Visual Fields

120

what is the binocular VF?

kinetic

• moving target VF

• fixed size & brightness

• non-seeing to seeing

• approaches HOV from the sides

isopter

limits of retinal sensitivity to a specific test target

static

• fixed size target

• intensity or brightness varies

• approaches HOV from above

40

___dB is typically the least intense stimulus visible by humans

pt is probably trigger happy bc they cannot see above ~40dB

what does it tell you if the pt is getting VF values above 40dB?

III

what size stimulus is typically used for VF testing?

>0.5 sec, a head turn

typically when VF testing, a stimulus of 200ms in duration is used, if you use a stimulus of _____, it might cause _____

screening

testing strategy to make sure that the subject has at least a “statistically normal” VF; usually no attempt to measure/quantify performance

threshold

testing strategy to find the weakest stimulus seen 50% of the time; measures or quantifies performance at some or all locations & makes a “frequency of seeing” curve

frequency of seeing curve

probability of seeing stimuli over range of intensities

absolute defect

no stimulus perceived in the affected field

relative defect

VF defect changes in size inversely w/ change in size &/or intensity of stimulus (less than normal sensitivity but some stimulus is detected)

SITA - standard

• threshold strategy

• 4 then 2dB steps

• initial crossing of threshold, then reversal in 2dB steps to final crossing

SITA - fast

• threshold strategy

• single crossing

• higher intratest variability

SITA

• complex mathematical model that uses different step sizes & intelligent decision rules

• ½ the time w/ no loss of reproducibility or diagnostic info

• high accuracy & less variability

• based on age-corrected values in normal & glaucomatous populations, frequency of seeing curves around threshold values, correlations b/t adjacent test points

• probability function is adjusted continuously as the test proceeds

HFA3 SITA-Faster

• 35% faster than SITA fast

• tested in both normal & glaucoma pts

• reduced dead time b/t stimuli & eliminates blind spot tracking & false negative testing

• uses a gaze tracker

• maybe poor sensitivity & specificity so not used much

54, 76

a 24-2 tests ___ points w/in 24deg while a 30-2 tests ___ points w/in 30deg

68

a 10-2 tests ____ points w/in the central 10deg

1. direct observation

2. gaze tracking

3. fixation losses (Heijl-Krakau blind spot monitoring)

what are the 3 ways to monitor fixation on a VF?

gaze deviation

an upward deflection on the gaze tracker indicates what?

blink or eye closure

a downward deflection on the gaze tracker indicates what?

fixation losses (Heijl-Krakau blind spot monitor)

# of times pt responded to stimulus that was presented in the presumed blind spot location

1. loss of fixation

2. blind spot incorrectly plotted

3. trigger happy

4. head tilt

what can cause a fixation loss?

false positive

• # of times pt responds positively when pt responses are not expected

• can be caused by: trigger happy or lack of understanding, anxiety

false negatives

• # of times pt fails to respond when a distinctly visible stimulus (9dB or less) is presented

• presented only at test point locations where threshold sensitivity has already been measured

• can be caused by: FATIGUE, slow rxn time, hysteria/malingering, disease

decreased reproducibility of glaucomatous VF

what do false negatives reflect in a glaucoma pt?

20, 15, 15-30

suspect reliability issues in normal pts if: fixation losses are >__%, false positives are >___%, and/or false negatives are >___%

unilateral

_______ VF defect: 1 eye is affected

bilateral

______ VF defect: both eyes are affected but due to different lesions (same or different disease)

binocular

______ VF defect: the same lesion is affecting both eyes

central

scotoma that involves fixation

cecocentral

scotoma that involves fixation to the blind spot

paracentral

scotoma that is adjacent to fixation

arcuate scotoma & nasal step

• Bjerrum’s area

• coincides w/ RNFL anatomy

• extends from the blind spot

• does not cross nasal horizontal midline of VF

• can be an isolated scotoma w/in Bjerrum’s

altitudinal

VF defects that respect the horizontal meridian

heteronymous

• VF defect in opposite sides of visual space for each eye

• bitemporal or binasal

• lesion usually at the chiasm

homonymous

• VF defect in same side of visual space for each eye

• right vs left

• lesion is posterior to the chiasm

quadrantanopia

VF defect that respects the vertical & horizontal meridian

hemianopia

VF defect that affects 2 adjacent quadrants & respects the vertical meridian

F

T/F: you have to specify heteronymous in the VF defect description

complete

no vision at all in the affected half of the VF

incomplete

partial vision in affected half of the visual field

congruous

• VF coincide when superimposed

• more similar by angle of defect border & depth of defect

congruous

ischemic events will usually cause more _______ VF defects

incongruous

compressive lesions like tumors will usually cause more _______ VF defects

posterior

more ________ lesions in the visual pathway usually cause more congruous defects

bitemporal hemianopia

right complete homonymous hemianopia w/ macular splitting

left incomplete congruous homonymous hemianopia

OD double arcuate VF defect, inferior > superior w/ inferior nasal step

left incomplete incongruous homonymous hemianopia

temporal

macular ganglion cells enter the _______ portion of the ONH

nasal

the peripheral nasal ganglion cells enter the _______ portion of the ONH

superior & inferior

the ganglion cell axons temporal to the disc (other than macular fibers) enter the __________ portion of the ONH

