Neuro-ophth Chap 3-4

Neuro-ophth Chaps 3-4:

​DECREASED VISION EVALUATION

by Nolan Adams

​3 Things to Ask on History

• Unilateral or bilateral (make sure a "right eye blindness" is not just a right hemianopsia)

• Time course​ (sudden or gradual)

• ​Associated symptoms (headache, periorbital pain, neurologic symptoms, diplopia, GCA questions)

​Testing for Decreased VIsion

• ​Visual acuity testing

• ​Color vision testing

• ​Pupil exam

• ​Fundus exam

• ​Visual field testing

• ​Other tests...

Multiple Choice

Which is the best routine clinical test to test red-green and blue-yellow color deficiencies?

• Ishihara pseudoisochromatic color plates

• Hardy-Rand-Rittler (HRR) plates

• Farnsworth-Munsell 100-hue test

• Ask patient if colors appear normal to them

​Color vision testing

• Ishihara

  • Better for red-green, not as sensitive, 11 plates

• ​Hardy-Rand-Rittler (HRR)

  • ​Better for blue-yellow and red-green, 24 plates

• ​Farnsworth D-15

  • ​Arrange 15 colored discs

• ​Farnsworth-Munsell 100-hue test

  • ​85 colored discs, most detailed but takes a lot of time so not routine

​This is the control plate everyone should get right

Multiple Choice

A right optic tract lesion will have RAPD in which eye?

• Neither, the optic tract contains both left and right eye fibers

• Right eye because more fibers stay on that side

• Left eye because more fibers cross over at the chiasm

​Pupil exam

• Look for RAPD, remember both eyes can have a problem

• ​53% of fibers cross so optic tract lesion can cause RAPD in opposite eye

• Subjective color intensity can be a stand-in if pupil exam difficult​

​Fundus Exam

• Look for optic nerve pallor/edema

  • ​Pallor shows up 4-6 weeks after axonal damage

  • ​Capillary net may be thin or absent prior to pallor

  • ​Rake defects in RNFL appear at super/inf arcades

• Look for retinal causes of decreased vision

Multiple Choice

Most sensitive and specific confrontational visual field test?

• Red target kinetic testing

• Describe examiner's face

• Finger counting in 4 quadrants

• Bilateral finger movement perception

Multiple Choice

Which perimetry type is kinetic?

• Goldmann

• Humphrey

​Methods of Visual Field Testing

• ​Confrontational fields (kinetic red is best)

• ​Amsler grid testing

• ​Kinetic or static perimetry

Multiple Choice

What Goldmann stimulus size is the Humphrey signal equivalent to?

• Size III

• Size I

• Size V

• Size II

​Adjunct Testing for Decreased Vision

• Contrast sensitivity

• Photostress recovery​ (shine bright light and see when they can read again)

• ​Potential acuity meter (PAM)

• ​Fluorescein angiography

• ​Fundus autofluorescence

• ​OCT (RNFL or Mac or Ganglion Cell Layer)

• ​B-scan

• ​VEP

• ​ERG

Multiple Choice

Is photostress recovery time longer with optic neuropathy or macular disease?

• Optic neuropathy

• Macular disease

• Equal in both

Multiple Choice

What is the OCT RNFL "floor" at which further tissue loss can't be detected?

• 40-50 microns

• 20-30 microns

• 60-70 microns

• There is no floor

​VEP (Visual Evoked Potential) testing

• Electrical signal produced in response to visual stimulus

• Electrodes on scalp over occipital cortex

• Flash reversing checkerboard stimulus

• Obtain P100 wave -- should be 100ms after stimulus, if it occurs too late this may be from demyelination. Optic nerve damage may reduce amplitude.

• Helpful in inarticulate patients and disproving fakers​

​ERG (Electroretinography) testing

• Measure electrical activity in the retina with light stimuli

• Electrodes placed in contact lens

• Full-field ERG stimulates whole retina in different light conditions, capturing rod and cone responses

  • a-wave: photoreceptors

  • b-wave: bipolar cells

  • c-wave: RPE​

• ​Multifocal ERG records and maps ERG signals from 250 locations in bright light conditions, capturing cone responses

Multiple Choice

What kind of test is this?

• Multifocal ERG

• Full field ERG

• Visual evoked potential (VEP)

• Ishihara plate

​ERG vs VEP

• ​VEP = is the visual path intact?

  • ​Messed up by problems anywhere from cornea to occipital cortex

• ​ERG = is the retina intact?

  • ​Full field ERG will change in response to diffuse retinal problems

  • ​Multifocal ERG will change in response to focal pathology

​So you have decreased vision... where?

• ​Anterior segment (cornea, AC, iris, lens)

• ​Vitreous (hemorrhage / vitritis)

• ​Retina

• ​Optic nerve

• ​Optic chiasm

• ​Retrochiasmal lesions

Multiple Choice

Which characteristic is more likely to be true of retinopathy than optic neuropathy?

• Presence of relative afferent pupillary defect (RAPD)

• Cecocentral scotoma

• Metamorphopsias

• Painful

​Retinopathy as cause of decreased vision

• Fundus exam and OCT Mac typically are revealing

• Sneaky diagnoses that masquerade as optic nerve disease:

  • Acute idiopathic blind-spot enlargement (AIBSE)

  • Acute zonal occult outer retinopathy (AZOOR)

  • Multiple evanescent white dot syndrome (MEWDS)

  • Cancer-associated retinopathy (CAR)

  • Melanoma-associated retinopathy (MAR)

  • Nonparaneoplastic autoimmune retinopathy (NpAIR)​

  • ​Cone dystrophy (loss of acuity and color vision)

Multiple Choice

What serum antibody is most specifically associated with Cancer-Associated Retinopathy (CAR)?

• Recoverin

• Enolase

• Arrestin

• Carbonic anhydrase

​CAR vs MAR vs AIR

• All have progressive vision loss, nyctalopia, visual field loss

• CAR - associated with cancer, most commonly small-cell lung CA

  • Recoverin is most specific antibody but only in minority

  • If suspected, do cancer workup

• ​MAR - associated with melanoma, affects rod/bipolar cells

  • ​Visual function may remain stable compared to CAR

• ​NpAIR - 50% association with autoimmune disease

  • ​Variable presentation

  • ​Not associated with recoverin

Multiple Choice

Which visual field defect is ALTITUDINAL?

​Optic Neuropathies

• Papilledema (increased ICP)

• Glaucoma

• Inflammatory

• Vascular (ischemic)

• Compressive/infiltrative

• Hereditary

• Toxic/nutritional

• Traumatic

• Anomalous optic nerve​

Multiple Choice

Patient just got out of spine surgery and is now CF vision in his right eye. His nerve looks like this. Which kind of optic neuropathy is most likely?

• Posterior ischemic optic neuropathy

• Arteritic anterior ischemic optic neuropathy

• Non-arteritic anterior ischemic optic neuropathy

• Optic neuritis from multiple sclerosis

​Ischemic Optic Neuropathy

• Anterior

  • Arteritic anterior ischemic optic neuropathy (AAION) = GCA

  • Non-arteritic anterior ischemic optic neuropathy (NAION)​ = more common vascular injury associated with vascular risk factors, small cup to disc ratio

• ​Posterior ischemic optic neuropathy = typically think perioperative from prone position surgery

  • ​Also could be GCA or similar to NAION

Multiple Choice

What lesion is most likely to give this visual field deficit?

• Craniopharyngioma

• Pituitary adenoma

• Meningioma

• Carotid artery aneurysm

​Optic Chiasm Lesions

• Tumors

• Aneurysms / hemorrhage

• Infections

• Inflammation (sarcoid / MS)

• Trauma

• Radiation damage​

​Tumors of optic chiasm

• ​They will all cause bitemporal hemianopia - can be more superior or inferior depending on tumor location

• ​If located at junction of nerve and chiasm = junctional scotoma

  • ​Loss of vision in affected eye, loss of temporal field in other eye

• ​Pituitary adenoma

  • Most common

  • Will be found earlier if hormone secreting

  • ​Risk of pituitary apoplexy

• ​Parasellar meningioma

  • ​Middle-aged women, may enlarge in pregnancy

​Tumors of optic chiasm

• ​Craniopharyngioma

  • ​More common in children, often arising superiorly in suprasellar space, leading to inferior bitemporal visual field loss

• ​Internal carotid artery aneurysms

  • ​Assymetric syndrome with optic nerve compression on aneurysm side

Multiple Choice

Which of the following is a poor prognostic indicator for pituitary adenomas?

• Mean RNFL thickness <75 microns on OCT

• Slow response to medical therapy with bromocriptine

• Lack of symptom recurrence after 3 months

• Mean Deficit of less than 3 on HVF 24-2

Multiple Choice

Is a lesion at the end of the visual pathway (occipital lobe) more likely to be congruous or incongruous compared to one early in the optic tract?

• Congruous

• Incongruous

• Congruity is not determined by position of lesion

​Retrochiasmal lesions

• Damage to optic tract / LGN / brain lobes

• Contralateral homonymous visual field defects ​(nasal fibers from opposite eye, temporal fibers from ipsilateral eye)

• ​Becomes more congruous as it becomes more posterior because corresponding fibers from both eyes start lining up

• ​Causes:

  • ​Stroke

  • ​Traumatic brain injury

  • ​Tumors

  • ​Aneurysms

  • ​Inflammation

​Optic Tract Lesions

• Will give "bow-tie" atrophy

  • Loss of retinal fibers nasal to the fovea -- aka immediately temporal to nerve and on nasal side of nerve​

• ​RAPD in opposite eye

  • ​More nerve fibers cross than stay

  • ​Nasal retina is more sensitive

Multiple Choice

Where would you find a lesion likely to cause the shown defects?

• Lateral geniculate body

• Optic tract

• Occipital cortex

• Post- highly specific PRP placement

​Lateral Geniculate Body Lesions

• ​Highly organized layered tissue

• ​Lesions can result from ischemia due to PCA or MCA

• ​Defects respect vertical midline but can look very odd

• ​Weird congruous lesions = LGN

​Brain Lobe Lesions

• Temporal lobe = inferior visual fibers = pie in the sky defect

  • Meyer loop is where fibers run

• ​Parietal lobe = superior visual fibers = pie on the floor defect

  • ​Can also lose pursuit pathways and get optokinetic nystagmus

  • ​OKN = can't pursue a target toward the side of the lesion

​Brain Lobe Lesions

• ​Occipital lobe = all fibers = hemianopia with macular sparing

  • 10 deg of visual field in 50% of visual cortex

  • "Temporal crescent" from crossed nasal nerve fibers is in separate region that may be spared when rest of occipital cortex goes down

  • ​PCA stroke = hemianopia with macular sparing

  • ​Hypoperfusion = death of watershed area aka just the macula

  • ​Cerebral blindness can occur with residual pupil function