Lecture 2: Afferent Visual System Flashcards
1
Q
If the sympathetic system is involved, the anisocoria will become more apparent in the ___
A
Dark, the sphincter that works in the light is intact
2
Q
Pulfrich’s phenomenon: The pendulum appears to swing closer to the __ eye
A
affected eye, or eye with the neural density filter
3
Q
What is Savino’s Triad?
A
Pupil/Lids/EOM
- If patient has a pathological anisocoria worse in bright light and the abnormal pupil is dilated, then you know the parasympathetic system is affected
- If it is a third nerve palsy causing this issue then you know, based on Savino’s triad that you will also have ptosis and EOM restriction (an eye that is down and out).
4
Q
What does using a bright (halogen) light do?
A
- Go slow enough to give the eye time to release
- Go fast enough to not interrupt the cycle and induce an APD
5
Q
APD may be found in..? (4)
A
- Anterior chamber/vitreous hemes (if retinal detachment or significant pathology present causing heme)
- Optic nerve disorders
- Optic tract issues
- Chiasmal issues
6
Q
APD is never found in..? (4)
A
- Cataract
- Refractive errors
- Lesions posterior to the LGN
- Non-physiologic visual loss
7
Q
Describe the parasympathetic pathway: Light reflex input
A
- Sphincter muscle of the iris - Light reflex input Afferent neurons from retinal ganglion cells to visual cortex
- Via CN II
- 2/3 of the way along the optic tract, some (pupillary axons) leave the tract and enter the brachium of the superior colliculus
- synapse in the pretectal area
- intercalated neurons form the pretectal complex connect to edinger westphal nuclei, bilaterally
- The balance of the axons continue to the LGN
- 2/3 of the way along the optic tract, some (pupillary axons) leave the tract and enter the brachium of the superior colliculus
8
Q
Describe the parasympathetic pathway: parasympathetic outflow
A
- To the sphincter muscle of the iris - parasympathetic outflow
- Parasympathetic fibers originating from the edinger westphal nucleus
- Via oculomotor nerve (CN III) to ciliary ganglion and on to sphincter muscle
- light to one eye allows stimulation of both eyes to constrict
- One eye does not become dilated due to unilateral eye disease
9
Q
Describe the parasympathetic pathway stimulation
A
- Parasympatheticfibers originating at the edinger-westphal nucleus creates the
- Near synkinesis input
- originates from peristriate cortex (area 19) of the occipital lobe at the upper end of the calcarine fissure
- Near synkesis pathway is more ventral than prectal afferent limb of light reflex
- Convergence, acommodation, miosis
- 3% of fibers innervate iris sphincter - represents
- 97% of fibers innervate the ciliary body - represents accommodation
- Convergence, acommodation, miosis
- More ventral location of the pathway is the anatomical bsis for light-near dissociation
- Near synkinesis input
10
Q
Near reflex fibers travel more ___ than the light reflex fibers
A
Ventrally
11
Q
The near reflex travels more ventral than the reflex and its origin is in area __ - __
A
19-20
12
Q
Parasympathetic pathway inhibition: Parasympathetic fibers that originated at the edinger-westphal nucleus is also responsible for..?
