Case 3 Flashcards
1
Q
What are the three chambers of the eye?
A
The anterior, posterior and vitreous chamber.
2
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.
3
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
4
Q
Where is the sclera venous sinus/canal of schlemm?
A
The junction between the cornea and the iris.
5
Q
What are the two functions of the aqueous humor?
A
To supply nutrients to the avascular cornea and lens and maintains the intraoccular pressure.
6
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.
7
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 fibers.
8
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.
9
Q
What are the three layers of the walls of the eyeball?
A
the sclera, choroid and the retina.
10
Q
What is the name for the outer fibrous layer of the eye.
A
The sclera.
11
Q
What is the name for the middle vaascular wall of the eyeball.
A
The choroid.
12
Q
What is the proper name for the white of the eye?
A
The sclera.
13
Q
What structure at the front of the eye is the sclera continuous with?
A
The cornea
14
Q
What do the muscles that move the eyes insert into.
A
The sclera.
15
Q
Where do the posterior cilliary arteries that supply the choroid originate from?
A
The opthalmic artery.
16
Q
Where does the choroid get its blood supply from?
A
The posterior cilliary arteries.
17
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.
18
Q
What re the four layers of the choroid?
A
Haller’s layer, Sattler’s layer, Choriocapillaris and Bruch’s membrane
19
Q
Which three layers of the choroid contain blood vessels list them in order of largest blood vessels to smallest?
A
Haller’s layer, Sattler’s layer, Choriocapillaris.
20
Q
What is the name for the layer of capillaries in the choroid?
A
Choriocapillaris.
21
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).
22
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 become narrower and more convex.
23
Q
What type of nerve fiber supplies the sphincter pupillae muscle?
A
Parasympathetic fibers.
24
Q
What type of nerve fiber supplies the dilator pupillae muscle?
A
Sympathetic fibers
25
What is the name for the junction between the posterior and lateral visual parts of the retina and the anterior non visual part of the retina which coats the cilliary body.
The ora serrata
26
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.
27
What leaves the eye via the optic disc what do these form
Ganglion cell axons these eventually form the optic nerve.
28
What are the two layers of the retina?
The pigmented and neural layers.
29
What layer of the retina becomes detached in a detached retina?
The neural layer.
30
Branches of what artery spread out from the optic disc?
The central retinal artery.
31
Describe the course of light through the eye to the retina?
Light passes through the cornea be refracted when it does so, passes through the pupil is refracted further by the lens and then passes to the retina.
32
What are the two types of opsin which type is present in rods and what in cones?
Rhodopsin in rods and iodopsin in cones.
33
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.
34
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.
35
What region of light are rods most sensitive to?
green to blue more specifically 498nm.
36
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.
37
What neurotransmitter is released by rod and cone cells?
Glutamate.
38
How is the release of glutamate effected by the absorption of photons?
It stops it.
39
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
40
What is the effect 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.
41
What enzyme is activated by the shape change of rhodopsin when it has absorbed a photon?
cGMP phosphodiesterase.
42
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.
43
What is the fovea of the eye?
A small pit at the center of the eye where most of the light is focused it contains a particularly high concentration of cone cells.
44
What are the three types of iodopsin that are found within the cone cells of the retina?
L/long, M/medium and S/short
45
How are the cones distributed in the eye?
the highest concentration is in the fovea of the eye their concentration drops off considerably at you reach the periphery of the eye.
46
What are the relative populations of rods and cones in the eye?
4.5 million cones to 120 million rods
47
Why do cones have a higher resolution than rods?
Multiple rod cells attach to each interneuron. each cone attaches to an individual bipolar cell.
48
What do bipolar cells in the retina synapse with apart from their photosensitive cell? What is the role of this cell?
A ganglion cell which conduct the action potentials to the brain.
49
What is a center surround receptive field
The area in space that light from will stimulate a given ganglion cell.
50
What two types of cell transmit information between cells of the same layer in the rentina?
amacrine and horizontal cells.
51
What are the 5 different populations of retinal ganglion cells?
M/Magnocellular cells, P/Parvocellular cells, K cells, Photosensitive ganglions and final population.
52
Describe the role of M/magnocellular cells?
Large center surround receptive fields, sensitive to depth but indifferent to color and adapts rapidly to stimulis
53
Describe the role of P/Parvocellular cells?
Small center surround receptive fields, sensitive to color and shape.
54
Describe the role of K cells?
