Visual field evaluation ESCRS - PowerPoint Presentation

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Visual field evaluation

ESCRS

Dr Fiona Rowe

University of Liverpool

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Goals

Visual pathway anatomy

Methods of

perimetry

use for Humphrey visual field analyser,

Goldmann

perimeter, Octopus 900 perimeter

Visual field printout options

Interpretation of results using statistical packages provided by the perimeter systems

Discussion of the ocular symptoms and signs associated with lesions along the various parts of the visual pathway

Possible localisation of lesion according to type of visual field defect plotted

Artefacts of visual field defects and their avoidance.

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Visual pathway and topography

Retina

Optic disc

Optic nerve

Optic chiasm

Optic tract

Lateral geniculate body

Optic radiations

Visual cortex

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Retina

Papillomacular bundle – fovea

Nasal retina

Superior retina

Inferior retina

Temporal retina

Central fibres develop first

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Optic disc

Representation of retinal nerve fibres

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Optic nerve

Fibres become myelinatedRepresentation of retinal nerve fibres

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Optic chiasm

13mm wideSurrounded by pituitary gland, third ventricle, thalamus, cavernous sinusCrossing of nasal retinal fibresSuperior (above), inferior (below), macular (central)

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Optic tract

Sweep laterally from chiasm around hypothalamus and ventral portion of midbrain

Regroup of fibres – inexact pairing

Ipsilateral temporal and contralateral nasal retinal fibres

Superior (superomedially), inferior (inferolaterally)

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Lateral Geniculate Body

Diencephalon, midbrainFirst synapse of retinal nerve fibresRotate through 90 degreesSuperior (medial), inferior (lateral)6 layersMacular fibres in all 6 layersIpsilateral temporal fibres; 2, 3, 5Contralateral nasal fibres; 1, 4, 6

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Optic radiations

90 degree realignment of nerve fibresSuperior (above), inferior (below)3 groupsUpper and central pass directly to visual cortex via posterior temporal and parietal lobesLower loops anteriorly and laterally around inferior horn of lateral ventricle (Meyer’s loop) via temporal lobe to visual cortex

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Visual Cortex

Termination of visual nerve fibres – synapseOccipital lobe – calcarine fissureFovea; tip of occipital pole (posterior)Temporal crescent; most anteriorSuperior (above), inferior (below)

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Humphrey Analysis

Threshold or

suprathreshold

analysis

Off-centred equal spacing of central stimuli

Disease specific peripheral presentations

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Octopus Analysis

Physiology related test pattern

Higher density of stimuli in central field

Follow nerve fibre bundle layer patterns

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Analysis

ValuesComparisonProbabilitiesDefect (Bebie) curveDiffuse defectGlobal indicesCluster GraphPolar GraphGlobal Trend Cluster Trend PolarTrend

Absolute thresholds

Scales and defect depth

Percentile of normality

Ranking of defect values

Deviation from 50

th

%

Mean sensitivity and defect

Analysis of regional deviations from normal

All local defects mapped to a representation of the optic disc for structure/function comparison

Change rate, fluctuation and significance calculation

Regional change rate and significance calculation

Pointwise

linear regression analysis mapped to the optic disc

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Structure versus Function

Correlation between structural changes (imaging of retinal nerve fibre layer) and functional changes (visual field result)

Structural changes at the optic nerve head and/or retinal nerve fibre layer tend to precede visual field changes early in the disease

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Polar analysis

Topographic map correlating areas of the visual field (A) with areas of the optic disc (B).

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Function specific perimetry

Standard achromatic perimetry (white on white) detectable only when a substantial number of ganglion cells lost (≈ 30%)

Functional evaluation of retinal ganglion cells for early detection of glaucoma

Temporally modulated stimuli are more sensitive than W-W perimetry

Functional tests isolate subpopulations of retinal ganglion cells which lose function earlier than other ganglion cell types

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≈80% parvocellular ganglion cellsSensitive to colour and contrastHigh pass resolution perimetry≈ 15% magnocellular ganglion cellsSensitive to temporally modulated stimuliCritical fusion frequency Frequency doubling technology≈ 5% koniocellular ganglion cellsSensitive to blue-yellow componentsB-Y perimetry

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Function specific perimetry

HRP: High-pass resolution perimetryRing shaped targets of 14 different sizes used to determine resolution of central 30 degrees of visual field

