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Sem 3 > Case 3 > Flashcards

Case 3 Flashcards

1
Q

what is the fascial sheath of the eyeball?

A

Extends from the optic nerve to the corneoscleral junction, and separates the eye from periorbital fat

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2
Q

What is the medial check ligament?

A

Expansion of the fascial sheath of the medial rectus muscle, what prevents over-action of this muscle

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3
Q

What is the lateral check ligament?

A

Expansion of the fascial sheath of the lateral rectus muscle, what prevents over-action of this muscle

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4
Q

What is the name given to the space between the eyelids when they are open?

A

Palprebral fissure

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5
Q

What are the angles of the palprebral fissure called?

A

Medial and lateral commissure

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6
Q

Which is bigger, the medial or lateral commissure?

A

Medial

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7
Q

What is found in the medial commisure?

A

Lacrimal caruncle

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8
Q

What is the reddish elavation in the medial commissure that contains oil and sweat glands?

A

Larcrimal caruncle

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9
Q

What is found in the lacrimal caruncle?

A

Oil and sweat glands

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10
Q

What are the layers of the eyelid?

A

(1) Epidermis
(2) Dermis
(3) Subcutaneous tissue
(4) Obicularis Oculi fibres
(5) Tarsal plate
(6) Tarsal glands
(7) Conjunctiva

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11
Q

What are the two parts to the orbicularis oculi muscle?

A

Orbital part and palprebrae part

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12
Q

What innervates the orbicularis oculi muscle?

A

Facial nerve

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13
Q

What is the role of the orbucularis oculi muscle?

A

To close the eyelids

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14
Q

What ligaments anchor the palprebral part of the OO muscle?

A

Medial and lateral palprebral ligaments

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15
Q

What is the tarsal plate?

A

A thick fold of connective tissue

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16
Q

Which is bigger: superior or inferior tarsus?

A

superior tarsus

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17
Q

What muscle is the superior tarsus associated with?

A

Levator palprebrae muscle

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18
Q

What is the role of the levator palprebral muscle ? what innervates it?

A

Parasympathetic fibres of the oculomotor nerve.

I keeps the eyelid open.

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19
Q

Where does the levator palprebrae muscle extend from?

A

Lesser wing of sphenoid (to the superior tarsus muscle).

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20
Q

What type of glands are the tarsus glands?

A

sebacceous (oil) glands

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21
Q

What is another name given to the tarsus glands?

A

Meibomian glands

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22
Q

What does infection of a tarsal gland cause?

A

A cyst called a chalzion.

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23
Q

What is conjunctiva?

A

non-keratinised stratified columnar epithelium

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24
Q

What are the two types of conjunctiva?

A

Palprebral and bulbar

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25
Q

where is palprebral conjunctiva found?

A

On the inner aspects of eyelids

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26
Q

Where is the bulbar conjunctiva found?

A

Covering the sclera

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27
Q

Which conjunctiva is vascular: palprebral or bulbar?

A

bulbar

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28
Q

What does the lacrimal apparatus consist of? (4)

A

(1) Lacrimal gland and ducts
(2) Lacrimal canaliculi
(3) Lacrimal sac
(4) Nasolacrimal duct

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29
Q

Where is the lacrimal gland located?

A

Lacrimal fossa

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30
Q

What bone forms the lacrimal fossa?

A

Frontal bone

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31
Q

What muscle separates the lacrimal gland into two parts

A

levator palprebrae superioris

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32
Q

In which direction does fluid move over the eyeball?

A

Medially

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33
Q

What does the fluid moving over the eyeball accummulate in?

A

Lacrimal lake

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34
Q

What do the superior and inferior lacrimal canaliculus unite to form?

A

Lacrimal sac

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35
Q

How does fluid get from the lacrimal sac to the nasolacrimal duct?

A

During blinking, the palprebral part of the OO muscle contracts, forcing fluid into the nasolacrimal duct

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36
Q

Where does the nasolacrimal duct open into the nasal cavity?

A

Inferior nasal meatus

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37
Q

How much lacrimal fluid is produced per day?

A

1ml

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38
Q

What is the diameter of the eyeball?

A

2.5cm

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39
Q

How musch of the eyeball is exposed?

A

1/6

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40
Q

What ar the three layers of the wall of the eyeball?

A

(1) fibrous
(2) vascular
(3) Nervous/retina

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41
Q

What are the two componenets of the fibrous layer of the eye?

A

Sclera and cornea

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42
Q

What is the proper name for the white of the eye?

A

The sclera.

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43
Q

What structure at the front of the eye is the sclera continuous with?

A

The cornea

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44
Q

What is another name for the vascular layer of the eye?

