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Brain and Behavior > Lectures 25-27: Eye > Flashcards

Lectures 25-27: Eye Flashcards

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1
Q

Elevation mediated by…

A

Sup rectus and inf oblique

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2
Q

Depression mediated by…

A

Inf rectus and sup oblique

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3
Q

Pulling directions of eye muscles are in same plane as…

A

Semicircular canals

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4
Q

Torsional eye movements: which muscle groups control which directions?

A

When eye is abducted, the oblique muscles control torsion; when eye is adducted, the rectus muscles control torsion

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5
Q

Torsion (definintion)

A

Rotating eye movement within the globe

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6
Q

Two causes of IIIrd nerve palsy

A

Uncal herniation or PCOM aneurysm

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7
Q

Describe IIIrd nerve palsy

A

Impaired elevation, depression and adduction (Down and Out); ptosis; enlarged pupil

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8
Q

IVth nerve palsy

A

Gaze of affected eye is up and medial w/ head tilt to unaffected side

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9
Q

VIth nerve palsy

A

Gaze of affected eye cannot abduct

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10
Q

Where does binocular coordination occur in LMNs?

A

Fiber connections in medial longitudinal fasiculus (MLF)

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11
Q

MLF interconnects…

A

The vestibular nuclei, VI, IV, and III

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12
Q

Lesion of abducens nerve

A

Impaired abduction of ipsilateral eye

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13
Q

Lesion of abducens nucleus or PPRF also…

A

Destroys internuclear neurons (which cross and ascend to medial rectus motor neurons in oculomotor nucleus via MLF) –> ipsilateral lateral gaze palsy (inability of patient to look to side of lesion with EITHER eye)

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14
Q

Lesion of MLF…

A

Internuclear opthalmoplegia (INO) (ipsilateral eye cannot adduct, contralateral nystagmus [because brainstem is attempting to maintain conjugate gaze])

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15
Q

Paramedian pontine reticular formation (PPRF)

A

Receives connections from contralateral frontal eye fields and innervates abducens nucleus (so, causes same effect as damage of abducens)

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16
Q

What disease often impacts MLF? Talk about age/diagnosis

A

MS: 1/3 of cases of INO are attributable to MS; 45 yo = unilateral, stroke

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17
Q

Locations of cortical and subcortical control eye movement mechanisms

A

Cortical eye fields: frontal (supplemental eye field and frontal eye field), parietal (parietal and parieto-occipital eye fields); Subcotical regions: superior colliculus, pretectum, RF

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18
Q

Saccadic eye movements (definition and description). For all saccades, cortical outflow is directed to neurons in the…

A

Conjugate eye movements intended to foveate a point of interest, fast and ballistic; superior colliculus

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19
Q

How to make a horizontal saccadic eye movement?

A

PPRF –> abducens –> MLF pathway we learned before PLUS reciprocal inhibitory projections arising from the other abducens nucleus

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20
Q

What is the saccadic gaze center for vertical eye movements? What muscles/nerves?

A

Rostral interstitial nucleus of the MLF (riMLF); IV and III: io, sr, ir

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21
Q

Smooth pursuit eye movements (definition and stimulus)

A

Slow conjugate eye movements used to maintain stable retinal image, stimulus is retinal slip

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22
Q

Pathway for smooth pursuit involves…(network name)

A

Cortico-ponto-cerebellar network

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23
Q

Optokineti nystagmus (phases)

A

Slow component: smooth pursuit (large moving visual targets); Fast component: saccadic eye movement (reflexively resets the eye; DIRECTION NAMED FOR THIS PHASE)

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24
Q

Vestibulo-ocular reflex (VOR) (definition and neuron arc)

A

A compensatory eye movement that maintains visual fixation during head movements; head rotation to the right –> activates the right horizontal canal and inhibits the left horizonal canal –> conjugate gaze to the left (involves excitatory [contralateral to activated canal] and inhibitory [ipsilateral to activated canal] pathway of abducens nucleus)

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25
Q

Caloric testing (theory and pneumonic)

A

Assesses cerebral cortex and brainstem function in unconscious patients, solution different from body temperature will set up convection currents in the fluid w/in the ear, the horizontal (lateral) semicircular canal is tested, then record eye movements; COWS: cold opposite, warm same

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26
Q

Caloric testing (colder)

A

Cold saline in left ear, nystagmus is to the right (opposite direction of the ear)

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27
Q

Caloric testing (warmer)

A

Warm saline in left ear, nystagmus is to the left (same direction of ear)

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28
Q

Vergence eye movements (definition, function, what your eye does)

A

Disconjugate eye movements; maintains fused fixation of a target as viewing distance changes; accommodation and miosis

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29
Q

What fibers interconnect the ciliary muscles and iris muscles?

