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Visual System Flashcards

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1
Q

Name the extrinsic muscles of the eye innervated by CNIII

A 
SR
IR
MR
IO
levator of upper eyelid
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2
Q

Name the extrinsic muscle of the eye innervated by CNIV

A

SO

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3
Q

Name the extrinsic muscle of the eye innervated by CN VI

A

LR

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4
Q

Name the intrinsic muscles of the eye innervated by CNIII

A 
ciliary body (accomodation)
circular constrictor (miosis)
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5
Q

Name the intrinsic muscle innervated by sympathetic ganglion

A

dilator muscle (mydriasis)

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6
Q

Near Synkinesis includes:

A

Convergence (CNIII-MR)
Accommodation (CN-contraction of ciliary muscle)
Miosis (CNIII- PSNS, pupils constrict)

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7
Q

Name the three layers of the eye

A

Outer layer
Middle layer
Inner layer

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8
Q

Name the three outer layer structures of the eye

A

Cornea (clear, reflects light anteriorly)
Sclera (posterior)
Limbus (corneoscleral jxn)

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9
Q

Name the three middle layer structures of the eye

A

Iris (radial and circular smooth muscles)
Ciliary body (ciliary muscle, accommodation)
Choroid (Vascular supply to the RPE, outer retina)

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10
Q

Name the structures in the inner layer of the eye

A

Retinal pigmented epithelium
Neural retinal (ends at ora serrata)
- outer retina: photorecepters (primary neurons)
- inner retina: bipolar cells (secondary neurons) and ganglion tertiary neurons

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11
Q

What supplies blood to inner retina

A

Central retinal artery

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12
Q

What supplies blood to the outer retina

A

Choroidal arteries

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13
Q

Progression from photoreceptors to bipolar cells is modulated by

A

horizontal cells

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14
Q

Progression from bipolor cells to ganglion cells is modulated by

A

amacrine cells

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15
Q

How is the optic nerve clinically determined

A

contour
color
cupping

  • eight point eye exam
  • No photoreceptors in the optic nerve head= blind spot
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16
Q

Lamina cribosa is modified sclera surrounded by

A

unmyelinated ganglion axons

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17
Q

What are the two “glue down” points for the retina

A

Ora serrata and optic nerve

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18
Q

What is the interface b/t the apical surface of the neural retina (photoreceptors) and the RPE called

A

subretinal space

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19
Q

Where is the site for most retinal detachments

A

subretinal space

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20
Q

What five forces attach the RPE to the neural retina

A

RPE microvili interdigitate with photoreceptor outer segments

Mucopolysaccharide matrix glue in subretinal space

A cone outer segment domain of mucus

Water flux from vitreous across neural retina into choroidal vessels (driven by RPE ionic pumps)

Jelly-like nature of vitreous body

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21
Q

What is the Macula

A

Cone dense area that contains innermost foveola and fovea.

*fovea has no inner retinal vasculature

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22
Q

Name the layers from the sclera to the ganglion cells of the inner retina

A

Sclera»Choroid»RPE»Outer Nuclear L.»Outer Plexiform L.»Inner. Nuclear L»Inner Plexiform»Ganglion cell

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23
Q

Ganglion cells are

A

third order neurons, exit globe as optic nerve. Three varieties

  1. Parvocellular (X)
  2. Magnocellular (Y)
  3. W axons
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24
Q

Parvocellular (X) ganglion cells specialize in

A

fine detail “what pathway”

