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
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
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
4
Q
What is the name given to the space between the eyelids when they are open?
A
Palprebral fissure
5
Q
What are the angles of the palprebral fissure called?
A
Medial and lateral commissure
6
Q
Which is bigger, the medial or lateral commissure?
A
Medial
7
Q
What is found in the medial commisure?
A
Lacrimal caruncle
8
Q
What is the reddish elavation in the medial commissure that contains oil and sweat glands?
A
Larcrimal caruncle
9
Q
What is found in the lacrimal caruncle?
A
Oil and sweat glands
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
11
Q
What are the two parts to the orbicularis oculi muscle?
A
Orbital part and palprebrae part
12
Q
What innervates the orbicularis oculi muscle?
A
Facial nerve
13
Q
What is the role of the orbucularis oculi muscle?
A
To close the eyelids
14
Q
What ligaments anchor the palprebral part of the OO muscle?
A
Medial and lateral palprebral ligaments
15
Q
What is the tarsal plate?
A
A thick fold of connective tissue
16
Q
Which is bigger: superior or inferior tarsus?
A
superior tarsus
17
Q
What muscle is the superior tarsus associated with?
A
Levator palprebrae muscle
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.
19
Q
Where does the levator palprebrae muscle extend from?
A
Lesser wing of sphenoid (to the superior tarsus muscle).
20
Q
What type of glands are the tarsus glands?
A
sebacceous (oil) glands
21
Q
What is another name given to the tarsus glands?
A
Meibomian glands
22
Q
What does infection of a tarsal gland cause?
A
A cyst called a chalzion.
23
Q
What is conjunctiva?
A
non-keratinised stratified columnar epithelium
24
Q
What are the two types of conjunctiva?
A
Palprebral and bulbar
25
where is palprebral conjunctiva found?
On the inner aspects of eyelids
26
Where is the bulbar conjunctiva found?
Covering the sclera
27
Which conjunctiva is vascular: palprebral or bulbar?
bulbar
28
What does the lacrimal apparatus consist of? (4)
(1) Lacrimal gland and ducts
(2) Lacrimal canaliculi
(3) Lacrimal sac
(4) Nasolacrimal duct
29
Where is the lacrimal gland located?
Lacrimal fossa
30
What bone forms the lacrimal fossa?
Frontal bone
31
What muscle separates the lacrimal gland into two parts
levator palprebrae superioris
32
In which direction does fluid move over the eyeball?
Medially
33
What does the fluid moving over the eyeball accummulate in?
Lacrimal lake
34
What do the superior and inferior lacrimal canaliculus unite to form?
Lacrimal sac
35
How does fluid get from the lacrimal sac to the nasolacrimal duct?
During blinking, the palprebral part of the OO muscle contracts, forcing fluid into the nasolacrimal duct
36
Where does the nasolacrimal duct open into the nasal cavity?
Inferior nasal meatus
37
How much lacrimal fluid is produced per day?
1ml
38
What is the diameter of the eyeball?
2.5cm
39
How musch of the eyeball is exposed?
1/6
40
What ar the three layers of the wall of the eyeball?
(1) fibrous
(2) vascular
(3) Nervous/retina
41
What are the two componenets of the fibrous layer of the eye?
Sclera and cornea
42
What is the proper name for the white of the eye?
The sclera.
43
What structure at the front of the eye is the sclera continuous with?
The cornea
44
What is another name for the vascular layer of the eye?
Urea
45
What parts make up the vascular layer of the eye?
(1) choroid
(2) ciliary body
(3) iris
46
Where does the choroid get its blood supply from?
The posterior cilliary arteries.
47
What feature of the choroid helps limit uncontrolled reflection within the eye that could interfere with sight?
The presence of the dark pigment melanin.
48
What is the name for the layer of capillaries in the choroid?
Choriocapillaris.
49
What type of nerves control the cilliary muscle where do they originate from?
Parasympathtic fibers originating from the III cranial nerve (the occulomotor).
50
What makes up the ciliary body?
ciliary muscle and ciliary process
51
What is the effect of the contraction of the muscles of the cilliary body?
The ring made by the cilliary body shrinks reducing pressure on the lens allowing it to relax and become more convex (bulge out)
52
What type of muscle is the ciliary muscle?
smooth muscle
53
What does the ciliary process secrete?
Aqueous humor
54
What extends from the ciliary processes?
Suspensory filament of the lens / zonula fibres
55
what makes up the iris?
Melanocytes and radial and circular muscle
56
What determines the eye colour?
the amount of melanin
57
What happens when the circular muscles of the iris contract?
the pupil constrists
58
What innervates the circular muscle of the iris?
parasympathetic fibres of the oculomotor nerve
59
What happens when the radial muscles of the iris contract?
the pupil dilates
60
What innervates the radial muscle of the iris?
sympathetic fibres
61
What are the two parts of the retina?
Optic part, and non-visual part
62
what does the non-visual part of the retina cover?
