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Neuroscience & Mental Health Y2 > Structure and Function of the Eye > Flashcards

Structure and Function of the Eye Flashcards

1
Q

Where does the eye sit

A

Orbit

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2
Q

The sclera is…

A

the white part of the eye

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3
Q

medial canthus is…

A

medial corner of the eye

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4
Q

The lateral canthus is…

A

lateral corner of the eye

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5
Q

The palpebral fissure is…

A

where the upper eyelet bends back

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6
Q

The limbus is…

A

the border between the cornea and sclera

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7
Q

the border between the cornea and sclera is known as…

A

the limbus

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8
Q

where the upper eyelid bends back is known as…

A

palpebral fissure

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9
Q

the white part of the eye is known as…

A

sclera

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10
Q

the corners of the eye is known as…

A

canthus

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11
Q

the pink bit near the medial canthus is known as…

A

caruncle

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12
Q

The caruncle is …

A

the pink bit near the medial canthus

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13
Q

Why is the pupil black

A

black because the inside of the eye is coated in pigment epithelium which doesn’t allow light to escape

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14
Q

What are basal tears

A

tears produced to keep the cornea wet

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15
Q

The three types of tears the cornea produces?

A

Basal, reflex and crying tears

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16
Q

Afferent and efferent nerves, and NT of the tear production reflex

A

ACh, afferent - ophthalmic branch of the trigeminal

Efferent- Parasympathetic

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17
Q
  • Tear produced by …
A

lacrimal gland

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18
Q
  • Tear drains through …
A

the two puncta, opening on medial lid margin

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19
Q

What are the puncta

A

hole where tears drain through

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20
Q
  • Tear flows through the … (2)
A

superior and inferior canaliculi

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21
Q
  • Tears gather in the…
A

tear sac

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22
Q

Tearsexits the tear sac through the XX and into XX

A

through the tear duct into the nose cavity

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23
Q

Describe the route tears take from production to drainage (5)

A
  • Tear produced by lacrimal gland
  • Tear drains through the two puncta, opening on medial lid margin
  • Tear flows through the superior and inferior canaliculi
  • Tear gathers in tear sac
  • Tears exits the tear sac through the tear duct into the nose cavity
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24
Q

Purposes of the tear film? (4)

A
  • Tear film maintains smooth cornea-air surface
  • Oxygen supply to cornea- normal cornea has no blood vessels
  • Removal of debris (tear film & blinking)
  • Bactericide
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25
Q

Blood supply to the cornea?

A

There is none physiologically

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26
Q

Three layers of the tear film?

A

Superficial oily layer
Aqueous tear film
Mucinous layer

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27
Q

Purpose of the Mucinous layer in tear film

A

on the corneal surface to maintain surface wetting

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28
Q

Purpose of the Superficial oily layer in tear film

A

to reduce tear film evaporation (produced by a row of Meibomian glands along the lid margins)

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29
Q

What produces the Superficial oily layer in tear film and where are these cells found

A

Meibomian glands along the lid margins

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30
Q

What is the CONJUNCTIVA

A

The thin, transparent tissue that covers the outer surface of the eye

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31
Q

What is the cornea

A

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber

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32
Q

Nourishment of the cornea is through…

A

tiny blood vessels that are nearly invisible to the naked eye

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33
Q

The conjunctiva begins where and lines what

A

begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids

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34
Q

Retina is made of..

A

nerve tissue

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35
Q

Where is the uvea and what does it consist of (3)

A

around the retina- it consists of the iris, ciliary body and choroid

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36
Q

What is the choroid and its purpose?

A

a spongey vessel structure that nourishes the retina

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37
Q

what is the sclera made of and its function

A

collagen structure that protects the eye posterior

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38
Q

From out to in, order the sclera, choroid and retina

A

sclera, choroid, retina

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39
Q

purpose of the Cornea

A

protects eye anteriorly

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40
Q

Choroid colour and function

A

Pigmented and vascular

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41
Q

refractive index of cornea vs air

A

higher refractive index than air

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42
Q

Water content of the cornea and why is not as such

A
  • Low water content Dehydrated by corneal endothelium in order to remain transparent
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43
Q

Cornea is continuous with X layer

A

scleral

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44
Q

5 layers of the cornea?

A
  1. EPITHELIUM
  2. BOWMAN’S MEMBRANE
  3. STROMA
  4. DESCEMET’S MEMBRANE
  5. ENDOTHELIUM
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45
Q

2 names membranes in the cornea? which layer of the cornea are they?

A

2 - Bowmans is outer

4 - Descemet in inner

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46
Q

Endothelial cell dysfunction may result in … (2)

A

corneal oedema and corneal cloudiness

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47
Q

3 parts of the uvea?