A
- Inhibition of the EW nucleus
- Inhibits the sphincter
- Cortical: dilated pupils during seizures
- Spina-reticular: dilated pupils during arousal, excitement
- But, sleep, coma: decline of inhibitory influence over EW, pupils ar emiotic
- Pupils in death: fixed and dialted
- Inhibits the sphincter
13
Q
Describe the sympathetic pathway first order neuron, second order neuron (pre-ganglionic), and third order neuro (post-ganglionic)
A
-
First order neuron
- originates in the posterior hypothalamus, travels down through the brainstem, to the ciliospinal center of budge, approximately from C8-T2
-
Second order neuron (pre-ganglionic)
- leaves spinal cord, enters the paravertebral sympathetic chain, travels through the mediastinum, over the apex of the lung and terminates at the superior cervical ganglion at the base of the skull
-
Third order neuron (post-ganglionic)
- Pupil fibers ascend the carotid artery to enter the skull, in the cavernous sinus it jumps to the CN VI and then CNV1 and the ophthalmic artery
- Passes through the superior orbital fissure
- Fibers on CNV1: muscle of enters the eye dilator via the long posterior ciliary nerves
- Fibers on ophthalmic artery: travel to muller’s muscle of the lids
- The sudomotor and vasomotor fibers to the face travel with external carotid and follow the branches of the facial artery
14
Q
What are the normal pupillary phenomena? (4)
A
-
Physiological Anisocoria
- 20%
- Can vary from day to day and switch sides
-
Pupillary Unrest
- Bilateral, symmetrical, non-rhythmical unrest of less than 1 mm in amplitude
- Aka hippus
-
Near Synkinesis
- If normal light pupil responses are present, can assume near-response normal
-
Psycho-sensory reflex
- sudden noise, startle, pain
- Helpful when demonstrating horner’s syndrome, the dialted eye dilates even more
- Turn out the light and make sudden loud sound
- 2 neural mechanisms occur:
- Active sympathetic discharge
- Stimulates iris dilator
- Inhibition of ocular motor nuclei
- Relaxation of sphincter
- Active sympathetic discharge
15
Q
APD
A
- Extensive vitreous heme/retinal damage can cause APD - RD underlying vitreous heme
- Cataracts never cause an APD
- APD requires asymmetry of light transmission/signal conduction - bilateral glaucomatous damage must be asymmetric to produce R-APD
- APD can occur without VA loss or VF loss - pupillomotor fibers transverse the brachium of the superior colliculus
- VF fibers continuing to LGN may be spared
- APD aka marcus-gunn pupil or RAPD
- optic neuropathy will present with sig APD
- APD is an afferent defect in CN II conduction pathway
- Detecting an APD requires only 1 working pupil - if pt has only one reactive pupil (ex. unilateral pharmacologic dilation), you can still check for an APD in that eye of the other eye
16
Q
What is the best APD testing method?
A
- Magnifier assisted swinging flashlight test
- Transilluminator and 20D lens
- Hold 20D over eye being tested
17
Q
How do we grade APD?
A
- Using a neutral density filter to measure APD
- Hold the filter over the unaffected eye
- Increase log unit until APD no longer seen
- 0.3, 0.6, 0.9 and 1.2 log units
18
Q
Describe APD by reverse
A
19
Q
Pathological Anisocoria: anisocoria ___ in the direction of the paretic muscle
- Spinchinter is affected, worse anisocoria in __ __
- __ system is involved
- Adie’s Tonic pupil - Mydriasis
- __ system is involved
- Dilator affected, worse anisocoria in __ __
- __ system involved
- Horner’s syndrome - Miosis
- __ system involved
A
- Increases
- Bright light
- Parasympathetic
- Dim light
- Sympathetic
20
Q
What are some differential diagnosis for an abnormal pupil that is dilated (parasympathetic system)?
A
21
Q
What are some differentials if you see the abnormal pupil is constricted? (sympathetic system)
A
- Iritis - pain
- Horner’s syndrome - mild ptosis
- Argyll- Robertson pupil - usu bilateral, can have anisocoria
- Long standing Adie’s pupil - initially dilated pupil may constrict over time
- Miotic drops
- “Green cap” medication
22
Q
What can cause Adie’s (Tonic pupil)?
A
- Idiopathic, benign cause of internal ophthalmoplegia
- Lesionmight be in the ciliary ganglion or short posterior ciliary nerves
- May be due to immune reaction, often seen after chickenpox in children
- Early syphilis
- Parvovirus 19
- Neurological lyme disease
23
Q
Descibe Adie’s syndrome (Aka holmes-Adie’s syndrome)
A
- Pupil anomaly plus absent deep tendon reflexes and decreased vibratory sense
24
Q
Adie’s tonic pupil unilateral or bilateral?
A
80% unilateral, tend to become bilateral
25
Adie's are typicall found in (M/F) between the age of __ - \_\_
* Female predilection
* Young adults 20-40 yoa
26
Describe what you could see in a patient with Adie's (Tonic) pupil
* The affected pupil is dialted with poor/absent reaction to light
* Slow constriction after prolonged near effort, and slow re-dilation after near effort (tonic) '
* Initial accommodative paresis resolves after several months
27
How would you test for Adie's pupil?
