O2B Visual Fields

• Assess peripheral vision
• Assess the integrity of the visual pathway
•  Diagnose ocular and neurological diseases
•  Monitor the progression of ocular diseases

• Glaucoma / suspicion of glaucoma
• Reduced visual acuity
• Unexplained headaches
• Neurological disorders  
• Benign optic disc conditions
• Retinal disorders – inflammations and dystrophies
• Medications
• Assessing fitness to drive
• Evaluating sport fitness especially elite levels

• Direct assessment of visual function
• More than just central vision
• Non-invasive
• Can typically detect cheating
• Repeatable examination techniques – good for monitoring progression
• Good for differential diagnoses of diseases – typically obtain characteristic VF losses
• Extra income for practitioner

• Machines not portable
• Expensive equipment
• Time consuming
• Subjective assessment by patient

• Superior margin = frontal
• Inferior margin = maxillary
• Medial margin = frontal lacrimal and maxillary
• Temporal margin = frontal and zygomatic

• eccentricity
• adaptation level
• nature of stimulus test

• steeper on the nasally
• steeper superiorly

• 2D section of the island of vision
• 0-5- steep slope at fovea
• 5-40- flatter central VF
• >40- steep edge of VF

Diffuse visual field loss / Depression – generally caused by pre-retinal opacities e.g. corneal oedema, cataract

• Focal visual field loss - An area of reduced sensitivity surrounded by an area of normal sensitivity – focal point of damage in retina or visual pathway
• Relative scotoma
• Absolute scotoma

Visual field contraction – caused by conditions which affect the peripheral retina

• confrontational
• amsler grid
• tangent screen

• Fast and flexible
• Good for measuring severe VF loss or measuring absolute loss
• Good for multiple handicapped
• Excellent in low vision and neurological cases

• It’s not standardized
• Not good for measuring the depth of scotoma
• Can’t pick up shallow scotomas well
• Not as good in quantifying central field
• Requires an experienced clinician

• Relatively gross method used to screen for the presence of unsuspected field defects- insensitive
• compares px VF to practioners

• target confrontation: dynamic movement of small target in VF until seen
• finger wriggling: dynamic movement of fingers in VF until seen
• finger counting:

stim presentation and manipulation is controlled by practioner

• a stimulus of constant size and shape is moved across VF
• moved frmo periphery until seen

stim apears in stationary loactions but may change in characteristics

estimate threshod of eye at different locations

present stim above threshold/ recrod if seen

• more sensitive than confrontational
• Non-reflective black screen
• Small central white fixation target
• Concentric circles stitched at
• 5 intervals
• A selection of targets

• px sits 1m away-tests 25-30deg
• target is moved from periphery until seen- scotomas

• black lines on white bg
• viewed at 28cm, one box= one degree
• wavy lines/missing lines

10 degree either side of fixation

• macular damage: AMD, diabetic maculopathy, central serous retinopathy
• sees wavy lines or lines missing

• Stimuli projected onto the surface of a bowl
• Stimulus can becontrolled by the practitioner
• A stylus which moves in conjunction with the control of the stimulus can mark field extend on pre-printed chart paper

• Presents 2,3 or 4 stimuli in VF
• Patients report how many lights they saw
• Light intensity can be altered using filters
• Results are marked on a pre-printed sheet

• tests sensitivity for specific points in the peripheral visual field
• suprathreshold+threshold
• px presses on the button when they see the stimulus
• different colours, size and intensities are displayed

similar to HVFA but on PC

• P-80, M+K:10
• less redundancy, more noticealbe in MK cells

• based on K cell pathway
• decreased sensitivity to blue wavelength
• more sensitive to glaucomatous changes
• yellow-background- is used to de-sensitise the red and green cones
• affected by older ppl- yellowing of lens

• based on M cell pathway
• CFF- constant contrast
• TMP- contrast is varied

• Sinusoidal grating of low spatial frequency undergoes rapid counterphase flicker at high temporal frequency 
•  Stimulus appears to have twice the spatial frequency

• removes low spatial frequencies
• Patient must detect the presence of a ring – the core of the ring is brighter and the inner and outside edges darker

• obj
• records the electrical activity from 50-100 areas of the retina – electrodes either near the cornea or striate cortex

• Angular subtense
• physical size 
• goldmann size

• a variation in stimulus size
• relative size of the retina is the same for all testing distances

relative size of retina will vary according to testing distance

size replicates that unsed in the goldmann bowl perimeter

greater the sensitivity of the eye, the lower the intensity of light for the threshold and the lower the stimulus intensity

