Visual Fields

visual field

the extent of object space visible while the eye steadily fixates a target; the projection into object space of all parts of the retina responsive to the stimulus being used & not obstructed by facial anatomy

~120deg

what is the binocular VF?

~65deg

what is the extent of the absolute nasal field?

~75deg

what is the extent of the absolute superior field?

~75deg

what is the extent of the absolute inferior field?

~100deg

what is the extent of the absolute temporal field?

~60deg

what is the extent of the relative nasal field?

~60deg

what is the extent of the relative superior field?

~75deg

what is the extent of the relative inferior field?

~100deg

what is the extent of the relative temporal field?

hill of vision

3D model of VF sensitivity, X & Y axes are location & Z axis is sensitivity at that location

kinetic

type of field test where the target comes from the side (approaches HOV from the side), moving target, same illumination & size

static

type of field test where the target is fixed size & intensity of brightness varies, approaches HOV from above

51dB

what is the dimmest stimulus on a field test?

0dB

what is the brightest stimulus on a field test?

28-38dB

what is the foveal threshold?

40dB

__ is typically the least intense stimulus visible by humans

unilateral monocular VF defects

1 eye is affected

bilateral monocular VF defects

• both eyes affected but from different lesions

• same disease, e.g. glaucoma

• different diseases

binocular VF defects

same lesion affecting both eyes

generalized depression

all locations w/in VF show reduced sensitivity (ex: cataract, advanced glaucoma)

depression

an area of decreased sensitivity not necessarily surrounded by normal field (don’t know what the field beyond it looks like)

scotoma

distinct area surrounded by normal field

OS

which eye is shown on the field if the blindspot is on the left side?

OD

which eye is shown on the field if the blindspot is on the right side?

1. Bjerrum’s area

2. coincides w/ anatomy of RNFL

3. extends from blind spot

4. does not cross nasal horizontal midline of VF

5. may be isolated scotoma w/in Bjerrum’s area

describe monocular VF defects: arcuate scotoma & nasal step

superior

inferior notching at the nerve will result in a ______ arcuate defect

altitudinal

2 quadrants of the field affected

temporal

nasal & temporal ganglion cell axons from the macula enter the _____ portion of the ONH

cecocentral or paracentral scotoma

what sort of defect will an issue w/ the nasal & temporal RGCs from the macula cause?

nasal

peripheral nasal ganglion cell axons enter the _____ portion of the optic disc

wedge shaped temporal scotoma extending from blind spot

what sort of defect will an issue with the peripheral nasal ganglion cell axons cause?

1. macula

2. peripheral nasal ganglion cell axons

3. ganglion cell axons temporal to disc

what 3 parts is the RNFL divided into?

superior & inferior

ganglion cell axons temporal to the optic disc (except macular fibes) enter _________ poles

F

T/F: fibers temporal to optic disc cross the horizontal raphe of temporal retina

arcuate defect, paracentral scotoma w/in Bjerrum’s area, nasal step of Ronne

what sort of defect can an issue with the arcuate bundle & peripheral temporal retinal fibers cause?

horizontal, vertical

NFL defects respect the nasal ______ VF meridian but not the _____ meridian

numeric

actual values in dB on the VF printout

grayscale

good plot for pt demonstration on the VF printout

total deviation

difference in dB b/t the pt’s results & age-corrected normal on the VF printout

pattern deviation

• difference from expected based on pt’s own calculated HOV on the VF printout

• highlights significant localized loss & ignored generalized field loss

• probability that a given point is deviant from the average normal values

1. 1/20 points will be below the p<5% level

2. location of points should be random, not clustered

describe a normal pattern deviation

less than 5% of the normal age-corrected population will test the same or lower sensitivity as the patient for that particular point (95% will test higher sensitivity than the patient)

explain what p<5% means

1. peripheral points on the TD are eliminated, except the 1 nasal along the horizontal points

2. adjust the 7th most sensitive point to 0 deviation

explain how the pattern deviation plot is made

mean deviation

• elevation/depression of overall VF compared to normal age-matched reference

• affected by generalized depression & localized defect if large &/or deep

average sensitivity above normal

what does a positive MD mean?

average sensitivity below normal

what does a negative MD mean?

pattern standard deviation

• degree the shape of the patient’s measured HOV departs from the normal age-matched reference

• detects localized defects

• generalized defects have no effect

low

____ PSD: smooth HOV

high

____ PSD: irregular HOV

T

T/F: advanced glaucoma can cause generalized depression in addition to arcuate defects

glaucoma hemifield test (GHT)

• full or SITA threshold 30-2 & 24-2

• pattern deviation plot

• compares 5 upper & lower hemifield in NFL to detect asymmetry

• probability of abnormality in pattern deviation plot

• not necessarily due to glaucoma

1. abnormally high sensitivity

2. general reduction of sensitivity

3. outside normal limits

4. borderline

5. within normal limits

what are the 5 possible outcomes of GHT?