* If the iris has been deprived of nerve input for a few (5-7) days, it becomes **super-sensitive** to dilute concentrations of cholinergic or adrenergic drops (denervated)
* **Weak pilocarpine (0.125%)** instilled in both eyes
* Affected pupil constricts more than the normal pupil
* Segmental denervation of the iris sphincter visible
* **Light-near dissociation** occurs due to regeneration of the nerves to the ciliary muscle after about 2 months
* **Sign of chornic Adie's pupil**
28
Describe Horner's Syndrome
* Greater anisocoria in **dim illumination**
* ****Transient findings
* Might see increase in pseudo-accommodation in older patients in eye with miosis
* IOP might be lower
* Hemi-facial flush: dilated conjunctival/facial vessels (Harlequinsign)
* Seen on affected side when crying/nursing
* Atropine on affected side reduces flush
* Sympathetic system determines: "curl and color"
* Iris hterochromia in congenital cases: sympathetic input needed for pigment disposition
* Congenital horner's may make child's hair straight on the affected side
* Sympathetic input needed for curly hair
29
How would you test the preganglionic lesion and post ganglion lesion for horner's syndrome?
Spoon test
* **Preganglionic lesion**
* Spoon will catch on skin - no sweat
* **Postganglionic lesion**
* Spoon will glide - sweat present
30
What can cause acquired horner's?
* Beauty shop dolichoectasia
* Vertebral artery dissection
* From cradling a phone
* Heavy backpacks in children
31
Horner's syndrome in children should be evaluated for \_\_\_
* Neuroblastoma
* Most common tumor cause of pediatric horner's syndrome
* 5% arise in the cervial sympathetic chain
32
List the most likely etiologies for Horner's syndrome
* First order neuron
* Second order neuron
* Third order neuron
* **First order neuron**
* Stroke, MS
* MS have been documented with alternating horner's syndrome
* Rare: osteoarthritis with bony spurs
* **Second order neuron**
* ****Tumor, lung carcinoma, metastasis thyroid adenoma
* Pancoast's tumor (NSC) may be associated with pain in arm/scapula
* Children: neuroblastoma, lymphoma, metastasis
* **Third order neuron**
* Headache syndromes
* Cluster, migraine, Raeder's paratrigeminal syndrome
* Internal carotid dissection
* Herpes zoster virus
* Otitis media
* Tolosa-Hun syndrome
* Neck trauma
* Tumor
* Inflammation
* Pituitary adenoma
* **MOST LIKELY:** ipsilateral horner's plus 6th nerve palsy
* aka parkinson's syndrome
* Lesion most likely in cavernous sinus
33
How would you test for horner's syndrome?
* 3 neuron arc of sympathetic system
* 1st order neuron transmitter: acetylcholine
* 2nd order neuron transmitter: acetylcholine
* 3rd order neuron transmitter: nor-epinephrine
34
How does testing with cocaine work with horner's syndrome?
* Cocaine is a **mydriatic** and **dilates normal pupils**
* ****Instill one drop 4-10% cocaine in each eye
* Solution of 4% cocaine blocks the reuptake of nor-epinephrine
* Sympathomimetic effect of cocaine
* Blocks norepinephrine receptors at the myoneural junction, thereby prolonging the action of norepinephrine in the normal eye
* Pupils dilate
* In an **interrupted sympathetic pathway,** there is no nor-epinephrine released at the 3rd order neuron
* The unaffected pupil dilates while the miotic pupil **remains small** and the anisocoria increases
* **cocaine does NOT dilate horner's pupil**
* makes the anisocoria even more evident
* Cocaine stings
* Pt should stay awake
* Cocaine test only **confirms** horner's syndrome and does not differentiate which neuron arc is affected
35
IF the cocaine test is **positive,** what can you do next?
* IF the cocaine test is **positive** (increase anisocoria)
* Instill 2.5% phenylephrine
* Now easily dilates the horner's eye!
36
When should you use apraclonidine instead of cocaine for horner's syndrome?
* 0.5% apraclonidine (instead of cocaine)
* Can use if horner's syndrome is present \> 1 week
* Sympathetic alpha-agonist
* Will make the horner's eye dilate
* Creates anisocoria in the other direction
37
What is paredrine (1% Hydroxy-Amphetamine) used for?