A
  1. Iris
  2. Ciliary body
  3. Choroid
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48
Q

photoreceptors in retina are cells that transforms X into Y

A

photons into electrons

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49
Q

Choroid is between …

A
  • Between retina and sclera
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50
Q

choroid is mainly composed of …

A

posed of layers of blood vessels that nourish the back of the eye

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51
Q

Choroid vessels nourish what part of the eye

A

posed of layers of blood vessels that nourish the back of the eye

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52
Q

What is the loss of transparency in the lens known as

A

cataracts

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53
Q

Three functions of the lens?

A
  • Transparency
  • Refractive power
  • Accommodation
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54
Q

Lens is suspended by a fibrous rings known as…

A

lens zonulae

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55
Q

lens zonulae are …

A

fibrous rings suspending the lens

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56
Q

When the muscle constricts, the pressure on the zonula is X so the lens gets smaller and thicker

A

released

57
Q

Optic nerve connects to the eye near the X

A

macula

58
Q

Visible portion of the optic nerve is known as…

A

Optic disc

59
Q

MACULA is located roughly …

A

In the centre of the retina

60
Q

MACULA is slightly [temporal/nasal] to the X

A

temporal

optic nerve

61
Q
  • The fovea is the …
A

very centre of the macula

62
Q

What divides the eye into the anterior and posterior segments

A

lens

63
Q

the anterior chamber is between the….

A

cornea and the lens

64
Q

the anterior chamber is filled with….

A

aqueous humour

65
Q

What secretes aqueous humour

A

ciliary body

66
Q

ciliary body is responsible for …

A

secreting aqueous humour

67
Q

X drains the fluid out of the eye

A

trabecular meshwork

68
Q

What does the trabecular meshwork do

A

drains the fluid out of the eye

69
Q

Purpose of the aqueous humour?

A

Provide nutrients to the eye

70
Q

Describe the flow of the aqueous humour starting with entering the anterior chamber and its 2 methods of exit

A
  • Enters anterior chamber and is then reabsorbed by Trabecular meshwork (then can escape meshwork via Canal of Schlemm that will push aqueous humour into the venous stream (80-90%), OR can escape passively via passive flow inside the uvea and sclera (uveal-scleral flow= 10-20%))
71
Q

Prostaglandins to treat glaucoma work how

A

increase uveal-scleral flow

72
Q

What is glaucoma

A

MEDICAL CONDITION OF SUSTAINED RAISED INTRAOCULAR PRESSURE

73
Q

What does glaucoma result in (2 things and this causes 2 things)

A
  • Retinal Ganglion cell death and enlarged optic disk cupping
  • Visual field loss, blindness
74
Q

2 types of glaucoma?

A

PRIMARY OPEN ANGLE GLAUCOMA

CLOSED ANGLE GLAUCOMA

75
Q

Which is the most common type of glaucoma

A

PRIMARY OPEN ANGLE

76
Q

What is at fault in PRIMARY OPEN ANGLE glaucoma

A

Trabecular meshwork dysfunction

77
Q

What happens in closed ANGLE glaucoma

A

Increased pressure pushing iris/lens complex forwards, blocking trabecular meshwork- vicious cycle

78
Q

risk factors for closed angle glaucoma (2)

A

small eye (hypermetropia), narrow angle at trabecular meshwork

79
Q

Presentation of glaucoma (2)

A

sudden painful red eye with acute drop in vision

80
Q

surgical treatment for glaucoma ?

A

peripheral laser iridotomy to create a drainage hole on the iris

81
Q

Why is there a blind spot in the eye and where is it

A
  • Where the optic nerve meets the retina there are no light sensitive cells
82
Q

concentration of rods and cones in the fovea?

A

highest concentration of cones, but a low concentration of rods

83
Q
  • Loss of foveal vision results in what acuity
A

poor visual acuity

84
Q

2 categories of visual function?

A

Central and peripheral

85
Q

how to assess central vision?

A

visual acuity assessment

86
Q

how to assess peripheral vision?

A

visual field assessment

87
Q

Loss of peripheral vision manfests as….

A

unable to navigate environment, patient may need white stick even with perfect acuity

88
Q

what nerves are in the outer layer of the retina and what do they do

A

Photoreceptors (1st order neurons)- detection of light

89
Q

what nerves are in the middle layer of the retina and what do they do

A

 Bipolar cells (2nd order neurons)- Local sign processing to improve contrast sensitivity, regulate sensitivity

90
Q

what nerves are in the inner layer of the retina and what do they do

A

Retinal ganglion cells (3rd order neurons)- Transmission of signal from the eye to the brain

91
Q

What is the fovea

A

pit at the centre of the macula due to absence of overlying ganglion cell layer

92
Q

What causes the pitting of the fovea

A

pit at the centre of the macula due to absence of overlying ganglion cell layer

93
Q

Where is the highest concentration of photoreceptors

A
  • Fovea
94
Q

Physical difference between rod and cone cells?

A
  • Longer outer segment in rod cells
95
Q

difference in light sensitivity between rod and cone cells?

A
  • rods 100x more sensitive to light than cones
96
Q

difference in speed of response to light between rod and cone cells?