40% of retina

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25
Magnocellular (Y) ganglion cells specialize in
gross movement "where" pathway 40% of retina
26
W axons specialize in
responding to light intensity, covers the whole retina 20% of retina *Never will go to LGN, goes to suprachiasmatic nucleus (circadian rhythm) and Edinger-Westphal nucleus (pupil response to light)
27
how do Photoreceptors respond to light
hyperpolerize to light
28
What are the two varieties of photoreceptors
Rods Cones
29
What are the characteristics of Rods
Scotopic (night vision) peripherally located-absent in foveola & fovea high sensitivity low acquity * surrounded by few RPE microvilli with low density of melanosomes (light absorbing pigments)
30
What are the characteristics of Cones
Photopic (color vision) centrally located adn concentrated at the fovea low sensitivity high acquity * Surrounded by MANY RPE with MANY melanosomes - allows the capturing of light that enters the eye STRAIGHT= Directional sensitivity
31
The foveola is the point of highest visual acquity, why?
Miniaturization (concentrates tiny cones) for higher resolution neural retina is thinnest here (least amount of light distortion)
32
What test appraises the retinal function
electroretinogram (ERG)- tests phototopic/scotopic vision of entire or unique spot on retina
33
How is ERG performed
An electrode is placed on the sclera with another grounded to the forehead. Pulses of light reveal: a wave depression-photoreceptor fx b wave rise-bipolar fx c wave slow rise- RPE fx
34
What is amplification
One activate rhodopsin molecule causes hundreds of outer segment Na channels to close.
35
CGMP is responsible for
keeping photoreceptors tonically depolorized by providing a constant supply of NA ions (dark current)
36
What the biochemical events associated with vision
Photon of light hits optic discs embedded in photoreceptors>>Rhodopsin/Vitamin A moeity changes from cis to trans and dissociates from opsin>>Opsin activated>>transducin to bind GTP>>>Phosphodiesterase activated PDE catalyzes conversion of CGMP to 5'GMP>>Na channels close>>photoreceptors HYPERPOLORIZE (glutamate ceases)>>VISION
37
What type of cilia does photoreceptors have
9+0 with no motor protein so, immotile cilia syndromes have no effect on vision
38
How many rod disc exists in the outer segment of photoreceptors
1000 * 100 new discs made basally every day. The oldest discs are phagocytized by the RPE in a circadian rhythm. * same with the cones
39
How are scotomas tested
One eye at a time Perimetry or Confrontation exam Drawn as pt sees visual world
39
A pituitay tumor may push up on the inferior fibers of the chiasm and cause a
Partial heteronomous hemianopsia
40
What are scotomas
blind spots in the visual world, due to photoreceptor absense in the optic nerve, or disease. The image crosses over and the patient fills the scotoma
41
A partial inferior heteronomous hemianopsia is the result of
craniopharyngioma that impinges on the superior fibers of the chiasm.
42
What is the pathway for the superior visual worlds projection onto the retina
Superior visual world projects to the INFERIOR retina. Axons from inferior retina remain inferior in the optic nerve, chiasm, optic radiations (via MEYERS loop) in temporal lobe, and go to the inferior bank of the calcarine fissure
43
Optic tract lesions are considered non-localizing because
the loss of left or right visual fields (depending on which optic tract lesioned) can result from optic tract lesions, massive occipital knock out by stroke
43
What are the five functions of the RPE
1. Create blood/photoreceptor barrier (nutrient barrier for outer retina) 2. Daily phagocytosis of outer segment discs 3. Vitamin A metabolism 4. Melanin production for high visual acuity 5. Holds back choroidal vasculature from invading subretinal space
43
What is the pathway for the inferior visual world projection onto the retina
Inferior visual world projects to the SUPERIOR retina. Axons from superior retina remain superior in the optic nerve, chiasm, optic radiations (into parietal lobe), and go to the superior bank of the calcarine fissure.
43
A pituitay tumor may push up on the inferior fibers of the chiasm and cause a
Partial heteronomous hemianopsia
44
Name the five basic principles of scotoma identification
1. anopsia is retina or optic nerve 2. hemianopsia is chiasm (bitemporal) or optic tract (homonymous) 3. quadrantanopsia is optic radiations or calcarine fissure 4. macular sparing is unique to occiptal cortex lesions 5. hemianopsias and quadrantanopsias do not produce an APD or alter visual acquity
46
Information from ipsilateral temporal hemiretinas synapse in what LGN layer
2,3,5
47
A partial inferior heteronomous hemianopsia is the result of
craniopharyngioma that impinges on the superior fibers of the chiasm.
48
Information from contralateral nasal hemiretinas synapse in what LGN layer
1,4,6
50
Y ganglion axons synapse in what LGN layer
1,2
51
Optic tract lesions are considered non-localizing because
the loss of left or right visual fields (depending on which optic tract lesioned) can result from optic tract lesions, massive occipital knock out by stroke
52
X ganglion axons synapse in what LGN layer
3, 4,,5, and 6
53
Name the five basic principles of scotoma identification
1. anopsia is retina or optic nerve 2. hemianopsia is chiasm (bitemporal) or optic tract (homonymous) 3. quadrantanopsia is optic radiations or calcarine fissure 4. macular sparing is unique to occiptal cortex lesions 5. hemianopsias and quadrantanopsias do not produce an APD or alter visual acquity
54
What is amblyopia
an eye that is blind but morphologically perfect
55
Information from ipsilateral temporal hemiretinas synapse in what LGN layer
2,3,5
56
Name the three causes of amblyopia