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Function specific perimetry

CFF: Critical fusion frequency perimetry

Measurement of flickering stimulus at different locations ranging from slow to fast (0-50Hz) speed until the stimulus appears to be a continuous light rather than flickering

Not sensitive to lens changes, e.g. cataract

FDT: Frequency doubling technology

Detects the sensitivity for discriminating the frequency doubling stimulus

Stimulus is a large 10 x 10 square of black and white bars, flickering at 25 Hz

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Function specific perimetry

SWAP: Short-wavelength automated perimetry

Isolates blue sensitivity (S cones) from green (M) and red (L) cones by suppressing the relative sensitivity of M and L cones with a bright yellow background and using a blue stimulus

S- cones become more sensitive

Practical restrictions:

Cataract

Increased variability of threshold

Tiring and difficult test – reliability issues

Long test duration

Considerable learning curve

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Factors influencing visual fields; Artefacts

Anatomical features of the face

Ptosis

Miotic pupil

Uncorrected refractive error

Refractive corrections

Cataract

Attention of the patient

Technique of the examiner

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Aids to interpretation

Knowledge of visual pathway and:

Related visual field defects

Related

signs

Related symptoms

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Retina and optic disc

Reduced visual acuity

Afferent pupillary defect

Reduced colour vision

Reduced contrast sensitivity

Perceptual problems

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Optic nerve

Reduced visual acuity

Afferent pupillary defect

Reduced colour vision

Reduced contrast sensitivity

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Optic chiasm

Postfixational

blindness

Hemifield

slide

See saw nystagmus

Bowtie atrophy

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Optic tract

Afferent pupillary defect

Optic atrophy; asymmetrical

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Optic radiations

Temporal lobe lesion

central

achromatopsia

,

agnosia

, alexia, hallucinations, seizures, Bell’s reflex

normal depth and motion

Parietal lobe lesion

reduced stereopsis, spatial localisation and motion,

agnosia

, reduced OKN, poor fixation, left/right confusion, Bell’s reflex,

hemiparesis

normal colour and form, discrimination and recognition of faces

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Visual cortex

90% without other neurological signs

Reading difficulties

Cortical blindness

Riddoch

phenomenon

Anton’s syndrome

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Differential diagnosis

Horizontal meridian respected in retinal and optic nerve head lesions

Vertical meridian respected in

chiasmal

and post

chiasmal

lesions

Bilateral defects in post

chiasmal

lesions

Deterioration of vision, RAPD,

fundus

abnormalities seen in pre chiasm lesions

Case history

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Perimeter comparison

Surface luminance (apostilb:asb)Stimulus luminanceLuminance adjusted by combination of neutral-density filtersGraded in decibels (dB). Each dB equivalent to 0.1 log unit10dB equals 1 log unit or 10-fold change in intensity

Stimulus luminanceGoldmann and Octopus perimeters generate a maximum stimulus luminance (0 dB) of 1,000 asbHumphrey perimeter uses a 10,000-asb bulb (0 dB)Range of stimulus intensity greater for Humphrey

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Perimeter comparison

Surface background luminanceGoldmann and Humphrey instruments use 31.5 asb, while past Octopus models use 4 asbOctopus 900 use 31.4 asb

Stimulus duration100ms for Octopus 200ms for Humphrey

Programme strategies

Humphrey perimetry: SITA analysis and threshold standard or fast bracketing strategies

Octopus perimetry:

Peritrend

analysis and threshold dynamic or TOP strategies

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Choice of Perimeter

Goldmann

Octopus

Humphrey

Manual

Kinetic

Peripheral

Blind spot

Poor VA / fixation

Advanced defects

Driving

Manual

Automated

Kinetic

Static

Peripheral

Central

Sensitive to early loss

Repeatability

Blind spot

Poor VA / fixation

Advanced defects

Driving

Automated

Static

Central

Sensitive

to early loss

Repeatability

Driving

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Common choices

First visit

Screen 24-2 SITA fast, G TOP

Screen: glaucoma 24-2SITA standard, G dynamic

Pathology 24-2 SITA standard, G dynamic

Follow-up 24-2/30-2 standard, G dynamic

Constricted field 10-2, LV

Hydroxychlorequine

Macula, M dynamic

Peripheral pathology 60-4, Kinetic

DVLA

Estermann

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Over to you!

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Summary

Visual pathway anatomy

Visual field results for kinetic and static

perimetry

Artefacts of visual fields

Aids to interpretation and localisation of lesion

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rowef@liv.ac.uk