A

Urea

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45
Q

What parts make up the vascular layer of the eye?

A

(1) choroid
(2) ciliary body
(3) iris

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46
Q

Where does the choroid get its blood supply from?

A

The posterior cilliary arteries.

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47
Q

What feature of the choroid helps limit uncontrolled reflection within the eye that could interfere with sight?

A

The presence of the dark pigment melanin.

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48
Q

What is the name for the layer of capillaries in the choroid?

A

Choriocapillaris.

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49
Q

What type of nerves control the cilliary muscle where do they originate from?

A

Parasympathtic fibers originating from the III cranial nerve (the occulomotor).

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50
Q

What makes up the ciliary body?

A

ciliary muscle and ciliary process

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51
Q

What is the effect of the contraction of the muscles of the cilliary body?

A

The ring made by the cilliary body shrinks reducing pressure on the lens allowing it to relax and become more convex (bulge out)

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52
Q

What type of muscle is the ciliary muscle?

A

smooth muscle

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53
Q

What does the ciliary process secrete?

A

Aqueous humor

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54
Q

What extends from the ciliary processes?

A

Suspensory filament of the lens / zonula fibres

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55
Q

what makes up the iris?

A

Melanocytes and radial and circular muscle

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56
Q

What determines the eye colour?

A

the amount of melanin

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57
Q

What happens when the circular muscles of the iris contract?

A

the pupil constrists

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58
Q

What innervates the circular muscle of the iris?

A

parasympathetic fibres of the oculomotor nerve

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59
Q

What happens when the radial muscles of the iris contract?

A

the pupil dilates

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60
Q

What innervates the radial muscle of the iris?

A

sympathetic fibres

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61
Q

What are the two parts of the retina?

A

Optic part, and non-visual part

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62
Q

what does the non-visual part of the retina cover?

A

Internal surface of the ciliary body and iris

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63
Q

What is the name for the junction between the visual parts of the retina and the anterior non-visual part of the retina

A

Ora serreta

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64
Q

Where does the optic nerve enter the eyeball?

A

Optic disc

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65
Q

What is the name for the blind spot of the retina what type of cells are not present that make this part non visual?

A

The optic disc, rod and cone cells are not present causing this area to be unable to process light.

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66
Q

What is the exact centre of the posterior portion of the eye called?

A

Macula lutea

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67
Q

What is at the centre of the macula lutea?

A

Fovea centralis

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68
Q

What is the fovea of the eye?

A

A small pit at the centre of the eye where most of the light is focused it contains a particularly high concentration of cone cells.

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69
Q

What part of the eye has highest acuity or resolution?

A

fovea

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70
Q

What are the two layers of the optic part of the retina?

A

The pigmented and neural layers.

71
Q

What layer of the retina becomes detached in a detached retina?

A

The neural layer.

72
Q

what is contained in the pigmented layer of the eye?

A

Melanin-containing epithelial cells

73
Q

What are the 3 layers of the neuronal layer of the optic retina?

A

(1) Photoreceptor layer/Outer nuclear
(2) Bipolar layer/Inner nuclear
(3) ganglion layer

74
Q

How many rods and cones does the retina have?

A

120 million rods

6 million cones

75
Q

What is the diameter of the lens?

A

9-10mm

76
Q

what proteins are found in the lens that make up the refractive media?

A

crystallins

77
Q

How are the crystallins of the lens organised?

A

Like the layers of an onion

78
Q

What is in the lens that ensures that the lens protein remains in a reduced state, and thus maintains the transparency?

A

reduced glutathione

79
Q

What are the three chambers of the eye?

A

The anterior, posterior and vitreous chamber.

80
Q

What are the anterior and posterior chambers filled with what opening connects the two?

A

The aqueous humor, the papillary opening connects the two chambers.

81
Q

What produces the aqueous humor what is its course including drainage?

A

It is produced by the cilliary body flows from the posterior chamber through the pupil into the anterior chamber it is then taken up into the sclera venous sinus/canal of schlemm

82
Q

Where is the sclera venous sinus/canal of schlemm?

A

The junction between the cornea and the iris.

83
Q

What is the junction between the cornea and iris called?

A

Canal of schlemm/sclera venous sinus

84
Q

What are the 3 functions of the aqueous humor?

A

(1) To supply nutrients to the avascular cornea and lens
(2) maintains the intraoccular pressure, and therefore the shape of the chamber
(3) acts as a suspension for the lens

85
Q

What is the name for the increase in intraoccular pressure caused by the disruption of the usual production and absorption of aqueous humor

A

glaucoma.

86
Q

How long does it take aqueous humor to be completely replaced?