abnormally high sensitivity

• GHT result: overall sensitivity is higher than normal

• at levels <0.5% of norms

• high +MD

• high FP

• supersedes all other messages

generally reduction of sensitivity

• GHT result: overall sensitivity depressed to a degree that occurs in less than 0.5% of normal population

• does not satisfy criteria for outside normal limits

• may appear concurrently w/ borderline message

outside normal limits

GHT result: comparison of upper & lower zone gives a difference greater than that found in 99% of normal population or 2 corresponding zones both depressed greater than that found in 99.5% of normal individuals

borderline

GHT result: any upper zone differs from corresponding lower zone & exceeds that found in 97% of normal individuals

within normal limits

GHT result: none of the other 4 criteria are met

1. new defect

2. deepening of pre-existing defect

3. enlargement of pre-existing defect

4. increased generalized depression

what are the basic guidelines for documenting progressive VF loss?

1. new defect in previously normal area that is typical location for glaucoma

2. cluster of 3 or more points decline in 5dB or greater

3. single point declines 10dB or more

describe a new VF defect

cluster of points decline 10dB or more

describe “deepening of pre-existing defect”

2 points w/in central 15deg or 3 points outside of 15deg decline 10dB or greater

describe “enlargement of pre-existing defect”

decline in MD &/or greater than 3dB at all points not explained by media opacity or pupil size

describe “increased generalized depression”

overall extent of VF damage, proximity of VF damage to fixation point

what 2 criteria is the classification of glaucomatous VF defects based on?

mild defect

• # total points: below 5% level

• % of points on PD plot: <35

• HVF 30-2: <19 points

• HVF 24-2: <13 points

mild defect

• # total points: below 1% level

• % of points on PD plot: <15%

• HVF 30-2: <11 points

• HVF 24-2: <8 points

moderate defect

• # total points: below 5% level

• % of points on PD plot: 25-50%

• HVF 30-2: 19-37

• HVF 24-2: 13-26

moderate defect

• # total points: below 1% level

• % of points on PD plot: 15-30%

• HVF 30-2: 11-23 points

• HVF 24-2: 8-16 points

severe defect

• # total points: below 5% level

• % of points on PD plot: >50%

• HVF 30-2: >37 points

• HVF 24-2: >26 points

severe defect

• # total points: below 1% level

• % of points on PD plot: >30%

• HVF 30-2: >23 points

• HVF 24-2: >16 points

1. MD < -5dB

2. no points w/ sensitivity <20dB in central 5deg

3. <25% of points below 5% level or <15% of points below 1% level

what are the criteria for a mild defect?

mild defect

damage neither extensive nor near fixation

moderate defect

damage may be significant but no profound central damage & no significant central damage in both hemifields

1. MD -5 to -10dB

2. only 1 hemifield w/ points 10-20dB in central 5deg

3. 25-50% below 5% level or 15-30% below 1% level

what are the criteria for a moderate defect?

1. MD > -10dB

2. any point <10dB or points <20dB in both hemifields in central 5deg

3. >50% of points below 5% level or >30% of points below 1% level

what are the criteria for a severe defect?

mild or early stage glaucoma

what stage of glaucoma is present if there is no VF defect?

moderate stage glaucoma

what stage of glaucoma is present if there are glaucomatous VF abnormalities in 1 hemifield & not w/in 5deg of fixation?

severe stage glaucoma

what stage of glaucoma is present if there are glaucomatous VF defects in both hemifields, &/or loss w/in 5deg of fixation in at least 1 hemifield?

1. variability in pt test taking

2. multiple exams required to detect change

3. many schools of through on how much change confirms change

4. estimating rate of progression is challenging

what are some issues facing VF progression analysis?

1. minimum of 3 tests required (2 baseline & 1 f/u)

2. each f/u compared to average thresholds of 2 baseline exams

3. additional f/u compared both to baseline & to 2 most recent f/us

what are the criteria for identifying VF progression?

possible progression

GPA: 3 or more points show deterioration in at least 2 consecutive tests

likely progression

GPA: 3 or more points show deterioration in at least 3 consecutive tests

1. possible progression

2. likely progression

3. no progression detected

what are the 3 results for GPA?

visual field index

• GPA summary report

• summary of measurement of pt’s VF status, expressed as % of normal age-adjusted VF

• weights central vision & removes effect of generalized cataract

VFI rate of progression analysis

• GPA summary report

• trend analysis of pt’s overall VF history

current VF summary

• GPA summary report

• report of current VF including VFI, glaucoma change probability map, & GPA alert

VFI plot

• GPA summary report

• linear regression analysis of VFI values & 3 to 5 yr projection

• minimum of 5 exams over 3 or more years is required

• slope may be positive due to statistical uncertainty or learning effect

VFI bar

• GPA summary report

• graphical depiction of pt’s remaining useful vision at the current VFI value along w/ a 3 to 5 yr projection of the VFI regression line if the current trend continues