Very large center surround receptive fields, sensitive to color but indifferent to shape and depth.
55
Describe the role of Photosensitive ganglion cells.
They are intrinsically photosensitive they produce signals from within the ganglia.
56
Describe the role of the final population cells.
Aiding the control of eye movements.
57
Describe the difference between on center and off center ganglion cells.
On ganglion cells are activated when the bipolar cells in the center of their surround receptive field are activated and turned off when bipolar cells on the periphery of their receptive field are excited in Off center ganglion cells react oppositely .
58
What part of an image does lateral inhibition help define?
Contrast detection.
59
What cells activate horizontal cells in lateral inhibition?
Non central bipolar cells.
60
What cell is inhibited by the horizontal cells in lateral inhibition?
The central bipolar cell of a receptive field.
61
Where do the majority of the axons of the optic nerve travel to?
The lateral geniculate nucleus.
62
From which retina populations do the axons traveling to the lateral geniculate nucleus arise from?
M, P and K
63
Where do the axons arising from the final population of ganglion cells travel to what function do they serve?
The superior colliculus in the midbrain assisting with the control of eye movements.
64
Where is the optic chisma?
The base of the hypothalmus
65
What is the optic chiasma?
The point where the optic nerves from each eye meet and cross.
66
How do the nerves before and after the optic chiasma differ in terms of origin?
Before the the optic chiasma each optic nerve caries information from its ipsilateral eye after the optic tract splits according to visual field the left tract carrying information from the right visual field from each eye and the right tract the left visual field.
67
What are the nerve carrying information from the optic chiasma to the lateral geniculate nucleus called?
The optic tract.
68
How many layers does the lateral geniculate nucleus contain?
6
69
Which layers of each geniculate nucleus deal with efferents from the contralateral nasal visual field?
1, 4 and 6
70
Which layers of each geniculate nucleus deal with efferents from the ipsilateral temporal field?
2, 3 and 5
71
What is the specialty of layer 1 of the geniculate nucleus what type of cells does it contain?
It contains M cells which correspond to M cells in the ganglion of the contralateral eye and is concerned with depth and motion.
72
What type of cells do layers 4 and 6 of the geniculate nucleus contain? what is their specialty?
P cells from the contraleteral eye which are concerned color and edges/shape.
73
What type of cells do layers 2, 3 and 5 receive information from?
M and P
74
What is in between layers 1 through 6 what is it's function?
Smaller layers that receive information from K cells and are concerned with color
75
What carries information the geniculate nucleus to the primary visual cortex?
The radiation fibers
76
what are the radiation fibers?
the nerve fibers that link the geniculate nucleus and the primary visual cortex.
77
Where is the primary visual cortex?
The occipital lobe at the back of the brain either side of the calcarine fissure.
78
What is the course of the radiating fibers through the brain to the primary motor cortex?
The radiating fibers split into 2 paths ones carrying information on the superior visual field/inferior portion of the retina travel via the temporal lobe ones carrying information on the inferior visual field/superior portion of the retina travel via the parietal lobe.
79
Information from what portion of the eye is processed by the the most posterior portion of the visual cortex?
the macular.
80
What areas does the visual cortex process information from as you go from the most posterior section forward?
It starts from the macular and then as you move forward it processes concentric circles moving outwards.
81
What is the direct pupillary reflex?
When the pupil constricts due to light being shone on it
82
What is the consensual pupillary reflex?
When a pupil constricts in reaction to a light being shone in the other eye.
83
What cells convey the information regarding the pupillary reflexes first?
retinal ganglion cells.
84
Where does the information regarding the pupillary reflexes travel after entering the optic nerve?
Into the pretectal nucleus of the high midbrain.
85
Where does information regarding pupillary reflexes travel to after the pretectal nucleus?
Edinger-Westphal nucleus.
86
Where does information regarding pupillary reflexes travel to after the edinger westphal nucleus?
Via the occulomotor nerves (III) to the ciliary ganglion neurons.
87
What is the role of ciliary ganglion neurons in pupillary reflexes?
The innervate the the constrictor muscles of the iris.
88
If there is damage to the left optic nerve which pupillary reflexes are affected?
Left direct and right consensual
89
If there is damage to the right optic nerve which pupillary reflexes are effected?
right direct and left consensual
90
If there is damage to the left occulomotor nerve which pupillary reflexes are effected?