A

Zonule fibers

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30
Q

Cornea responsible for how much refraction? And what structure does the remaining fraction?

A

2/3; lens

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31
Q

Describe the eye chambers

A

Anterior chamber: b/t cornea and lens filled w/ aqueous humor; Posterior chamber: between zonule fibers and ciliary body, aqueous humor made here by ciliary body; Vitreous body: between retina and lens, filled with vitreous humor

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32
Q

Bipolar cells

A

Link photoreceptors with retinal ganglion cells

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33
Q

Ganglion cells

A

First neuron cell in chain of light transduction

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34
Q

Horizontal cells

A

Horizontal interactions b/t photoreceptor cells (processes in outer plexiform layer)

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35
Q

Amacrine cells

A

Horizontal interactions b/t ganglion cells (processes in inner plexiform layer)

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36
Q

Layers of retina (10) and locations of cell bodies

A

Pigment epithelium, next three layers: photoreceptor cells (outer segment, inner segment, outer nuclear layer [cell bodies]), outer plexiform layer, inner nuclear layer (cell bodies of horizontal cells, bipolar cells, amacrine cells), inner plexiform layer, ganglion cell layer, optic fiber layer, internal limiting membrane

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37
Q

Rods

A

Detect light: low spatial resolution, night/peripheral vision

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38
Q

Cones (and the types w/ colors)

A

Detect color/acuity: high spatial resolution, day/foveal vision; L = red, M = green, S = blue

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39
Q

Relate convergence to acuity

A

HIGH degree of convergence of rods and rod bipolar cells onto retinal ganglion cells; LOW degree of convergence of cones and cone bipolar cells onto retinal ganglion

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40
Q

Fovea

A

Retinal layers become thinner at fovea, reducing barriers to light passage, cone-only region

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41
Q

What’s cool about the structure of the optic nerve?

A

It’s CNS, so it’s covered with dura right up to the retina w/ central retina vessels running through

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42
Q

Blind spot is located in the _________ portion of the visual field

A

Temporal

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43
Q

Binocular visual field (definition) is flanked by the ________ _________

A

Area of the world seen by both eyes; monocular crescents

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44
Q

What happens at the optic chiasm? Which ones cross? So what happens?

A

Some of the fibers of the optic nerve cross; nasal retinal fibers (NOT temporal retinal fibers); right optic tract carries left visual field, left optic tract carries right visual field

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45
Q

Cut optic nerve…

A

Monocular blindness

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46
Q

Damage optic chiasm (in saggital plane)…why?

A

BiTEMPORAL hemianopia (while the nasal retinal fibers are cut, they carry the temporal visual field)

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47
Q

Where does optic tract travel to? How many cell layers and information? Does mixing of information from different eyes happen?

A

Lateral geniculate nucleus; 6; parvocellular layers (4) = cones, magoncellular layers (2) = rods; NO

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48
Q

Cut optic tract or LGN…

A

Homonymous hemianopia

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49
Q

What visual field quadrant is carried by Meyer’s loops? Damage (optic radiations temporal lobe)?

A

Upper quadrant = homonynous superior quadrant hemianopia

50
Q

Cut optic radiations (parietal lobe)

A

Homonymous inferior quadrant hemianopia

51
Q

Superior visual field where in respect to calcarine fissure?

A

Inferior

52
Q

Foveal vision maps to where in respect to occipital cortex?

A

Occipital pole

53
Q

Damage to primary visual cortex…

A

Homonymous hemianopia

54
Q

Damage to primary visual cortex further back…Why?

A

Homonymous hemianopia with macular sparing; due to magnificant factor (must damage a lot of occipital pole) and to blood supply

55
Q

What two muscles control pupillary light reflexes and function

A

Sphincter pupillae: constricts, para; Dilator pupillae: widens, sympa

56
Q

Steps of direct pupillary light reflex

A

Afferent: 1. Light to eye; 2. Optic nerve, chiasm, tract; 3. Midbrain pretectum. Efferent: 4. Edinger-Westphal nucleus, 5. CN III to ciliary ganglion; 6. IPSILATERAL sphincter muscle contracts

57
Q

Steps of consensual pupillary light reflex

A

Afferent: 1. Light to eye; 2. Optic nerve, chiasm, tract; 3. Midbrain pretectum. Efferent: 4. CONTRALTERAL Edinger-Westphal nucleus via posterior commissure, 5. CN III to ciliary ganglion; 6. CONTRALTERAL sphincter muscle contracts

58
Q

What cells project to which brain structures (3) to control light-dependent biological clock. Name function of each structure.