Internal surface of the ciliary body and iris
63
What is the name for the junction between the visual parts of the retina and the anterior non-visual part of the retina
Ora serreta
64
Where does the optic nerve enter the eyeball?
Optic disc
65
What is the name for the blind spot of the retina what type of cells are not present that make this part non visual?
The optic disc, rod and cone cells are not present causing this area to be unable to process light.
66
What is the exact centre of the posterior portion of the eye called?
Macula lutea
67
What is at the centre of the macula lutea?
Fovea centralis
68
What is the fovea of the eye?
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.
69
What part of the eye has highest acuity or resolution?
fovea
70
What are the two layers of the optic part of the retina?
The pigmented and neural layers.
71
What layer of the retina becomes detached in a detached retina?
The neural layer.
72
what is contained in the pigmented layer of the eye?
Melanin-containing epithelial cells
73
What are the 3 layers of the neuronal layer of the optic retina?
(1) Photoreceptor layer/Outer nuclear
(2) Bipolar layer/Inner nuclear
(3) ganglion layer
74
How many rods and cones does the retina have?
120 million rods
| 6 million cones
75
What is the diameter of the lens?
9-10mm
76
what proteins are found in the lens that make up the refractive media?
crystallins
77
How are the crystallins of the lens organised?
Like the layers of an onion
78
What is in the lens that ensures that the lens protein remains in a reduced state, and thus maintains the transparency?
reduced glutathione
79
What are the three chambers of the eye?
The anterior, posterior and vitreous chamber.
80
What are the anterior and posterior chambers filled with what opening connects the two?
The aqueous humor, the papillary opening connects the two chambers.
81
What produces the aqueous humor what is its course including drainage?
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
Where is the sclera venous sinus/canal of schlemm?
The junction between the cornea and the iris.
83
What is the junction between the cornea and iris called?
Canal of schlemm/sclera venous sinus
84
What are the 3 functions of the aqueous humor?
(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
What is the name for the increase in intraoccular pressure caused by the disruption of the usual production and absorption of aqueous humor
glaucoma.
86
How long does it take aqueous humor to be completely replaced?
90 minutes
87
What makes up the vitreous humor that fills the vitrous chamber?
Mostly water very few cells which are mostly phagocytes, and a network of collagen fibres.
88
What two structures does the vitreous humor keep together how does it do this?
The retina and the choroid. It keeps them attached by pressing them together.
89
what is the normal intraocula pressure?
16mmHg
90
What happens when light passes from one medium into another and the speed slows?
It bends towards a line that is perpendicular to the border.
91
What is the distance called from the refractive surface to where the light rays converge
focal distance
92
How much refraction occurs at the cornea?
75%
93
How much refraction occurs at the lens?
25%
94
what is a dioptre?
the reciprocal of the focal distance (in metres)
95
What is it called when rays do not meet after the lens in one focal point?
Spherical abberation
96
What is spherical abberation?
When rays do not meet after the lens in one focal point
97
What is it called when a lens cannot focus all colours to the same convergence point?
chromatic abberation
98
what is chromattic abberation
When there is failure of the lens to focus all colours to one convergence point
99
What is binocular vision?
When both eyes focus on one set of objects
100
What is convergence with respect to binocular vision?
the medial movement of the eyeballs so that they are both directed towards the same point
101
How far does the visual field extend nasally? and temporarilly (away from nose)
nasally - 60 degrees
| temporarily - 100 degrees
102
how far does the visual field extend above and below the horizontal meridian?
60 degrees above
| 75 degrees below
103
What is the binocular visual field?
The region of visual field that overlaps from both eyes
104
What does visual acuity depend on?
- precision of the eyes refraction
| - spacing of photoreceptors
105
What are the three glial cells in the retina?
- muller cells
- astrocytes
- retinal pigment epithelial cells
106
Where are muller cell bodies located?
Inner nuclear layer
107
What two membranes do the muller cells form?
Internal limiting membrane
| External limiting membrane
108
How many discs are in a cone?
1000 discs
109
What phagocytoses the discs?
pigment epithelial cells
110
what is retinal derived from?
vitamin A
111
What is photopic vision?
the contributions of rods to vision nearly drops out completely
112
What is scotopic vision?
When only rods are activated - at the lowest levels of light
113
What is mescopic vision
Both rods and cones contribute, at twilight for example.
114
What are trichomats?
using a three-cone system to abdorb different wavelengths of light
115
What are the three different populations of cones?
red
green
blue
116
What is rhodopsin bleaching?
The conversion of 11-cis-retinal to all-trans-retinal, with the subsequent separation from opsin.
117
what is different about the photopigments of rods and cones?
the retinal vitamin A derivative is the same, but the opsin meioty is different
118
How many cones are there at the fovea (concentration)
199,000 cones per millimetre squared
119
How big is the rod free zone in the fovea?
0.35mm
120
What is photodecomposition?
