses more and more power until ultimately, his power is all used up!
So he can’t see nearby objects ie. “longsighted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what are symptoms of hyperopia in a young individual?

A

eyestrain after reading/ working on the computer in a young individual.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what are symptoms of hyperopia in a child/toddler?

A

Convergent squint in children/ toddlers – needs immediate correction with glasses/lenses to preserve vision in both eyes and prevent a “lazy eye”.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what is the treatment for hyperopia?

A

Biconvex glasses alleviates use of glasses for focussing distant objects and ‘rests’ the accomodative power
Contact lenses
Laser Eye surgery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

how do objects appear in astigmatism?

A

Close and distant objects appear hazy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is the pathophysiology of astigmatism?

A

cornea is shaped more like a rugby ball than a football

So the bending of light rays along one axis will never be the same as that of the other axis.

So image formed is always hazy, whatever the distance of the object.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is the treatment for astigmatism?

A

So to correct it we need special glasses – called cylindrical glasses (which are curved in only one axis).

Laser eye surgery can also be used to correct the defect.

Need special contact lenses called toric lenses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what is the pathophysiology of presbyopia?

A

With age the lens gets less mobile/elastic.
So when the ciliary muscle contracts, it is not as capable as before to change shape.
So seeing near objects/ reading the newspaper starts to become difficult🡪 needs glasses to read.
Usually starts in 5th decade of life.

51
Q

how is presbyopia corrected?

A

Correction is by using biconvex “reading glasses”

52
Q

in a prescription note what does BC stand for?

A

base curvature and it is telling you how curved your cornea is so that the contact lens can be shaped to your cornea

53
Q

in a prescription note what does DIA stand for

A

DIA shows you the diameter of the cornea so you can make your contact lenses as big as that to cover the entire cornea

54
Q

In a prescription what does CYL stand for?

A

power required to correct astigmatism

55
Q

In a prescription what does the axis represent?

A

number between 1-180 showing the degree at which the astigmatism lies

56
Q

what is visible light a form of?

A

electromagnetic wave

57
Q

what do the energy in light waves need to stimulate?

A

photoreceptor cells on the retina (phototransduction)

58
Q

what is phototransduction defined as?

A

Phototransduction is defined as the conversion of light energy to an electrochemical response by the photoreceptors (rods and cones)

59
Q

what do the phototransduced roads and cones need to do?

A

need to activate optic nerve cells (generate an action potential)

60
Q

label the different features of road & cone?

A
61
Q

what does this image show?

A
62
Q

what is each lamellae made up of?

A

Each lamellae is made up of cell membrane. Integrated into this cell membrane is the visual pigment rhodopsin in rods and cone opsins S, M and L in cones. These molecules differ in their spectral sensitivity

63
Q

label this diagram?

A
64
Q

chromophore nests in the opsin what is this molecule formed from?

A

dietary vitamin A

65
Q

what happens when light falls of 11-cis retinal?

A

it isomerises to all-trans retinal

66
Q

what is an issue with all-trans retinal?

A

cannot fit into the opsin. So rhodopsin splits. This results in BLEACHING of the visual purple

67
Q

describe what is shown in the image?

A

So if you think of this as the retina and it normally looks this reddish colour.

When light falls on it and the 11-cis retinal has become all-trans retinal and therefore moves away from the opsin,

you find this bleaching until you have a bleached compound.

68
Q

describe what is shown in the image?

A

So if you think of this as the retina and it normally looks this reddish colour.

When light falls on it and the 11-cis retinal has become all-trans retinal and therefore moves away from the opsin,

you find this bleaching until you have a bleached compound.

69
Q

How does bleaching of the visual pigment result in phototransduction?

A

Phototransduction cascade.

70
Q

What role does Vitamin A play in the visual pigment?

A

visual pigment regeneration

71
Q

study the phototransduction cascade?

A
72
Q

study visual pigment regeneration?

A
73
Q

what symptoms will someone suffereing with vitamin A deficiency present with?

A

supplied through the diet, any condition that affects vitamin A absorption will affect vision – (night)blindness. Vitamin A is also essential for healthy epithelium. So conjunctiva and corneal epithelium are also abnormal.

74
Q

what conditions might vitamin A deficiency present in?

A

conditions such as malnutrition, malabsorption syndromes such as coeliac disease, sprue.

75
Q

what are characteristic features of vitamin A deficiency that may be seen in the eyes?

A

Bitot’s spots in conjunctiva are sometimes the first indication of Vitamin A deficiency

Corneal ulceration ( green colour is dye to show up extent of ulcer)

corneal melting
Which leads to future opacification of the cornea

76
Q

what is the role of intrinsic occular muscles?

A

control pupil diameter & helps alter lens curvature to enable us to see near objects

77
Q

what is the role of extrinsic occular muscles?

A

move the eye.

78
Q

what are the six extrinsic occular muscles of the eye?

A

4 Straight muscles called recti
Medial rectus (MR)
Lateral rectus (LR)
Inferior rectus (IR)
Superior rectus (SR)

2 oblique muscles
Superior Oblique (SO)
Inferior Oblique (IO)

79
Q

what are the four straight extrinsic occular muscles of the eye?

A

medial rectus (MR)
Lateral rectus (LR)
Inferior rectus (IR)
Superior rectus (SR)

80
Q

what are the 2 oblique extrinsic muscles of the eye?

A

2 oblique muscles
Superior Oblique (SO)
Inferior Oblique (IO)

81
Q

where do the recti muscles of the eye arise from?

A

The recti muscles arise from the apex of the orbit from an annular fibrous ring

82
Q

where do the superior oblique muscles arise from?