A

Photosensitive retinal ganglion cells project to the hypothalamus (suprachiasmatic nucleus = circadian rhythm), pineal gland = melatonin, and pretectal nucleus = pupillary light reflexes

59
Q

What determines absorption in eye

A

Length of time drug stays in cul-de-sac

60
Q

What are the two themes of distribution for the eye?

A

Systemic distribution: via nasal mucosa; Ocular distribution: via transcorneal/transconjunctival route

61
Q

What determines eye metabolism? What does the metabolism?

A

Tear and tissue proteins, diffusion across cornea/conjunctiva; enzymes in eye and hepatic

62
Q

Elimination in the eye

A

Nasolacrimal drainage –> bloodstream –> liver (note: avoids first pass metabolism that you have for oral meds)

63
Q

Miosis

A

Constriction of pupils

64
Q

Mydriasis

A

Dilation of pupils

65
Q

Describe iris muscles

A

Sphincter/inner circular muscle = para; Outer radial muscle = sympa

66
Q

What characterizes glaucoma

A

Elevated intraocular pressure (presses backward damaging optic nerve –> progressive retinal ganglion cell axon loss)

67
Q

Types of glaucoma and presentation. What makes the angle?

A

Open-angle glaucoma (allows aqueous humor to circulate that is usually found on exam) and closed-angle glaucoma (emergency, no fluid can circulate to cornea, major increase in intraocular pressure that presents with pain, acute visual loss, erythema/edema); lens and iris makes angle

68
Q

How do we treat closed angle glaucoma?

A

Lasor irodotomy: drills hole between iris and ciliary body to allow for drainage

69
Q

Glaucoma is diagnosed with…(3)

A

Fundoscopic exam: cupping (enlarged, hollowed out appearance of optic nerve), visual field testing, intraocular pressure

70
Q

Ciliary body consists of…

A

Ciliary muscles (2) and ciliary epithelium

71
Q

Accommodation is mediated by __________ stimulation causing which muscle to contract? Define cyclospasm and cycloplegia

A

Parasympathetic; ciliary muscle; cyclospasm = severe muscle contraction and cycloplegia = no accommodation

72
Q

What allows the aqueous humor to flow out? (2 methods)

A
  1. Para stimulation –> tension of trabecular meshwork –> opening of pres allowing flow through Canal of Schlemm and trabecular meshwork; 2. Uveoscleral outflow pathway: aqueous humor can also flow through ciliary muscles into suprachoroidal space
73
Q

What promotes aqueous humor secretion

A

Sympathetic stimulation via beta receptors

74
Q

How to treat glaucoma?

A
  1. Increase outflow (uveoscleral/canal of Schlemm) or 2. Decrease production
75
Q

What is the first line therapy (example) for treatment of glaucoma, SEs.

A

Prostaglandin agonists (Latanoprost) which increase aqueous humor outflow via uveoscleral pathway; SEs: blurred vision, irritation, iris color change, keratitis

76
Q

What receptor antagonist can be used to treat glaucoma (example)? Mechanism, SEs and special considerations (2)

A

Beta receptor antagonist (Timolol); decrease aqueous humor production; SEs: eye-related AND cardiovascular (bradycardia, hypotension), respiratory (cough, dyspnea); don’t give to patients w/ respiratory disease and CYP2D6 metabolism

77
Q

What receptor agonist can be used to treat glaucoma (example)? Mechanism, SEs

A

Alpha2 agonist (Brimonidine); decrease aqueous humor production via pre (less NE) and post synaptic (less cAMP) alpha2 receptors; SEs: eye-related AND cardio: hypotension

78
Q

Carbonic anhydrase inhibitors example? Mechanism, SEs

A

Dorzolamide; HCO3- is secreted from blood into aqueous humor, inhibited by CA inhibitor, decreasing aqueous humor production, SEs: eye-related AND metabolic acidosis via CA inhibition in the kidney (HCO3- in lumen not changed into CO2, H2O to be reabsorbed)

79
Q

Cholinergic agonist: 2 examples? Mechanism, SEs

A

Carbachol, Pilocarpine; muscarinic agonist: ciliary muscle contraction helps outflow; SEs: eye-related

80
Q

Name two corneal disorders

A

Corneal abrasion (visualized with flourescent dye) and corneal ulcer (infection from an abrasion)

81
Q

What is presbyopia?

A

Loss of accomodation of the eye due to weakening of the zonules.

82
Q

A cataract is the most common disorder of the…what happens?

A

Lens; becomes cloudy and obstruct vision

83
Q

During cataract surgery, what is put in the eye?