* **Used to determine if the lesion is preganglionic or postganglionic (Horner's)**
* Instill one drop in each eye
* Paredrine creates a sympathomimetic effect
* Causes the _release_ of nor-epinephrine from the nerve endings at the myoneural junction
* Paredrine only works at the **3rd order neuron**, there is no nor-epi at 1st and 2nd order
* Paredrine **dilates** the normal pupil
* Paredrine **dilates** the affected pupil if either the 1st and 2nd order neuron is affected, and only if the 3rd order neuron is intact
* If the 3rd order neuron is affected, the **dilation response will be poor**
38
How does paredrine (Hydroxyamphetamine) work? What if the lesion is in pre-ganglionic? What if the lesion is post-ganglionic?
39
How would you perform a horner's syndrome work up?
40
Describe what an argyll-robertson pupil looks like?
* Small, irregular pupils
* Light - near dissociation
* Usually bilateral
* May be asymmetric
41
What causes argyll-robertson pupil and how would you perform a work-up for this patient?
* Etiology is usu tertiary syphillis
* Diabetes, chronic alcoholism
* Work-up
* Look for findings of syphilis with SL
* Interstitial keratitis (hazy looking eye)
* Chorio-retinitis
* Papillitis
* Uveitis
42
What are some lab testings for argyll-robertson pupils?
* Fluorescent treponemal antiboid absorbent (FTA-ABS)
* Micro-hemagglutination Treponema Pallidum (MHA-TP)
* Rapid plasma reagin (RPR)
* Venereal disease Research Laboratories (VDRL
43
What are 2 types of pupils in coma?
* **Hutinchinson's**
* **Miosis**
44
Describe Hutchinson's Pupil?
* Describes a comatose patient with **unilaterally dilated, poorly reactive pupil**
* Due to ipsilateral expanding, intracranial, supratenorial mass
* Tumor, subdural hematoma
* Downard displacement of hippocampal gyrus and **uncal herniation** with CN III entrapment
45
Describe Miosis
* During early stages of coma: cortical **inhibitory input** to EW diminished and pupils are small and reactive to light
* Remember that the pupils may be constricted due to morphine overdose!
46
For color vision how would you identify congenital loss vs neurological loss?
47
Describe amsler Grid
* Very sensitive to central VF loss
* Use **red-on-black** squre
* More sensitive for more subtle optic neuropathies
* 1 block = 1 degree
* Total of 10 degrees either side and above fixation at 30cm (14 inches)
48
Describe Contrast Sensitiviy testing, what is the gold standard?
* Measure the ability to differentiate between light & dark
* VA of 20/20 may have a potential hidden loss in contrast sensitivity
* Contrast sensitivity measures visual function from low to high spatial frequencies
* Especially important for patients with optic neuritis
* Optic neuritis = inflammation of the optic nerve
* Peli-Robson is the gold standard - can use M&S software
* Considerations
* Day of testing (personal variables)
* Test distance
* Test illumination
* Font/type size and spacing
49
What does the brightness comparison test for?
* Check for unilateral optic neuropathy
* Shine a white light into pt's eye
* Compare **brightness**
* Estimate percentage difference
50
What does the photostress test test for?
* Differentiates retinal disease from optic neuropathy
* Independent of neural pathway
* This test has _measurable_ outcome
* Photostress test **recovery time**
* Procedure
* Determine the best VA in each eye
* Look directly into the light for 10 sec 2-3cm from eye
* Record the time taken to return to best VA
* Normal is less than 30 seconds
* less than 10 seconds is normal
51
What are you looking for when observing the nerve with an ophthalmoscopy?
* Stereo evaluation with a 60, 78, or 90D lens
* Look for
* Swelling of the papilla (unilateral/bilateral elevation)
* Signs of past swelling: **Patton's lines**
* Hemorrhages or dilated nerve vessels
* Drance/splinter hemes or telangiectasia of the nerve
* Collateral/shunt vessels (tumor/CRVO)
* Nevoascularization of the disc (DM)
* **Congestion of the peri-papillary vessels**
* Nerve fiber layer swelling is pathognomonic of a swollen disc
* Pallor, sectoral pallor
* C/D ratio
* Spontaneous venous pulse (SVP)
* Peri-papillary area
* Peri-papillary atrophy
52
53
Optic neuritis
54
Anterior arteritic ischemia neuropathy
55
56
Post-meningitis resolution of optic nerve swelling and resultant optocillliary shunt vessels (aka collaterals)
57
Neovascularizaiton of the optic disc
58
* Optic nerve pallor
59
* Bilateral pallor.. chronicity?