A

The superior oblique muscle arises from the roof of the orbit posteriorly

83
Q

where do the inferior oblique muscles arise from?

A

The inferior oblique muscle arises from the floor of the orbit anteriorly

84
Q

what lies just above the superior rectis?

A

the LPS (levator palpebrae superioris) is a muscle running to the upper eyelid to elevate it

85
Q

how do the recti muscles insert into the sclera versus the obliques?

A

The recti muscles insert onto sclera anteriorly
Obliques insert posteriorly

86
Q

what is the origin and insertion of the L.P.S?

A

origin - roof of orbit
insertion - upper eyelid

87
Q

what is the origin and insertion of all recti?

A

origin - tendinous ring
insertion - sclera anteriorly

88
Q

what is the origin and insertion of the superior oblique?

A

origin - lesser wing of sphenoid
insertion - sclera posteriorly

89
Q

what is the origin and insertion of inferior oblique?

A

orgin - medial part of orbit floor
insertion - sclera posteriorly

90
Q

what does the trochlear (IV) nerve supply?

A

supplies muscle with trochlea (SO)

91
Q

what does the abducent nerve (VI) supply?

A

supplies muscle which abducts (LR)

92
Q

what nerve is the rest of the eye supplied by?

A

Everything else – Oculomotor (III) nerve

93
Q

uniocular?

A

located/confined to one eye

94
Q

binocular?

A

both eyes

95
Q

what is intorsion?

A

when the top of the eyeball rotates towards the nose

96
Q

what is extorsion?

A

when the top of the eyeball rotates away from the nose

97
Q

what is the primary action of the medial rectus?

A

adduction

98
Q

what is the primary action of the lateral rectus?

A

abduction

99
Q

what is the primary action of the superior rectus?

A

Elevation
Adduction
Intorsion

100
Q

what is the primary action of the inferior rectus?

A

depression
adduction
extorsion

101
Q

what is the primary action of the superior oblique?

A

Intorsion
depression
abduction

102
Q

what is the primary action of the inferior oblique?

A

extorsion
elevation
abduction

103
Q

what are the action of EOM influences by?

A

The muscles are attached along the orbital axis and not the optical axis, so they pull on the eyeball at an angle. This is a muscle has more than one action

The Oblique muscles are attached to the posterior part of the sclera, so they pull the posterior part of the eyeball up/down & the anterior part moves in the opposite direction

104
Q

label the nerve and muscle associated with each movement?

A
105
Q

what do obliques do when eye is adducted?

A

elevate/ depress when the eye is adducted

106
Q

what do recti do when eye is abducted?

A

elevate/depress when the eye is abducted.

107
Q

what is strabismus?

A

Misalignment of the eyes
Esotropia (manifest convergent squint)
Exotropia (manifest divergent squint)

108
Q

what are functional consequences of a squint?

A

amblyopia
diplopia

109
Q

what is amblyopia?

A

(lazy eye) where brain supresses the image of one eye leading to poor vision in that eye without any pathology (correctable in early years using eye patches to stimulate the “lazy” eye to work)

110
Q

what is diplopia?

A

(double vision) – usually occurs in squints occuring as a result of nerve palsies.

111
Q

what are the instrinsic eye muscles?

A

Ciliaris muscle in ciliary body
Constrictor pupillae in iris at pupillary border
Dilator pupillae radially running muscle in iris

112
Q

what innervates both cillaris muscle and constrictor pupillae?

A

1 and 2 innervated by parasympathetic (IIIn)

113
Q

what innervated dilator pupillae?

A

3 by sympathetic (from plexus around blood vessels)

114
Q

what does pathology of innervation of intrinsic muscles leads to?

A

pupillary abnormalities

115
Q

what is the pupillary responce to increased illumination?

A

increased illumination🡪 parasympathetic🡪 both pupils constrict

116
Q

what is the puppilary response to decreased illumination?

A

Decreased illumination🡪 sympathetic🡪 pupils dilate

117
Q

how do you elicit the pupillary reflex?

A

location - dimly lit room

Pen torch in front of one eye 🡪 check for both pupils constricting (Direct and consensual reflex)

Swing light to other side 🡪 should remain both pupils constricted

118
Q

describe the pathway of light reflex in the afferent limb?

A
119
Q

describe the pathway of light reflex in the efferent limb?

A
120
Q

what are some pupil abnormalities?

A

Pupils maybe of different sizes – anisocoria eg: Horner’s syndrome
Pupils may look normal but react abnormally to light (abnormal light reflex)

121
Q

what are some common causes of absent/abnormal pupillary reflex?

A

Diseases of the retina – detachment/ degenerations or dystrophies
Diseases of the optic nerve – such as in optic neuritis (frequently seen in MS)
Diseases of the III cranial nerve (efferent limb)

122
Q

3rd nerve cranial palsy?

A

In III n palsy due to a medical cause such as diabetes, there is usually no damage to parasympathetic fibres. So if you see a patient with a IIIn palsy, check pupillary
reflex🡪 if absent🡪 suspect a cerebral artery aneurysm 🡪emergency

123
Q

what is horners syndrome?

A

Anisocoria due to damage to the sympathetic innervation to the pupil.
You might also see ptosis (drooping of the eyelid) on the affected side
Other signs – anhidrosis (loss of sweating on the affected side)

124
Q

sympathetic innervation of the eye?

A

remember the thoracolumbar outflow of the sympathetic
Remember the sympathetic chain and cervical ganglia
Remember that in the head and neck – postganglionic sympathetic fibres travel along with blood vessels

Nervous System (40 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions