Visual Fields

hill of vision

3D model of VF sensitivity

kinetic stimuli

• moving target

• fixed size & brightness

• tests non-seeing to seeing

• approach HOV from the sides

static stimuli

• fixed sized target but intensity/brightness varies

• approach HOV from above

60

what is the extent of the superior VF?

75

what is the extent of the inferior VF?

60

what is the extent of the nasal VF?

100

what is the extent of the temporal VF?

120

what is the extent of the binocular VF?

200-220

what is the extent of the VF of both eyes?

absolute defect

no stimulus perceived anywhere in the affected field

relative defect

VF defect changes in size inversely w/ change in size &/or intensity of stimulus

below

on gaze tracking, blinks are recorded as ticks _____ the line

above

on gaze tracking, gaze shifts of more than 5deg are recorded as ticks _____ the line

20%

fixation losses should be less than ____ for reliability

33%

false positives/negatives are flagged when over _____

25%

false positives/negatives should be less than _____

false positives

pt responding that they saw the stimulus when no light stimuli is presented

false negatives

pt responding that they did not see the stimulus when a light brighter than their threshold is shown

central sparing

center of vision is less affected, can get a ring, often starting at the peak of the rods & spreading

arcuate defects

occur in glaucoma when a bundle of ganglion cell axons is damaged at the optic nerve

central

scotoma involving fixation

cecocentral

scotoma involving fixation to the blind spot

paracentral

scotoma involving the area adjacent to fixation

pericentral

scotoma involving the area surrounding fixation

arcuate scotoma & nasal step (Bjerrum’s area)

• coincides w/ anatomy of NFL

• extends from the blind spot

• does not cross the nasal horizontal midline of the VF

• may be isolated w/in Bjerrum’s area

Bjerrums area

A

Bjerrum scotoma

B

paracentral scotoma

C

blind spot

D

Seidel scotoma

E

centrocecal scotoma

F

central scotoma

G

Nasal step

H

homonymous

• defect on the same side of visual space for each eye

• right or left

• lesion posterior to chiasm

heteronymous

• defect on opposite sides of visual space for each eye

• bitemporal or binasal

• lesion usually at the optic chiasm

junctional scotoma

ipsilateral central scotoma & contralateral superior temporal defect, due to optic chiasm damage

improperly placed trial lens, glaucoma, RP

what are possible reasons for a ring scotoma?

33cm

what is the WD for most perimetry?

glaucoma hemifield test

compares pattern deviation probability scores in 5 zones in the upper field compared to the lower field

1. localized

2. respects horizontal meridian

3. often nasal to blind spot

4. almost always detectable w/in central 30deg

what are the classic characteristics of a glaucoma VF defect?

optic neuropathy

• reduced VA

• light brightness

• reduced color perception

• +APD

total deviation

the average of deviations across all test directions, referred to as the mean deviation; affected by cataracts, RE, & things that cause an overall loss in sensitivity

positive

patients who are able to see dimmer stimuli than others of similar age & race will have ______ values for their MD

negative

pts who require brighter stimuli will have ________ MD values

pattern standard deviation

measures irregularity by summing the absolute value of the difference b/t the threshold value for each point & the average VF sensitivity at each point

0

VF w/ age-normal sensitivity at each point will have a PSD of _____

focal, deep

the largest PSD will be registered for _________ VF defects

30

a central 30-2 VF test measures ____ degrees in any direction

10-2

what VF test would you do to test macular issues?

24-2 or 30-2

what VF test would you do to test glaucoma?

wide field

what test would you do to assess neurological damage of the optic tract?

full threshold strategy

• suprathreshold stimulus is presented at each location based on the threshold values from previous points

• intensity is decreased at fixed increments until it is no longer seen, then intensity if increased at fixed increments until it is seen again

• threshold is taken to be = to the intensity of the last stimulus seen at that location

• use smaller steps in intensity & involve more reversals in the direction of presented stimuli

• longer test time

• every retinal location is tested by all possible luminances

FASTPAC

• determines threshold w/ a single reversal using an increment of 3dB

• faster

• underestimates the severity of VF defects

Swedish interactive threshold algorithm (SITA)

• developed for Humphrey perimeter

• uses a complex mathematical model to estimate threshold values for each point based on responses to stimuli presented at that location, as well as info gathered from nearby locations

• full threshold values are still obtained for the 1st 4 points tested & at least 1 reversal from descending to ascending intensity is obtained for each location

• test times in normal individuals are roughly ½ as long as full threshold tests w/ similar or better reproducibility

140

what is the driver’s license requirement of horizontal binocular field?

1. digital VF

2. finger counting

3. tangent screen

what is the preference of VF testing (in order)?

tangent screen

• simple, more sensitive than confrontation fields

• at 1m, tests VF of radius 30deg

• consists of black felt background w/ stitching that indicates 5deg increments, blind spots, & horizontal/vertical/diagonal meridians, central button w/ attached ribbons to set pt distance, wand w/ a white target of various sizes

• kinetic test

• monocular

double

doubling the test distance while also doubling the target size should _______ the field size

exact same sized field

what might malingerers report when the test distance is doubled on a tangent screen test?

frequency doubling technique

• tests to ensure the subject has a statistically normal supra-threshold VF

• standard VF screening test in practices

• assess M-cell functions

• target is a low spatial frequency sinusoidal grating which undergoes high temporal frequency counter-phase flicker

• pt perceives a grating w/ 2x as many light/dark bars as actual

• unaffected by external room light or pupil size

• covers 20deg on all sides of fixation

1. REPEATABLE & RELIABLE

2. abnormal GHT

3. PSD abnormal at P<0.5% level

4. cluster of 3+ on pattern deviation plot abnormal at P<5% & at least 1 at P<0.01%

what are the requirements for suspect of glaucoma (don’t need all)?

a gaze deviation of magnitude greater than or equal to 5deg

in HFA gaze tracking graph, an upward deflection represents _________

60

a 30-2 humphrey VF measures a total horizontal field of what diameter?

pt’s opposite eye is not covered

a pt performs an OD HFA VF w/ no fixation losses, no FP, no FN. the VF is missing a blind spot, what is the likely cause?

optic nerve & macula

a cecocentral scotoma is an area of reduced retinal sensitivity that involves what structures?

left temporal lobe

you observe a bilateral, congruous, right superior quadrantanopia. describe where the lesion is

posterior

relative to an incongruous VF defect, a congruous VF defect is typically ________ in the visual pathway

pre-chiasmal

a unilateral VF defect is most commonly associated with a lesion in what location of the visual pathway?

right parietal lobe

you observe a bilateral, congruous, left inferior quadrantanopia, where is the lesion?

area adjacent to macula

a para-central scotoma represents an area of reduced retinal sensitivity that involves what area of the retina?

relative

a VF defect in which the retinal sensitivity is less than normal at a given location AND which changes w/ a change in stimulus size or intensity is a _______ defect

all that can be seen, finite portion of visual space that an individual can see

visual field is ________ while visual space is ___________

normal

a mild defect occurs in the outer 12 tested locations on FDT, is this normal or abnormal?

60deg

the tangent screen tests a total visual field diameter of ______ horizontally & vertically

Magnocellular

FDT tests for the death of what type of cell?

HFA 30-2

if a pt performs abnormally on an FDT, what would the next test be?

low, high

Magnocellular cells in the LGN are thought to be responsible for ______ contrast, _____ temporal frequency stimuli detection

greater than or equal to 20%

on an HFA threshold VF printout, fixation losses are flagged as significant & the test should be considered invalid at what level?

PSD

the portion of the HFA threshold VF printout that is most commonly used by the doctor to quickly assess pt diagnosis & management is ______

distance of target from subject, actual target size

what factors have an impact on apparent target size?

pt does not understand test, test anxiety, pt is guessing

what are 3 common sources of FPs?

isopter

all locations in the VF w/ identical retinal sensitivity

greater than or equal to 33%

an HFA threshold VF test is flagged w/ an XX if the number of FPs is _____

-6 to +6

a pt taking an FDT VF can typically do so w/o their glasses if their Rx is ________

arcuate, nasal step, enlarged blindspot

what VF defects are associated w/ glaucoma & nerve fiber diseases?

right congruous hemianopsia

describe this VF defect

non-congruous hemianopsia

describe this VF defect

right non-congruous quadranopsia

describe this VF defect

occipital lobe, stroke

describe the location of this lesion & the most probable cause

NFL, glaucoma

describe the location of this lesion & the most probable cause

NFL, glaucoma

describe the location of this lesion & the most probable cause

arcuate

what kind of defect is this?

arcuate

what kind of defect is this?

nasal step

what kind of defect is this