Visual Fields

Question 1

where is our physiological blind spot located?

Answer 1

15 degrees temporal and 1.5 degres below horizontal meridian
(diameter = 5 degrees horizontal and 7 degrees vertical)

Question 2

what is kinetic perimetry?

Answer 2

a target moves from non-seeing to seeing space (shows the area they can see)
the isopter connects the points with the same sensitivity

Question 3

what is static perimetry?

Answer 3

tests different light sensitivities of specific retinal locations on a fixed grid
(30-2 has 6 degree spacing and 10-2 has 2 degree spacing)

Question 4

what is the most critical reliability index?

Answer 4

false positives = makes the VF look better than it actually is and you will miss actual defects

Question 5

what is a depression seen on a VF?

Answer 5

a generalized reduction in retinal sensitivity

Question 6

what is a scotoma?

Answer 6

focal area of reduced sensitivity
absolute = there with maximum stimuli
relative = disappears with brighter stimuli

Question 7

what is the visual pathway?

Answer 7

retinal ganglion cells - optic nerve - optic chiasm - optic tracts - LGN - optic radiations - visual cortex

Question 8

what happens to the optic nerve fibers as they travel posterior to the visual cortex?

Answer 8

they become more organized

Question 9

how is the organization of the fibers different from behind the orbit to near the chiasm?

Answer 9

behind the orbit = nasal fibers have more space and the macular fibers are in temporal half
near chiasm = macular fibers move to center and temporal fibers have more space

Question 10

what is located superior and inferior to the optic chiasm?

Answer 10

superior = hypothalamus and floor of 3rd ventricle
inferior = pituitary gland

Question 11

what is located laterally to the optic chiasm?

Answer 11

ICA and cavernous sinus

Question 12

what happens when the optic chiasm is located anterior to the sella tursica (pre-fixed)?

Answer 12

a tumor will involve the optic tracts first

Question 13

what happens when the optic chiasm is located posterior to the sella tursica (post-fixed)?

Answer 13

a tumor will involve the optic nerves first

Question 14

what is a Von Willebrand’s Knee?

Answer 14

fibers from inferior nasal macula cross into contralateral optic nerve before heading into the optic tract
there is a central defect in the eye with the ON lesion and a superior/temporal defect in the eye with the decussing inferior nasal fibers

Question 15

what type of VF defect is seen at the LGN?

Answer 15

hemianopic (congruous or incongruous) with abruptly sloping borders

Question 16

will a lesion at the LGN have neurologic defects?

Answer 16

yes - they will predominate due to damage of thalamus and/or pyramidal tracts (gross impairment of sensation contralateral to lesion, contralateral hemibody weakness/paralysis)

Question 17

what causes a temporal lobe (inferior optic radiation) defect?

Answer 17

tumor, infarction, epilepsy surgery

Question 18

what are the symptoms for a temporal lobe defect?

Answer 18

visual hallucinations in the affected hemifield, hemiparesis, hemisensory loss and seizures

Question 19

what is the VF defect seen in temporal lobe lesions?

Answer 19

pie in the sky = superior quadrantonopia (usually incongruous)

Question 20

what are the symptoms for a parietal lobe defect?

Answer 20

visual neglect, problems with sensory integration, tactile discrimination, visual-spatial coordination, aphasia, agnosia, and agraphia

Question 21

what is the VF defect seen in parietal lobe lesions?

Answer 21

pie in the floor = inferior quadrantonopia (congruous or incomplete)

Question 22

what causes a visual cortex defect and what will it look like?

Answer 22

cause = vascular (stroke) or traumatic

see absolute congruity with macular sparring (due to dual blood supply)

Question 23

what is the blood supply to the visual cortex?

Answer 23

posterior cerebral artery and middle cerebral artery

Question 24

what forms the posterior cerebral artery?

Answer 24

the right sub-clavian + common carotid artery form the basilar artery

Question 25

what forms the middle cerebral artery?

Answer 25

a terminal branch from the internal carotid artery

Question 26

what are the clinical findings of an optic nerve lesion?

Answer 26

unilateral, invades vertical line/respects horizontal line, complete or partial VA loss, color vision defect and RAPD

Question 27

what are the patterns of VF loss in an optic nerve lesion?

Answer 27

central, central-cecal, arcuate, altitudinal, enlarged blind spot, and diffuse loss

Question 28

what are some causes of an optic nerve lesion?

Answer 28

optic neuritis, trauma, space occupying lesion, NAION, AION, papilledema, nutritional/toxic, glaucoma

Question 29

what are the clinical findings of a chiasmal lesion?

Answer 29

painless/progressive bilateral VA loss, headache, optic atrophy, RAPD, dyschromatopsia, +/- endocrine dysfunction, diplopia

Question 30

what causes a chiasmal lesion?

Answer 30

pituitary adenoma, suprasellar meningioma, ICA aneurysm, optic nerve glioma, trauma/inflammation

Question 31

what causes an anterior chiasmal syndrome?

Answer 31

post-fixed chiasm = compressive disease

Question 32

what are the clinical findings for anterior chiasmal syndrome?

Answer 32

junctional scotoma (due to Von Willebrands knee), ipsilateral APD, +/- diplopia

Question 33

what causes a posterior chiasmal syndrome?

Answer 33

pre-fixed chiasm (macular fibers cross posteriorly in chiasm) = tumor impinges on posterior chiasm and optic tracts

Question 34

what are the clinical findings for posterior chiasmal syndrome?

Answer 34

central bitemporal hemianopic defects (nasal macular fibers)

Question 35

what causes a middle chiasmal syndrome?

Answer 35

suprasellar aneurysm, pituitary gland tumor, suprasellar meningioma and glioma, 3rd ventricle dilation due to obstructive hydrocephalus

Question 36

what is the VF defect seen in middle chiasmal syndrome?

Answer 36

bitemporal heianopia and bitemporal optic atrophy

Question 37

what are some associated findings in chiasmal lesions?

Answer 37

APD, dyschromatopsia, pallor (band like or diffuse) and endocrine dysfunction

Question 38

what causes a post-chiasmal disease? what does the VF look like?

Answer 38

usually due to cardiovascular disease | homonymous (nasal in one eye and temporal in other eye) and congruous

Question 39

what are some causes for optic tract lesions?

Answer 39

tumors, ischemic strokes, aneurysms of superior cerebellar artery or PCA

Question 40

what are some causes for optic radiation lesions?

Answer 40

vascular occlusions, primary/secondary tumors, trauma

Question 41

what does a lesion of the middle cerebral artery in the visual cortex look like?

Answer 41

congruous homonymous hemianopia with macular sparring

Question 42

what does a lesion of the posterior cerebral artery in the visual cortex look like?

Answer 42

congruous homonymous macular defect

Question 43

do lesions in the occipital lobe (visual cortex) have neurologic symptoms?

Answer 43

no (only the parietal and temporal lobes)

Question 44

what is the duel vascular supply to the visual cortex?

Answer 44

vertebrobasilar system (from posterior cerebral artery) and ICA (from middle cerebral artery)