1. reduced VA

2. light brightness diminished

3. reduced color perception

4. RAPD (if unilateral or asymmetric)

5. VF defect

what are some s/sx of optic neuropathy?

optic neuritis, neuroretinitis, toxic & nutritional optic neuropathies, compressive lesions, optic pit w/ central serous choroidopathy

what are some pathologies that might cause a cecocentral scotoma?

papilledema, peripapillary atrophy (POHS, posterior staphyloma, high myopia)

what are some pathologies that might cause an enlarged blind spot (Seidel scotoma)?

AION, glaucoma, BRAO, RD

what are some pathologies that might cause an altitudinal VF defect?

ipsilateral

temporal fibers from nasal VF pass directly through the optic chiasm to the _______ optic tract

contralateral

nasal fibers from temporal VF pass through the optic chiasm to the ______ optic tract

posteriorly

superior nasal fibers from the inferior VF decussate ________ in the optic chiasm

anteriorly

inferior nasal fibers from the superior VF decussate _________ in the optic chiasm

junctional scotoma

• lesion at the anterior chiasm & posterior optic nerve

• VF defect: unilateral temporal or ipsilateral central scotoma & contralateral superior temporal defect

fixation

where do chiasmal VF defects originate?

vertical

chiasmal VF defects respect which meridian?

T

T/F: an optic tract lesion may produce a greater VF defect in the contralateral eye & a mild RAPD compared w/ a chiasmal lesion

ONH drusen, tilted optic discs, ON hypoplasia

what are some pathologies that can cause pseudo-bitemporal hemianopia?

T

T/F: when the optic tract is damaged, 6-9mo later optic atrophy can be seen at the disc

eye w/ the temporal VF defect

if an optic tract lesion causes an APD, which eye will it be in?

bow tie/band optic atrophy

• occurs w/ damage to crossing fibers

• lesion in the optic chiasm or optic tract

• retrograde atrophy w/ cell death

decreased pain sensation, contralateral body weakness

what are some systemic s/sx that may accompany VF defects w/ damage to the LGN?

F

T/F: there will be an APD w/ an LGN lesion

anterior choroidal artery & posterior choroidal artery

what supplies blood to the LGN?

keyhole defect/sector-sparing homonymous hemianopia

• VF defect that can result from an anterior choroidal artery occlusion

• respects the vertical meridian

homonymous horizontal sectoranopia (incomplete hemianopia)

• VF defect that can result from a posterior choroidal artery occlusion

• respects the vertical meridian

• points to fixation

Meyer’s loop

formed by the inferior fibers from superior VF coursing anteriorly around the lateral ventricle from LGN to the temporal lobe

incomplete homonymous hemianopia or superior homonymous quadrantanopia

what type of VF defects can result from a lesion to the optic radiations in the temporal lobe?

unusual taste/smell, hallucinations, seizures, dysphasia, anomia

what are some systemic s/sx that can accompany VF defects from a temporal lobe lesion?

posteriorly

superior fibers from the inferior VF course _________ from the LGN into the parietal lobe

complete or incomplete homonymous hemianopia

what VF defect is created from a lesion to the optic radiations in the parietal lobe?

inferior

if the VF defect from a lesion to the parietal lobe optic radiations is incomplete, which side is denser?

seizures, loss of tactile discrimination, hypotonia, ataxia

what are some systemic s/sx that can accompany VF defects seen in parietal lobe lesions?

altitudinal

if there is a quadrantanopia from an occipital lobe lesion, it may be _________ if bilateral

1. there is dual arterial supply to the macular cortex

2. macular fibers project to both hemispheres

what are the theories behind macular sparing vs macular splitting in occipital lobe lesions?

the parietal lobe contains visual association area for directing smooth eye movements

explain why OKR and OKN are disrupted w/ a parietal lobe lesion?

towards

a disruption in OKR and OKN will occur when the target moves ______ the side of the parietal lobe lesion

normal

describe the OKN with an occipital lobe lesion

cecocentral scotoma

enlarged blindspot

altitudinal VF defect

junctional scotoma

bitemporal hemianopia

pseudo-bitemporal hemianopia

left incomplete incongruous homonymous hemianopia

sector-sparing homonymous hemianopia (keyhole defect)

homonymous horizontal sectoranopia

right incongruous homonymous superior quadrantanopia

left incomplete homonymous quadrantanopia, denser inferior (incomplete left inferior quadrantanopia)

left incomplete congruous homonymous hemianopia w/ macular sparing