visual fields

Question 1

what are the type of visual defects

Answer 1

total ipsilateral visual loss

bilateral hemaniopia

left nasal hemianopia

right homonymous hemianopia

left homonymous hemianopia with macular sparing

Question 2

the more posterior the lesion.

Answer 2

the more congruous the defect

Question 3

where is the blind spot and why is it important

Answer 3

Blind spot is an important part of visual field assessment.
Can show disease activity.
Can also be used a reliability indicator

Question 4

what is the binocular visual field

Answer 4

The binocular visual field is the area where both eyes can see the stimulus
It extends approx 60 degrees on either side of the vertical midline
60 degrees superior and 75 degrees inferior
The inferior extent of field is affected by the nose

Question 5

what is the monocular field of vision

Answer 5

Monocular VF extent
160° horizontally
135° vertically

Question 6

what is the island of vision

Answer 6

Island of vision in a sea of darkness
Peak = Fovea
Bottomless pit = Blind spot

The sensitivity of the eye is not the same across the whole visual field.
The height of the island represent the sensitivity of the eye and we can see the sensitivity decrease with eccentricity
The peak = fovea with max sensitivity
The VF is described as an island of vision in a sea of darkness

Question 7

how to examine the visual field

Answer 7

There are 2 types of examination strategies: Kinetic and Static
Kinetic is manual and performed with the Goldmann Perimeter. Automated with Octopus
A stimulus of given size and intensity is moved from outside the visual field towards the center until the patient 1st notice the stimulus
The major advantage of kinetic perimetry is that the examiner has almost complete control over the examination and hence allows for flexibility
Static perimetry is automated and is often performed with the Humphrey Field Analazer
The stimulus is static and is presented pseudo-randomly in the visual field
The major advantage of static perimetry is it is automated, usually faster to perform and does not depend on inter-examiner variability

Question 8

what are the advantages of kinetic and static methods

Answer 8

Kinetic
e.g. Octopus
More laborious
Requires skilled examiner
Greater flexibility for testing areas of interest
Peripheral VF beyond the central 30 degrees

Static
e.g. Humphrey (HFA)
Faster testing procedures
No inter-examiner variability
Standardised
Central 30 degrees

Question 9

what part of the visual field to you assess

Answer 9

Measure central, peripheral vision or both?
Central VF assessment
60% of all retinal fibres
Shows most defects caused by ophthalmic disease
Peripheral VF assessment
Perform if pathology is likely to affect peripheral (outside central 30 degrees)

Question 10

what Is kinetic permietry

Answer 10

The Goldmann perimeter was introduced by Goldmann in 1945
It is a manual instrument, where the patient view inside the bowl and fixate a light in the center, while the examiner sits behind and look through the telescope, to see if Pt maintain good fixation.
The stimuli vary in size which is equivalent to intensity changes of 5dB steps. With each stimulus size an isopter is made

Question 11

what are the shortcomings of the manual Goldman perimmetry

Answer 11

No longer manufactured
Operator dependent
Lack of standardisation
Intra- & inter-examiner variability
Test-retest variability
Unavailable - alternative Projection perimeter (Takagi)

Question 12

what is the Isopter map

Answer 12

The isopter map is derived from the technique in which a stimulus of fixed size is moved from outside the island of vision (periphery) which can not be seen until seen
A series of points of equal sensitivity form an isopter

Question 13

what can be varied on goldmann

Answer 13

stimulus size , intensity and speed

Question 14

what is semi automated kinetic perimetry

Answer 14

Stimulus size & intensity
Stimulus speed
0°/s (static) or 2°/s - 10°/s (kinetic)
Operator choose start & end points of kinetic stimuli (vectors)
Automatic calculation of isopter and scotoma areas
Reaction time correction
Automatic retest of once established kinetic field
Comparable to manual Goldmann (Rowe and Rowlands, 2014)
Age and reaction time corrected values available (Grobbel et al 2016)