A

90 minutes

87
Q

What makes up the vitreous humor that fills the vitrous chamber?

A

Mostly water very few cells which are mostly phagocytes, and a network of collagen fibres.

88
Q

What two structures does the vitreous humor keep together how does it do this?

A

The retina and the choroid. It keeps them attached by pressing them together.

89
Q

what is the normal intraocula pressure?

A

16mmHg

90
Q

What happens when light passes from one medium into another and the speed slows?

A

It bends towards a line that is perpendicular to the border.

91
Q

What is the distance called from the refractive surface to where the light rays converge

A

focal distance

92
Q

How much refraction occurs at the cornea?

A

75%

93
Q

How much refraction occurs at the lens?

A

25%

94
Q

what is a dioptre?

A

the reciprocal of the focal distance (in metres)

95
Q

What is it called when rays do not meet after the lens in one focal point?

A

Spherical abberation

96
Q

What is spherical abberation?

A

When rays do not meet after the lens in one focal point

97
Q

What is it called when a lens cannot focus all colours to the same convergence point?

A

chromatic abberation

98
Q

what is chromattic abberation

A

When there is failure of the lens to focus all colours to one convergence point

99
Q

What is binocular vision?

A

When both eyes focus on one set of objects

100
Q

What is convergence with respect to binocular vision?

A

the medial movement of the eyeballs so that they are both directed towards the same point

101
Q

How far does the visual field extend nasally? and temporarilly (away from nose)

A

nasally - 60 degrees

temporarily - 100 degrees

102
Q

how far does the visual field extend above and below the horizontal meridian?

A

60 degrees above

75 degrees below

103
Q

What is the binocular visual field?

A

The region of visual field that overlaps from both eyes

104
Q

What does visual acuity depend on?

A
  • precision of the eyes refraction

- spacing of photoreceptors

105
Q

What are the three glial cells in the retina?

A
  • muller cells
  • astrocytes
  • retinal pigment epithelial cells
106
Q

Where are muller cell bodies located?

A

Inner nuclear layer

107
Q

What two membranes do the muller cells form?

A

Internal limiting membrane

External limiting membrane

108
Q

How many discs are in a cone?

A

1000 discs

109
Q

What phagocytoses the discs?

A

pigment epithelial cells

110
Q

what is retinal derived from?

A

vitamin A

111
Q

What is photopic vision?

A

the contributions of rods to vision nearly drops out completely

112
Q

What is scotopic vision?

A

When only rods are activated - at the lowest levels of light

113
Q

What is mescopic vision

A

Both rods and cones contribute, at twilight for example.

114
Q

What are trichomats?

A

using a three-cone system to abdorb different wavelengths of light

115
Q

What are the three different populations of cones?

A

red
green
blue

116
Q

What is rhodopsin bleaching?

A

The conversion of 11-cis-retinal to all-trans-retinal, with the subsequent separation from opsin.

117
Q

what is different about the photopigments of rods and cones?

A

the retinal vitamin A derivative is the same, but the opsin meioty is different

118
Q

How many cones are there at the fovea (concentration)

A

199,000 cones per millimetre squared

119
Q

How big is the rod free zone in the fovea?

A

0.35mm

120
Q

What is photodecomposition?

A

The separation of all-trans-retinal from the rhodopsin

121
Q

What is formed in the conversion of 11-cis to all-trans that acts as an enzyme to activate transducin.

A

metarhodopsin II

122
Q

What deactivates meta II (activated rhodopsin)

A

rhodopsin kinase and arrestin

123
Q

What catalyses the isomeration of all-trans to 11-cis?

A

retinal isomerase.

124
Q

Via what kind of pathway is a signal produced when an opsin molecule absorbs a photon? What does this result in?

A

Signal transduction pathway activation of this kind of pathway results in the hyperpolarisation of the cell.

125
Q

What is the specialty of the rod cell? Where are they mostly found?

A

Sensation of low levels of light. They are found mostly on the periphery of the retina.

126
Q

What region of light are rods most sensitive to?

A

green to blue more specifically 498nm.

127
Q

What is meant by rod cells converging what is the advantage and disadvantage of this occurring?

A

Multiple rod cells converge on one interneuron. This collects and amplifies the signal however by doing this some resolution is lost.

128
Q

What neurotransmitter is released by rod and cone cells?

A

Glutamate.

129
Q

How is the release of glutamate affected by the absorption of photons?

A

It stops it.

130
Q

High concentration of what molecule in the dark allows the opening of of sodium and to a lesser extent calcium channels causing depolarization and the release of Glutamate.

A

cGMP

131
Q

What is the affect of the high levels cGMP on the intracellular activity of a rod cell?