A

rods are Slower in response to light

cones are faster

97
Q

difference abundance of rod and cone cells

A

120m rods

6m cones

98
Q

What cells are responsible for night vision

A

rods

99
Q

What cells are responsible for day vision

A

cones

100
Q

What cells are responsible for colour vision

A

cones

101
Q

What is day light colour vision known as

A

Phototopic

102
Q

What is nightvision known as

A

scotopic

103
Q

Map out the distribution of cone and rod cells (like it would look on a chart)

A

DO it

104
Q

S-cones - wavelength and colour

A

short wavelength = blue

105
Q

M-cones - wavelength and colour

A

medium wavelength = green

106
Q

L-cones - wavelength and colour

A

long wavelength = red

107
Q

rod wavelengths that are detected between X and Y cones

A

M and S

108
Q

Deuteranomaly …

A

the most common colour vision deficiency as involves not being able to see red well

109
Q

Example of a colour perception test?

A

ISHIHARA TEST

110
Q

What colour vision does the Ishihara test test?

A

red green deficiencies only

111
Q

Speed of cone dark adaptation?

A

7 minutes

112
Q

Speed of rod dark adaptation?

A

30 minutes

113
Q

Why is the Speed of rod dark adaptation fairly long

A

it has to regenerate rhodopsin

114
Q

how long does full light adaptation take

A
  • Occurs over 5 minutes
115
Q

what happens to rod/cone function in the light adaptation?

A

inhibited

116
Q

what mediums does light have to travel through (6)

A

light has to go through tear film, cornea, aqueous humour, lens, vitreous humour and the retina

117
Q

What is EMMETROPIA

A

Adequate correlation between axial length and refractive power
- Parallel light falls on to the retina- no accommodation

NO PROLEM

118
Q

What is AMMETROPIA

A

Mismatch between axial length and refractive power

- Parallel light rays don’t fall on the retina- no accommodation

119
Q

What is MYOPIA

A

Parallel rays converge at a focal point anterior to the retina

  • Near sightedness
120
Q

What is HYPEROPIA

A

Parallel rays converge at a focal point posterior to the retina

  • Far sightedness
121
Q

What is AMBLYOPIA

A

uncorrected hyperopia >5D, difference between 2 eyes whereby one eye is very hyperopic- the brain begins to ignore the hyperopic eye

122
Q

What is ASTIGMATISM

A

Parallel rays come to focus in 2 focal lines rather than a single focal point

123
Q

What is PRESBYOPIA

A

Naturally occurring loss of accommodation (focus on near objects

124
Q

Aetiology of MYOPIA

A

Unclear, genetic factor

125
Q

Aetiology of ASTIGMATISM

A

Hereditary

126
Q

Aetiology of HYPEROPIA

A

Unclear, inherited

127
Q

Physical cause of myopia? (2)

A

Excessive long globe (axial myopia) (more common)

Excessive refractive power (refractive myopia)

128
Q

Physical cause of hyperopia?

A

Excessive short globe (axial hyperopia) (more common)

Insufficient refractive power (refractive hyperopia)

129
Q

Physical cause of astigmatism?

A

Refractive media is not spherical  Refracts differently along one meridian than along meridian perpendicular to it  2 focal points (punctiform (dot-like) object is represented as 2 sharply defined lines)

130
Q
  • Asthenopic symptoms of hyperopia? (4)
A

 Eye pain
 Headache in frontal region
 Burning sensation in eyes
 Blepharoconjunctivitis

131
Q

What is near vision adaptation

A

Pupillary mitosis by the sphincter pupillae to increase depth of field
Convergence by the medial recti to a near object
Accommodation by the circular ciliary muscle to increase the refractive power of the lens for near vision

132
Q

5 options for optical correction?

A 
SPECTACLE LENSES
CONTACT LENSES
INTRAOCULAR LENSES
SURGICAL CORRECTION
CLEAR LENS EXTRACTION + IO
133
Q

Accommodation mechanism via the circular muscle? What nerve mediates this?

A

The lens is suspended by a ring of zonules and is anchored to the ciliary body. When the circular ciliary muscle within the ciliary body contracts, it pushes the inner edge of the ciliary body towards the lens and relaxes the passive zonules. This allows the lens to return to its natural thicker curved configuration, thus increasing its refractive power.
This process is mediated by the efferent CN III.

134
Q

A sty is infection of the …

A

Meibomian glands

135
Q

What layer of the eye goes red during infection/inflammation

A

Conjunctiva

136
Q

The posterior chamber is filled with …

A

vitreous humour

137
Q

The function of the corneal endothelium is to…

A

o Pumps fluid out of the cornea and prevents corneal oedema

138
Q

Why is injury or disease of the corneal endothelium quite serious

A

There is no regenerative power in it

139
Q

2 layers of the iris and what they’re composed of?

A

2 layers: a THIN POSTERIOR pigmented epithelial layer and a THICK ANTERIOR layer composed of stromal tissue and smooth muscles

Neuroscience & Mental Health Y2 (18 decks)

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