• cd/m3
• In perimetry- how bright the background and stimulus appear

intensities are measured in log scale - decibels

• luminance x duration = constant
• at a critical duration time, the brightness of the stimulus is proportional to the luminance and duration of the stimulus= temporal summation

• 100-250ms
• >100ms: reduces temporal summation
• <250ms: reaction time for the saccade of the eye to move to the periphery

• patient
• increase in px experience= steeper cruve and increased reliability
• decreased sensitvity in the eye: increased variability

tests whether the points are seen 6dB brighter than threshold of HOV

• 2 zone: all points either seen or not
• 3 zone: points that are missed are retested at max
• quantify defects: points missed retested for threshold value

• measured at 4 locations, each quadrant 9 deg away from fovea
• 2 reversal staircase: 4dB reduced to 2dB when results become positive
• threshold= dimmest light seen

• one reversal: single step 3 dB
• reduces testing time by 2/3rd
• less accurate

• Relies on prior knowledge
• number of false positives 
• will adjust presentation rate according to px response rate

4-2dB

3db single reservsal

• point grid falls on H + V axis
• shit cos leaves 6 deg gap of test points at fixation

• 3 degree gap at macula- smaller
• test on either side of midline

• 10-2: 68 pt grid spaced 2 deg apart- macula+ advanced glaucoma
• 24-2: 54 pt grid spaced 6 deg 30 deg nasally- glaucoma ONH
• 30-2: 76 pt grid 6 deg spacing- glaucoma, retina, ONH
• 60-4: 68 pt grid 30-60 deg- retinal changes, glaucoma
• Macula: 16 pt grid, 2 deg spacing, 5deg fovea
• Nasal step: 60 deg from fovea- glaucoma

full field to 60 deg

central vision testing- 10, 24 or 32 deg

• early: 24-2
• advanced: 10-2 more central due to loss of peripheral

• pupils: small, depressed
• Age: older= dec retinal, cisual pathway, senile miosis
• learning effect: increased performance= increased exp
• increased sensitivity= dec variability
• media opacities: dec retinal contrast
• fatigue: difficulties in attention
• anatomy: lids, spinal problem, prominent brow

• greater than 30%
• trigger happy

• greater than 30% 
• inattention/adfanvced field loss

compares measured sensitivity to age matched norms/HOV?

sensitiviy at each point below norms/HOV?

• loss in sensitivity
• generall loss or smeall area of depression

• small: diffuse loss
• large: focal loss

normal

generalised loss of sensitivity

Small localised defect

large defects + localised component

averages resting of same point: varibility testing

• index sensitive to focal loss
• separates real deviation from theose due to variability

decides if field loss is compatible with glaucoma diagnosis

a point/cluster of points decreased in sensitivity that is repeatable

glaucoma hemifield test norm- VF loss is compatible with glaucoma, PSD<5%

• single point p<0.5%
• 2 clustered points: p<5%, one point p<1%
• 3 or more points: p<5% + pattern of loss consistent with ocular pathlology

damage to large bundle of fibres: field loss reflects pathway

• eg glaucoma
• damate to specific bundles of fibres

• toxic amblyopia
• bilaterally due to tobacco/alcohol nutritional amblyopia
• damage to papillomacular bundle

• irregular field loss of rod/cone dystrophy: binocluar
• e.g. retinitis pigmentosa: damage to REP/PR- contricted fields

monocular- doent respect midline, rpe damage

• e.g. arm
• damage at rpe, relative/absolute defect

• e.g. retinal detachment
• damage doens't follow bundles of fibre and midline

• congenital defect, nasal bilateral
• relative temporal defect: doesnt respect vertical midline
• papilloedema: non- inflammatory swelling, ONHby increased intra cranial pressure- bilaterally enlarged blind spot

• formed by accumulation of deposits- calcified mitochondria
• congenital defect: bilateral
• arcuate defec: drusen pressures nerve fibre bundles
• arcuate scotoma: specific bundles damaged

• presses onto the optic chiasm
• nasal fibres affected first, then all

affects left of chiasm- LE temporal retinal fibres - affects nasal field

• superior fibres: medial
• inferior fibres: temporal
• macular fibres: centre
• incongruent: anterior
• congruent: posterior

visual field defect increases in congruency, more posteriorly

• field defects:
• pie in the sky
• pie on the floor
• increased in congruency, more posterior the fibres

• vascular: congruent, more posterior
• tumour: slow progression
• trauma: physical damage can affect one or both hemispheres