ESCRS Dr Fiona Rowe University of Liverpool Goals Visual pathway anatomy Methods of perimetry use for Humphrey visual field analyser Goldmann perimeter Octopus 900 perimeter Visual field printout options ID: 353820
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Slide1
Visual field evaluation
ESCRS
Dr Fiona Rowe
University of LiverpoolSlide2
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. Slide3
Visual pathway and topography
Retina
Optic disc
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate body
Optic radiations
Visual cortexSlide4
Retina
Papillomacular bundle – fovea
Nasal retina
Superior retina
Inferior retina
Temporal retina
Central fibres develop firstSlide5
Optic disc
Representation of retinal nerve fibresSlide6
Optic nerve
Fibres become myelinated
Representation of retinal nerve fibresSlide7
Optic chiasm
13mm wide
Surrounded by pituitary gland, third ventricle, thalamus, cavernous sinus
Crossing of nasal retinal fibres
Superior (above), inferior (below), macular (central)Slide8
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)Slide9
Lateral Geniculate Body
Diencephalon, midbrain
First synapse of retinal nerve fibres
Rotate through 90 degrees
Superior (medial), inferior (lateral)
6 layers
Macular fibres in all 6 layers
Ipsilateral temporal fibres; 2, 3, 5
Contralateral nasal fibres; 1, 4, 6Slide10
Optic radiations
90 degree realignment of nerve fibres
Superior (above), inferior (below)
3 groups
Upper and central pass directly to visual cortex via posterior temporal and parietal lobes
Lower loops anteriorly and laterally around inferior horn of lateral ventricle (Meyer’s loop) via temporal lobe to visual cortexSlide11
Visual Cortex
Termination of visual nerve fibres – synapse
Occipital lobe – calcarine fissure
Fovea; tip of occipital pole (posterior)
Temporal crescent; most anterior
Superior (above), inferior (below)Slide12
Humphrey Analysis
Threshold or
suprathreshold
analysis
Off-centred equal spacing of central stimuli
Disease specific peripheral presentationsSlide13
Octopus Analysis
Physiology related test pattern
Higher density of stimuli in central field
Follow nerve fibre bundle layer patternsSlide14
Analysis
Values
Comparison
Probabilities
Defect (
Bebie
) curve
Diffuse defect
Global indices
Cluster Graph
Polar Graph
Global 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 discSlide15
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 diseaseSlide16
Polar analysis
Topographic map correlating areas of the visual field (A) with areas of the optic disc (B).Slide17
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
Slide18
≈80% parvocellular ganglion cells
Sensitive to colour and contrast
High pass resolution perimetry
≈ 15% magnocellular ganglion cells
Sensitive to temporally modulated stimuli
Critical fusion frequency
Frequency doubling technology
≈ 5% koniocellular ganglion cells
Sensitive to blue-yellow components
B-Y perimetrySlide19
Function specific perimetry
HRP: High-pass resolution perimetry
Ring shaped targets of 14 different sizes used to determine resolution of central 30 degrees of visual fieldSlide20
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 HzSlide21
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 curveSlide22
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 examinerSlide23
Aids to interpretation
Knowledge of visual pathway and:
Related visual field defects
Related
signs
Related symptomsSlide24
Retina and optic disc
Reduced visual acuity
Afferent pupillary defect
Reduced colour vision
Reduced contrast sensitivity
Perceptual problemsSlide25
Optic nerve
Reduced visual acuity
Afferent pupillary defect
Reduced colour vision
Reduced contrast sensitivitySlide26
Optic chiasm
Postfixational
blindness
Hemifield
slide
See saw nystagmus
Bowtie atrophySlide27
Optic tract
Afferent pupillary defect
Optic atrophy; asymmetricalSlide28
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 facesSlide29
Visual cortex
90% without other neurological signs
Reading difficulties
Cortical blindness
Riddoch
phenomenon
Anton’s syndromeSlide30
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 historySlide31
Perimeter comparison
Surface luminance (
apostilb:asb
)
Stimulus luminance
Luminance adjusted by combination of neutral-density filters
Graded in decibels (dB). Each dB equivalent to 0.1 log unit
10dB equals 1 log unit or 10-fold change in intensity
Stimulus luminance
Goldmann and Octopus perimeters generate a maximum stimulus luminance (0 dB) of 1,000
asb
Humphrey perimeter uses a 10,000-asb bulb (0 dB)
Range of stimulus intensity greater for HumphreySlide32
Perimeter comparison
Surface background luminance
Goldmann and Humphrey instruments use 31.5
asb
, while past Octopus models use 4
asb
Octopus 900 use 31.4
asb
Stimulus duration
100ms 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 strategiesSlide33
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
DrivingSlide34
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
EstermannSlide35
Over to you!Slide36Slide37Slide38Slide39Slide40Slide41Slide42Slide43Slide44Slide45Slide46Slide47Slide48Slide49Slide50Slide51
Summary
Visual pathway anatomy
Visual field results for kinetic and static
perimetry
Artefacts of visual fields
Aids to interpretation and localisation of lesionSlide52
rowef@liv.ac.uk