Deprivation (ie cataract, corneal scar) Unequal refraction Misalignment (strabismus)
57
Information from contralateral nasal hemiretinas synapse in what LGN layer
1,4,6
58
What age child can suprress image from weak eye
seven * thus correction must be made before age seven * after correction, give child a patch on dominant eye, keep dominant eye out of focus with glasses or contact lens, dilate dominate eye * Patch, dilate, refractive lens the dominate eye.
59
What age child can suprress image from weak eye
seven * thus correction must be made before age seven * after correction, give child a patch on dominant eye, keep dominant eye out of focus with glasses or contact lens, dilate dominate eye * Patch, dilate, refractive lens the dominate eye.
60
What is the cause of retinal detachements (RD)
tractional forces within the vitreous, or a retinal tear causing the neural retina to separate from the RPE *Photoreceptors begin to die
61
What are unique comments patients say when they have a RD
Floaters, then Firworks/flashes Field defect
62
Do patients with RD have an APD
ONLY if RD present for weeks
63
What does an APD look like with a direct opthalmoscope
Tufts in the retina
64
How painful is an RD
No Pain
65
What is the cause of Retinitis Pigmentosa (RP)
Many causes (abnormal phagocytosis, abnormal outer segment disc proteins, etc)
66
When does RP occur, and what is its phenotype
Congenital NIGHT and peripheral blindness and death of rods>>>central cones
67
Is there an APD associated with RP
NO, not until 50% of retina destroyed
68
Is there pain associated with RP
No
69
What is seen on a fundus exam of a patient with RP
Melanin pigment granules clustered within the retina
70
What is the definitive test for detecting RP
ERG *abnormal a waves
71
What tx is available for pts with RP
Bionic Retinal Implant
72
What is the cause of Chronic (open) angle glaucoma
A clogged trabecular meshwork with the "crap of life" leading to increased intraocular pressure (above 22 mmHg) which pushes on the lamina cribosa and strangles ganglion axons from peripheral retina tunneling centrally OVER time
73
Is open angle glaucoma painful
No
74
Is there an APD with open angle glaucoma
Not until 50% of retina destroyed
75
What scotoma is associated with open angle glaucoma
perisistent tunneling of the visual fields until there is total blindness in OU
76
What is the Tx for open angle glaucoma
Carbonic anhydrase inhibitors- Decrease production of aqueous humor Parasympathomimetics- increase drainage of aqueous humor Trabeculoplasty/trabeculectomy
77
What is the cause of Age Related Macular Degeneration (ARMD)
Precipitation of Drusen (lipid peroxidation) between the choroidal vessels and RPE basal surface beginning in the foveola and spreading laterally (never beyond the maculla) *Drusen kill RPE which keeps photoreceptors alive
78
List the two types of ARMD
dry ARMD | wet ARMD
79
What are the five characteristics of dry ARMD
choroidal vasculature NOT growing down into the area of denerated RPE Not totally blind (peripheral vision remains) Lost ability to read (fixate centrally) No APD No TX
80
What are the characteristics of wet ARMD
choroidal vasculature neovascularizing into the area of degenerated RPE and into the subretinal space Lost ability to read No APD TX available
81
What are the tx options for wet ARMD
Spin retina so macula is now over good RPE, then use prism glasses Transplant RPE from behind iris Avastin to stop revascularization Prevention via antioxidants.
82
What does the scotoma of ARMD look like
Blacked out central vision
83
What is seen on an opthalmascope exam
abnormal foveola, fovea not extending past maculla
84
What is the cause of diabetic retinopathy
Pericytes die>>endothelial cells loose tight jxns and leak lipoproteins>>retinal ischemia>> unstable neovascularization>>bleeding into entire vitreous body>>Total RD * * RD caused by myofibroblast invasion of vitreous following macrophage destruction of RBCs. Myofibroblast pull on retina>>RD * *AKA Proliferative Diabetic Retinopathy d/t noncompliance
85
Is there an APD with diabetic retinopathy
NO
86
What are the three tx for diabetic retinopathy
tight glucose control yearly fundus exam with dye injections (id leaks) Laser to stop revascularization
87
What is the cause of Optic Neuritis
Inflammation in the optic nerve. Associated with MS
88
Y ganglion axons synapse in what LGN layer
1,2
90
X ganglion axons synapse in what LGN layer
3, 4,,5, and 6
92
What is amblyopia
an eye that is blind but morphologically perfect
93
Name the three causes of amblyopia
Deprivation (ie cataract, corneal scar) Unequal refraction Misalignment (strabismus)
94
What are signs of Optic Neuritis
SUDDEN total anopsia in one eye Massive APD Pale/swollen optic disc head
95
What is the tx for optic neuritis
IV steroids | Immunosuppresants if other signs of MS known.
96
What is the cause of Central Retinal Artery Occlusion (CRAO)
An ocular emergency that causes SUDDEN vision total anopsia in one eye d/t DM, HTN, high cholesterol, smoking
97
What are the signs of CRAO
Total blindness in one eye in elderly Massive APD Painless (unless associated with giant cell arteritis) * Cherry red spot at fovea bc choroidal vasculature is intact. * Giant cell artereitis-PAIN in face, scalp, fatigue in holding arms up - Must to temporal artery biopsy within 2 weeks - Steroids and sed rate
98
What is a Retinal Bionic Implant
gas permeablie pad of photosensitive electrodes placed in the subretinal space that senses a photon of light then fires electrical impulses that stimulate adjacent bipolar cells>>improved vision * only in cases where photoreceptors are dying but the retinal synapses are still operating. * Cant read, but sees light vs dark, facial expression, and ambulate.

Nervous system (7 decks)

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