Left direct and right consensual
91
If there is damage to the right occulomotor nerve which pupillary reflexes are effected?
right direct and left consensual
92
What is Amblyopia?
The functional reduction in the visual acuity of the eye caused by disuse of the eye during its visual development.
93
What time is it important to correct amblyopia before why is this?
The age of 8 as this is when visual development finishes
94
When does visual development occur?
mostly before the age of three but up until age 8
95
When does amblyopia occur?
when there is persistent interference with the image from one eye but not the other.
96
How does the visual cortex respond to amblyopia? What happens if this happens for too long?
The visual cortex responds by suppressing the image from the disturbed eye if this suppression occurs for too long the visual loss can become permanent.
97
What are the two ages important for the treatment of amblyopia?
Age three as this is the age most visual development takes place before and age 8 as this is when visual development finishes.
98
What is strabismus how does it cause amblyopia?
A condition where the eyes are misaligned appering cross eyed. It causes amblyopia as the two eyes do not produce similar retinal images
99
What is ansiometropia?
an inequality of the refraction of the eyes.
100
How does ansiometropia cause amblyopia?
The two retinal images coming from the eyes have different focus.
101
What are the three main causes of amblyopia?
Ansiometropia, strabismus and obstruction of the visual axis.
102
When does treatment for amblyopia need to start in order for there to be significant improvement?
age 5
103
What are the two tests most useful for diagnosis of amblyopia?
snellen test and photoscreening
104
how is the snellen test used to screen children for amblyopia?
the visual acuity of each eye is checked individually to see if there is a difference.
105
well are children usually screened for amblyopia?
before they start school, around the age of 3
106
What are the causes of strabismus?
mostly often refractive errors or muscle imbalances but rarely cancer and neurologic disease.
107
What are the two types of strabismus?
congenital and acquired.
108
What are the risk factors for strabismus?
family history, prenatal drug exposure, prematurity/low birthweight congenital eye defects and cerebral palsy.
109
What can acquired strabismus be the result of?
tumors, head trauma spina bifida, viral infections
110
When would eyeglasses or contact lenses be an appropriate treatment for strabismus?
When the strabismus is cause by a significant refractive error.
111
What are three common treatments for strabismus?
eyeglasses/contact lenses, oprthoptic eye exercises and surgery.
112
What are the two types of surgery that can be used to treat strabismus?
recession/ loosening and resection/tightening surheries.
113
What is the name for the eyes ability to focus on objects at different distances?
accommodation.
114
What does the term refractive error refer to?
an abnormality in the focusing mechanism of the eye and not to any opacity caused by scaring etc.
115
What is the colloquial name for myopia?
shortsightedness
116
what is the proper name for shortsightedness?
myopia.
117
What is the colloquial name for hyperopia?
farsightedness
118
What is the proper name for farsightedness?
hyperopia.
119
What is the cause of myopia?
The retina being too steeply curve, the eye being too long or a combination of the two.
120
What type of lens would you give to someone with myopia?
concave.
121
How does the myopia of a child progress as they are growing?
It usually gets worse as they develop.
122
What causes farsightedness?
The lens of the eye being too flat the eye being too short or a combination of the two.
123
What kind of lens would you give to someone with hyperopia?
convex.
124
What is astigmatism?
When the cornea or the lens has a not spherical curvature and resembles a rugby ball more than a football.
125
what type of lens is used to treat astigmatism when is this and what feature of astigmatism is this because of?
a cylindrical lens as they have no refractive power on one axis but are convex/concave in others as in astigmatism an eye can be hyeropic in one plane and myopic or emmetropic in others.
126
What emmetropic mean?
that the eye is functioning well.
127
What are the two main symptoms of refractive errors besides blurred vision what causes them?
headaches caused by excessive ciliary muscle definition and desiccation resulting in irritation, itching and visual fatigue caused by excessive staring trying to focus.
128
What is bitemporal hemianopia a lesion where would cause this?
bitemporal hemianopia is where light from the temporal field is not detected in either eye it can be caused by a lesion in the optic chiasma as this will interrupt the nasal aspect of the retina which receives information from the temporal field.
129
A lesion where would cause the loss of the right visual field?
The left optic tract
130
A lesion where would cause the loss of the left visual field?
The right optic tract
131
A lesion where would cause the loss of the left superior visual field
the right temporal radiation fibers.
132
A lesion where would cause the loss of the left inferior visual field?
the right parietal radiation fibers.