A

It causes the opening of sodium and to a lesser extent calcium channels causing depolarisation.

132
Q

What enzyme is activated by the shape change of rhodopsin when it has absorbed a photon?

A

cGMP phosphodiesterase.

133
Q

What vitamin is contained within rhodopsin what is the effect of a deficiency of this vitamin?

A

Vitamin A, Night blindness is the result of a deficiency

134
Q

Why do cones have a higher resolution than rods?

A

Multiple rod cells attach to each interneuron. each cone attaches to an individual bipolar cell.

135
Q

What two types of cell transmit information between cells of the same layer in the retina?

A

amacrine and horizontal cells

136
Q

Which is most inner of the inner cell layer: amacrine or horizontal?

A

amacrine

137
Q

What are the 5 different populations of retinal ganglion cells?

A 
M/Magnocellular cells
P/Parvocellular cells
K cells
Photosensitive ganglions
Final population
138
Q

Describe the role of M/magnocellular cells?

A

Large center surround receptive fields, sensitive to depth but indifferent to color and adapts rapidly to stimulis

139
Q

Describe the role of P/Parvocellular cells?

A

Small centre surround receptive fields, sensitive to colour and shape.

140
Q

Describe the role of K cells?

A

Very large centre-only receptive fields, sensitive to colour but indifferent to shape and depth.

141
Q

Of the P layers in the lateral geniculate gyrus - which ones come from the ipsilateral eye?

A

P3 and P5

142
Q

Of the M layers in the lateral geniculate gyrus - which one comes from the ipsilateral eye?

A

2

143
Q

Where is the optic chiasm?

A

At the base of the hypothalamus

144
Q

what layer of the primary visual cortex do magnocellular neurons project to?

A

Layer IVc-alpha

145
Q

what layer of the primary visual cortex do parvocellular neurons project to?

A

Layer IVc-beta

146
Q

What are blobs in the primary visual cortex?

A

sections where groups of neurons that are sensitive to colour assemble

147
Q

What are interblobs in the primary visual cortex?

A

Areas between blobs where neurons sensitive to orientation assemble.

148
Q

What are the different cells found in the primary visual cortex?

A
  • centre surround
  • simple cells (edge determination)
  • complex cells
  • hypercomplex cells
149
Q

What layer do the fibres from the P and M cells insert into?

A

4c

150
Q

What are the other targets of ganglion axons?

A

MIDBRAIN TARGETS:

(1) pretectum
(2) hypothalamus
(3) Superior colliculus

151
Q

what is the role of the pretectum?

A

control of pupil - papillary light reflex

152
Q

What is the role of hypothalamus?

A

carcadian rhythm (day/night)

153
Q

What is the role of the superior colliculus

A

eye movements (involuntary)

154
Q

What is blindsight?

A

ability of people who are cortically blind due to lesions in their striate cortex to respond to visual stimuli that they do not consciously see

155
Q

What is another name given to pupil constriction?

A

miosis

156
Q

what is another name given to pupil constriction?

A

mydriasis

157
Q

what is the consensual response?

A

pupillar reflex of the unstimulated eye

158
Q

What is a relative afferent papillary defect?

A

Damage to either the optic nerve or occulomotor nerve that affects the pupillary reflex

159
Q

what is strabismus?

A

Cross eye - lack of fusion of the eyes due to lack of coordination of the extraocular muscles

160
Q

Strabismus - what would an impairment of [CN III] cause?

A

Affected eye to deviate down and out

lateral rectus pulls it out, superior oblique pulls it down

161
Q

Strabismus - what would an impairment of [CN IV] cause?

A

Affected eye to drift up and slightly in

162
Q

What is amblyopia?

A

decreased vision in an eye that otherwise appears normal

163
Q

What is anisometropia?

A

Inequality of refraction of the eyes

164
Q

What is cataract?

A

Opacification of the lens

165
Q

what is hypermetropia?

A

long-sightedness

166
Q

How is hypermetropia treated?

A

Convex lens

167
Q

What is a convex lens - positive or negative?

A

positive

168
Q

what is myotropia?

A

Shortsightedness

169
Q

How is myopia treated?

A

Concave lens

170
Q

What is a concave lens - positive or negative?

A

negative

171
Q

what is astigmatism?

A

corneal surface is asymmetric

172
Q

How does a pituitary tumour affect vision?

A

Pituitary gland is located just inferior to the optic chiasm

173
Q

What is macular sparing?

A

the central 5-10 degrees of the visual field is unaffected in an otherwise hemo-anopic defect.

174
Q

what is anopia?

A

sightlessness

Sem 3 (6 decks)

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