Visual Fields Flashcards
where is our physiological blind spot located?
15 degrees temporal and 1.5 degres below horizontal meridian
(diameter = 5 degrees horizontal and 7 degrees vertical)
what is kinetic perimetry?
a target moves from non-seeing to seeing space (shows the area they can see)
the isopter connects the points with the same sensitivity
what is static perimetry?
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)
what is the most critical reliability index?
false positives = makes the VF look better than it actually is and you will miss actual defects
what is a depression seen on a VF?
a generalized reduction in retinal sensitivity
what is a scotoma?
focal area of reduced sensitivity
absolute = there with maximum stimuli
relative = disappears with brighter stimuli
what is the visual pathway?
retinal ganglion cells - optic nerve - optic chiasm - optic tracts - LGN - optic radiations - visual cortex
what happens to the optic nerve fibers as they travel posterior to the visual cortex?
they become more organized
how is the organization of the fibers different from behind the orbit to near the chiasm?
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
what is located superior and inferior to the optic chiasm?
superior = hypothalamus and floor of 3rd ventricle inferior = pituitary gland
what is located laterally to the optic chiasm?
ICA and cavernous sinus
what happens when the optic chiasm is located anterior to the sella tursica (pre-fixed)?
a tumor will involve the optic tracts first
what happens when the optic chiasm is located posterior to the sella tursica (post-fixed)?
a tumor will involve the optic nerves first
what is a Von Willebrand’s Knee?
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
what type of VF defect is seen at the LGN?
hemianopic (congruous or incongruous) with abruptly sloping borders
will a lesion at the LGN have neurologic defects?
yes - they will predominate due to damage of thalamus and/or pyramidal tracts (gross impairment of sensation contralateral to lesion, contralateral hemibody weakness/paralysis)
what causes a temporal lobe (inferior optic radiation) defect?
tumor, infarction, epilepsy surgery
what are the symptoms for a temporal lobe defect?
visual hallucinations in the affected hemifield, hemiparesis, hemisensory loss and seizures
what is the VF defect seen in temporal lobe lesions?
pie in the sky = superior quadrantonopia (usually incongruous)
what are the symptoms for a parietal lobe defect?
visual neglect, problems with sensory integration, tactile discrimination, visual-spatial coordination, aphasia, agnosia, and agraphia
what is the VF defect seen in parietal lobe lesions?
pie in the floor = inferior quadrantonopia (congruous or incomplete)
what causes a visual cortex defect and what will it look like?
cause = vascular (stroke) or traumatic
see absolute congruity with macular sparring (due to dual blood supply)
what is the blood supply to the visual cortex?
posterior cerebral artery and middle cerebral artery
what forms the posterior cerebral artery?
the right sub-clavian + common carotid artery form the basilar artery
what forms the middle cerebral artery?
a terminal branch from the internal carotid artery
what are the clinical findings of an optic nerve lesion?
unilateral, invades vertical line/respects horizontal line, complete or partial VA loss, color vision defect and RAPD
what are the patterns of VF loss in an optic nerve lesion?
central, central-cecal, arcuate, altitudinal, enlarged blind spot, and diffuse loss
what are some causes of an optic nerve lesion?
optic neuritis, trauma, space occupying lesion, NAION, AION, papilledema, nutritional/toxic, glaucoma
what are the clinical findings of a chiasmal lesion?
painless/progressive bilateral VA loss, headache, optic atrophy, RAPD, dyschromatopsia, +/- endocrine dysfunction, diplopia
what causes a chiasmal lesion?
pituitary adenoma, suprasellar meningioma, ICA aneurysm, optic nerve glioma, trauma/inflammation
what causes an anterior chiasmal syndrome?
post-fixed chiasm = compressive disease
what are the clinical findings for anterior chiasmal syndrome?
junctional scotoma (due to Von Willebrands knee), ipsilateral APD, +/- diplopia
what causes a posterior chiasmal syndrome?
pre-fixed chiasm (macular fibers cross posteriorly in chiasm) = tumor impinges on posterior chiasm and optic tracts
what are the clinical findings for posterior chiasmal syndrome?
central bitemporal hemianopic defects (nasal macular fibers)
what causes a middle chiasmal syndrome?
suprasellar aneurysm, pituitary gland tumor, suprasellar meningioma and glioma, 3rd ventricle dilation due to obstructive hydrocephalus
what is the VF defect seen in middle chiasmal syndrome?
bitemporal heianopia and bitemporal optic atrophy
what are some associated findings in chiasmal lesions?
APD, dyschromatopsia, pallor (band like or diffuse) and endocrine dysfunction
what causes a post-chiasmal disease? what does the VF look like?
usually due to cardiovascular disease
homonymous (nasal in one eye and temporal in other eye) and congruous
what are some causes for optic tract lesions?
tumors, ischemic strokes, aneurysms of superior cerebellar artery or PCA
what are some causes for optic radiation lesions?
vascular occlusions, primary/secondary tumors, trauma
what does a lesion of the middle cerebral artery in the visual cortex look like?
congruous homonymous hemianopia with macular sparring
what does a lesion of the posterior cerebral artery in the visual cortex look like?
congruous homonymous macular defect
do lesions in the occipital lobe (visual cortex) have neurologic symptoms?
no (only the parietal and temporal lobes)
what is the duel vascular supply to the visual cortex?
vertebrobasilar system (from posterior cerebral artery) and ICA (from middle cerebral artery)