60
Describe VF importance of neurological findings?
* Poor man's MRI
* Screen with very careful confrontation testing/FDT
* Always follow up abnormal findings with formal VF test
* Allunexplained complaints of HA qualify for full formal VF test (NOT screening!)
* Neuro 120pt is available as testing strategy on humphrey
* Not a threshold test (long test)
* Normally just run 24-2 or 30-2 (NOT SITA-FAST)
61
List some neuroimaging
* B-scan ocular ultrasound
* EOM
* Ocular tumors
* Orbital tumors
* Optic nerve
* Papilledema
* Optic disc drusen
* MRI and CT
* MR Angiogram
62
Disc drusen & Drance hemes
63
Buried drusen of the optic nerve
64
How does a B-scan ultrasound work?
65
Describe the wave of a B scan ocular ultrasound
* Frequency of the sound wave is
* The number of oscillations per second
* Inaudible to human ear
* The higher the frequency, the shorter the wavelength
* Shorter wavelength (gain) = improved resolution!
* The medium through which it travels determines the velocity
* Slower through aqueous and vitreous, faster through lens and cornea
* When the wave goes from one density to another, part of the sound is reflected, aka "echo"
* The greater the density difference at the interface, the stronger the echo
66
What are the two types of ultrasound scans?
* A scan
* B scan
67
Describe what information an A-scan provides
* Amplitude modulation scan
* Gives one-dimensional information
* Gives measurements such as axial length or elevation of a mass
68
Melanoma
69
Choroidal melanoma
70
Thyroid eye disease
71
Papilledema
Crescent sign in papilledema: subarachnoid fluid accumulation around optic nerve
72
Describe the basic principles of a CT-scan
* Beam of X rays with detectors and computer algorithm that reconstructs image
* Blunting/attenuation of the ray:
* Dense tissue blocks lots of x-rays
* Grey matter blocks some
* Fluid blocks less
73
Is this image CT or MRI?
* CT Scan
* Dense tissue blocks more x-rays
* Grey matter blocks some
* Fluid blocks less
74
What are the basic principles of MRI?
* Protons oscillate in a magnetic field
* 2 steps:
* The protons absorb energy
* The proteins release energy
* This return to original state is the MRI signal
* This process can occur in 2 directions
* Relaxation **parallel** to the magnetic field takes time (T1)
* Relaxation **perpendicular** to the magnetic field takes time (T2)
75
Describe the difference between MRI T1, T2, and CT
76
Which one is T1, T2, and Flair?
77
Describe T1 and T2 weight sequence/image
78
Describe abnormal findings in T1, T2, and CT
79
What slice orientation is this?
80
What slice orientation is this?
81
What slice orientation is this?
82
What type of scan is this and what are the slice orientation of each?
83
84
* MR angiograms (Nontomographic)
* Single projection with contrast X-ray angiogram
85
86
CT or MRI? Orientation?
* Transverse (left) & CT
* Coronal (right) & MRI
87
What is SPECT/PET?
88
89
* RNFL elevation
* Papilledma
90
What are the RNFL thinning potential causes (OCT)? (11)
* Glaucoma
* Vascular, vitamins
* Inflammatory, infectious
* Autoimmine, allergic
* Metabolic, mass lesions
* Inherited, idiopathic
* Neurodegenerative
* Endocrine, environemtnal
* Senility, stress
91
* OCT ganglion cell complex
92
List 3 evoked potentials
93
* CT
* Transverse-axial
* Tumor
94
* CT
* Transaxial cut
95
* Bright = bleed
* CT
96
* MRI, saggittal, tumor (blood)
97
MS
98
content of lesion? Scan?
99
Contents?
* MRI, Sagittal,
* Tumor, pseudoxanthoma; personality changes