A

Intraocular lens (lens implant)

84
Q

What is the second most common cause of visual loss in elderly?

A

Glaucoma

85
Q

What is glaucoma?

A

Optic nerve damage associated with visual field defects usally associated with high intraocular pressure

86
Q

What kind of vision loss happens with glaucoma?

A

Loss of peripheral vision

87
Q

Glaucoma risk factors (6)

A

Elderly, African/Hispanic Americans, elevated with IOP, family history, diabetics, high myopia

88
Q

What to check for when looking for glaucoma (3)

A

Eye pressure, visual field test, optic nerve damage

89
Q

How do we test for optic nerve damage?

A

Enlarged cup in optic disc

90
Q

Treatment for open angle glaucoma

A

Medications

91
Q

Treatment for closed angle glaucoma and risk groups

A

Laser iridotomy; small eyes: Asians, females

92
Q

What is the most common cause of elderly visual loss?

A

Age-related macular degeneration

93
Q

What kind of vision loss happens with ARMD?

A

Central vision loss

94
Q

ARMD risk factors (5)

A

Advanced age, fair skin/eyes, family history, smoking and heart disease

95
Q

What causes dry ARMD?

A

Yellow deposits scattered throughout retina with gradual visual loss

96
Q

What is the difference between dry and wet ARMD?

A

Fluid/bleeding beneath retina with sudden loss of vision; permanent damage

97
Q

T/F: Diet has been shown to prevent ARMD

A

True! A diet rich in fruit and vegetables

98
Q

Diabetic retinopathy is the __th leading cause of blindness in elderly Americans. How about working-age Americans?

A

4th; leading cause

99
Q

What kind of vision loss happens with diabetic retinopathy?

A

Blurry vision with missing patches

100
Q

T/F: Diabetic retinopathy cannot be prevented

A

False! Important for patient to work with doctors to screen for diabetic retinopathy

101
Q

Increased blood glucose damages what in the eye?

A

Retinal capillaries

102
Q

What are four pathological fundoscopic finding in diabetic retinopathy?

A

Microaneurysms (like little red dots), hemorrhages, cotton wool spots (ischemia), and hard exudates (later stage)

103
Q

Three stages of diabetic retinopathy

A

Non-proliferative, pre-proliferatie, proliferative (neovascularization that causes vision loss)

104
Q

What causes neovascularizastion? What is the reatment?

A

VEGF, lazer damaging of retina to regress neovascularization

105
Q

Where does the optic nerve become myelinated? Is it covered by meninges?

A

After it exits the optic disc; yes

106
Q

What is optic neuritis (ON)? Pathogenesis

A

Inflammation of the optic nerve; demyelination of nerve

107
Q

If optic neuritis occurs alone it’s called ________

A

Idiopathic

108
Q

What is the most common optic neuritis association? What are some others (2)

A

MS (first clinical sign); sarcoidosis and infections

109
Q

Symptom onset of ON and symptoms (4). Recovery?

A

Acute, loss of visual acuity, color, field and afferent pupillary defect; vast majority

110
Q

T/F: ON always presents with a swollen nerve

A

False! Hard to detect with a fundoscopic exam

111
Q

If someone has ON, what should be done?

A

Get an MRI to assess for MS

112
Q

What is the difference between bilateral optic disc edema (two swollen discs) and papilledema?

A

Papilledema requires increased ICP (so, not all bilateral disc edemas cause papilledema)

113
Q

What should you do if you find papilledema?

A

Scan them!

114
Q

Reflexes of sphincter muscle

A

Light and near reflex

115
Q

Difference in pupil size called? Can be…

A

Anisocoria; pathologic and physiologic

116
Q

If one eye sees less light than the other, this is called…

A

Relative Afferent Pupillary Defect (RAPD)

117
Q

RAPD can be caused by…(4)

A

Optic neuropathy, chiasmal/tract lesion, retinal damage, blindness

118
Q

What is (Holmes-Adie) Tonic Pupil? Who tends to get this and how does it present? What is damaged?

A

Idiopathic disorder where one pupil (the abnormal one) is larger and reacts poorly to light/accommodation; young women often complain of difficulty reading; parasympathetic fibers to pupil

119
Q

Argyll Robertson Pupils and number one and two cause

A

Miotic pupils w/ absence of pupillary light response but retention of near response; neurosyphilis and diabetes

120
Q

IIIrd nerve palsy tends to effect which fibers first? What does this look like? What can cause this?

A

Pupillary fibers; affected pupil is mydriatic; uncal herniation/PCOM aneurysm

121
Q

What is Horner syndrome? It causes…

A

Oculosympathetic paralysis; miosis of affected pupil and ptosis

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