Question 15

why is the semi automated kinetic perimetry good

Answer 15

Promising test-retest variability
Preferred by patients over static perimetry
Lacking FP,FN and FL reliability indicators

Question 16

how to examinne field of investigation

Answer 16

Fields of Confrontation
Advantages
Quick, easy
Perform in clinic, wards
Can register as visually impaired on confrontation alone
Valuable in those unable to perform Goldmann / HFA
Children
Disabled
Stroke suffers
Disadvantages
Crude, screening test

Question 17

how to perform field of confrontation

Answer 17

This a crude technique to screen for any VF defects.
Method: Pt sit facing you approx 1m away. No glasses. The Pt is instructed to look at your nose and cover 1 eye (LE)
You cover your RE, so your VF’s will correspond with theirs
You can introduce target /fingers from the periphery, and Pt is asked to report when seen
You can hold up fingers in each of the 4 quadrants and ask how many fingers seen
Ask to identify face components
Quadrant finger counting
Colour comparison: hold 2 targets 15 degrees from fixation and ask about brightness of 2 red pens
Kinetic boundary testing: white 10-20mm target brought in from periphery

Question 18

what is the hfa

Answer 18

humphrey filed analyser

Threshold strategies
Estimates the threshold of seeing a stimulus at different test locations
c30-2 / c24-2 / c10-2
Threshold algorithms
SITA
Standard / Fast

Question 19

what is Sita

Answer 19

The full-threshold algorithm was 1st described by Bebie and Spar (1976)
They concluded the optimum psychophysical strategy was a ‘two reversal staircase’
The step size reduce from 4dB to 2dB after 1st reversal
E.g. if 1st presentation not seen, present stimulus intensity 4dB above, if then seen present 2dB below to ensure sees
Improved FP monitoring. FP is defined as when the patient press the button and no stimulus is presented (trigger happy). SITA use a time window when no patient response is anticipated. The minimum response time is defined as 180msec between presentation of stimulus and patient response and is adjusted according to the individuals response time.

Question 20

how to interpret grey visual field

Answer 20

When we try to interpret the visual field it is important to look at both the pattern dev plot as well as the grey-scale plot
The grey-scale plot gives us an overview of where the visual field defect is, next to we see the sensitivity values at each test location
The pattern dev plot compare each test location with an age-matched normal database and adjust for the general height of the hill of vision (i.e. diffuse loss) to show localised defects that may be masked by general depression which can be caused by e.g cataract.
So when you monitor a patient it is important to examine any change in the pattern dev plot
The GHT divides the upper and lower field into 5 sectors, and compare upper and lower field to identify any defects
MD is the weighted average of the total deviation values, insensitive to localised loss
The reliability indices can help us to determine how reliable the visual field is.
Fixation loss is determined by counting the number of times the patient press the button when a stimuli is presented as catch trials in the expected physiological blind spot location Fix Loss
False positive means the patient is trigger happy and press the button when there is no stimulus presented
False negative is defined as the number of times the patient fails to respond to a brighter stimulus than has already been seen
When interpreting a VF you should always examine the reliability indices. A visual field is defined as unreliable if the
FL > 20%, FP is >10-15% and/or FN >33%.
High FL may not only be due to the patient is unreliable but can also be caused by misalignment of the blind spot.
High FP error is the best indicator that the patient is unreliable (Newkirk et al. 2006)….
Research has shown that the FN rate increase with increasing depth of the defect

Question 21

how reliable is the visual field test

Answer 21

Heijl and Bengtsson (1996)
3 types of patients
Little/no learning effect
Greater learning effect between 1st & 2nd visit
Gradual learning curve lasting up to 5 visits
Recommendation for glaucoma
Minimum 2-3 VF ⇨ accept as reliable

Aydin et al (2015) showed a learning effect in normal adults from Turkey
More apparent in those aged >50 years and education below high school

Question 22

what pts may required a visual field test

Answer 22

Retinal & Optic Nerve Disease
Glaucoma
Optic Neuritis
Anterior Ischemic Optic Neuropathy (AION)
Neurological
Brain tumour e.g. chiasmal compression
Idiopathic Intracranial Hypertension (IIH)
Stroke
Children
In neuro-ophthalmology the aims of perimetry are:

Diagnostic

Monitoring

Functional assessment

Question 23

glaucoma testing - important - why?