The separation of all-trans-retinal from the rhodopsin
121
What is formed in the conversion of 11-cis to all-trans that acts as an enzyme to activate transducin.
metarhodopsin II
122
What deactivates meta II (activated rhodopsin)
rhodopsin kinase and arrestin
123
What catalyses the isomeration of all-trans to 11-cis?
retinal isomerase.
124
Via what kind of pathway is a signal produced when an opsin molecule absorbs a photon? What does this result in?
Signal transduction pathway activation of this kind of pathway results in the hyperpolarisation of the cell.
125
What is the specialty of the rod cell? Where are they mostly found?
Sensation of low levels of light. They are found mostly on the periphery of the retina.
126
What region of light are rods most sensitive to?
green to blue more specifically 498nm.
127
What is meant by rod cells converging what is the advantage and disadvantage of this occurring?
Multiple rod cells converge on one interneuron. This collects and amplifies the signal however by doing this some resolution is lost.
128
What neurotransmitter is released by rod and cone cells?
Glutamate.
129
How is the release of glutamate affected by the absorption of photons?
It stops it.
130
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.
cGMP
131
What is the affect of the high levels cGMP on the intracellular activity of a rod cell?
It causes the opening of sodium and to a lesser extent calcium channels causing depolarisation.
132
What enzyme is activated by the shape change of rhodopsin when it has absorbed a photon?
cGMP phosphodiesterase.
133
What vitamin is contained within rhodopsin what is the effect of a deficiency of this vitamin?
Vitamin A, Night blindness is the result of a deficiency
134
Why do cones have a higher resolution than rods?
Multiple rod cells attach to each interneuron. each cone attaches to an individual bipolar cell.
135
What two types of cell transmit information between cells of the same layer in the retina?
amacrine and horizontal cells
136
Which is most inner of the inner cell layer: amacrine or horizontal?
amacrine
137
What are the 5 different populations of retinal ganglion cells?
```
M/Magnocellular cells
P/Parvocellular cells
K cells
Photosensitive ganglions
Final population
```
138
Describe the role of M/magnocellular cells?
Large center surround receptive fields, sensitive to depth but indifferent to color and adapts rapidly to stimulis
139
Describe the role of P/Parvocellular cells?
Small centre surround receptive fields, sensitive to colour and shape.
140
Describe the role of K cells?
Very large centre-only receptive fields, sensitive to colour but indifferent to shape and depth.
141
Of the P layers in the lateral geniculate gyrus - which ones come from the ipsilateral eye?
P3 and P5
142
Of the M layers in the lateral geniculate gyrus - which one comes from the ipsilateral eye?
2
143
Where is the optic chiasm?
At the base of the hypothalamus
144
what layer of the primary visual cortex do magnocellular neurons project to?
Layer IVc-alpha
145
what layer of the primary visual cortex do parvocellular neurons project to?
Layer IVc-beta
146
What are blobs in the primary visual cortex?
sections where groups of neurons that are sensitive to colour assemble
147
What are interblobs in the primary visual cortex?
Areas between blobs where neurons sensitive to orientation assemble.
148
What are the different cells found in the primary visual cortex?
- centre surround
- simple cells (edge determination)
- complex cells
- hypercomplex cells
149
What layer do the fibres from the P and M cells insert into?
4c
150
What are the other targets of ganglion axons?
MIDBRAIN TARGETS:
(1) pretectum
(2) hypothalamus
(3) Superior colliculus
151
what is the role of the pretectum?
control of pupil - papillary light reflex
152
What is the role of hypothalamus?
carcadian rhythm (day/night)
153
What is the role of the superior colliculus
eye movements (involuntary)
154
What is blindsight?
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
What is another name given to pupil constriction?
miosis
156
what is another name given to pupil constriction?
mydriasis
157
what is the consensual response?
pupillar reflex of the unstimulated eye
158
What is a relative afferent papillary defect?
Damage to either the optic nerve or occulomotor nerve that affects the pupillary reflex
159
what is strabismus?
Cross eye - lack of fusion of the eyes due to lack of coordination of the extraocular muscles
160
Strabismus - what would an impairment of [CN III] cause?
Affected eye to deviate down and out
| lateral rectus pulls it out, superior oblique pulls it down
161
Strabismus - what would an impairment of [CN IV] cause?
Affected eye to drift up and slightly in
162
What is amblyopia?
decreased vision in an eye that otherwise appears normal
163
What is anisometropia?
Inequality of refraction of the eyes
164
What is cataract?
Opacification of the lens
165
what is hypermetropia?
long-sightedness
166
How is hypermetropia treated?
Convex lens
167
What is a convex lens - positive or negative?
positive
168
what is myotropia?
Shortsightedness
169
How is myopia treated?
Concave lens
170
What is a concave lens - positive or negative?
negative
171
what is astigmatism?
corneal surface is asymmetric
172
How does a pituitary tumour affect vision?
Pituitary gland is located just inferior to the optic chiasm
173
What is macular sparing?
the central 5-10 degrees of the visual field is unaffected in an otherwise hemo-anopic defect.
174
what is anopia?
sightlessness