Answer 23

Central threshold testing is recommended for assessing glaucoma (NICE 2017)

Taketani et al (2015) found that approximately 10 visual fields are required to accurately predict progression using HFA 24-2 SITA standard

Aptel et al (2015) progression of visual fields in POAG varies greatly among individuals

Question 24

describe glaucomatous progression

Answer 24

Early changes
Small paracentral defect
Often supero-nasally
? small degree of diffuse loss

…developing into
Nasal step
Larger arcuate scotoma

Advanced / end-stage loss
‘tunnel vision’
Residual islands in far periphery

Question 25

describe retinal and optic nerve disease

Answer 25

Optic Neuritis
Inflammatory disorder of optic nerve
Multiple sclerosis
Sudden onset of loss of vision
VF defect represent the effect on the papillomacular bundle
VF defect
Central scotoma
Arcuate defect
Nasal step
Inferior or Superior defect
Complete loss

Question 26

what neurological conditions may require a visual field test

Answer 26

Idiopathic Intracranial Hypertension (IIH)
Tumour
Orbital
Choroidal melanoma
Optic nerve
Chiasmal compression
Brain
Pituitary adenoma
Medullablastoma
Hypothalmic glioma/astrocytoma
Occipital tumour
Stroke / Vascular
Aneurysm
Thrombosis
Haemorrhage

Question 27

what are the symptoms of idiopathic intracranial hypertension

Answer 27

IIH
Symptoms
Headaches
Papilloedema
Swellling of optic nerve head secondary to ↑ICP
VF defects
Enlarged blind spot (EBS)
Constricted VF
Nasal loss/arcuate defect
Can correlate with clinical findings and OCT

Question 28

why is. monitoring of visual fields in idiopathic intracranial hypertension important

Answer 28

Monitoring of VF crucial as visual loss can be subtle, gradual and asymptomatic for a period of time

Question 29

what are the symptoms of chiasmal lesions

Answer 29

Chiasmal lesion
Symptoms
Headaches, hormonal changes, sexual dysfunction, fatigue, depression
VF defect
Bitemporal hemianopia
Binasal hemianopia is a very rare clinical phenomenon. It is due to bilateral lesions affecting the uncrossed optic fibres within the optic nerve

Question 30

what visual field defects are associated with stroke

Answer 30

Interruption of the blood supply to a localised area of the brain
Common VF defects
Homonymous hemianopia
Homonymous quadrantanopia
Consider patient’s ability & choose appropriate perimetry test

Question 31

what is a functional visual field defect

Answer 31

May hear this as malingering – not correct!
Spiralling field
Goldmann or Semi-automated kinetic perimetry
The patient produces a smaller and smaller field as the examination progress.
HFA does not give reliable answers, may be difficult to differentiate from organic VF loss

Question 32

what may be misdiagnosed as fvl

Answer 32

Most common in teenagers
Typically bilateral and involves both VA and VF.
1/5 had migraine, facial pain, or coexistent organic pathology.
Concomitant psychosocial events were mainly social in children and related to trauma in adults.
Normalization of visual function occurred in a majority of patients.
Early-onset macular dystrophies and hereditary optic neuropathies may be misdiagnosed as FVL.

Question 33

evlaute examining visual fields in children

Answer 33

manual

Advantages ☺
Better co-op
Allow breaks
Re-check areas

Disadvantages ☹
Qualitative
Lack of standardisation
? reliable for monitoring

Automated (HFA)
Advantages ☺
Quantitative
Standardised testing
Repeatable

Disadvantages ☹
Not designed for children
Boring
Requires good co-op