visual field analysis--interpretation
TRANSCRIPT
Humphrey visual field printout ----interpretation
Prof. Md. Shamsul HaqueSBMCH, BARISAL, BANGLADESH
Retinal nerve fibre arrangement
Nerve fibres arrangement at optic disc
What is visual field ?
Aims of today,s topic
Will be able
• to identify field defect• to recognize that field defect is due to glaucoma or neurological lesion•to know that field defect is progressive or not
What is perimetry ?
Bjerrum,s screen Lister octopus
Humphrey
Goldmann
Types of perimetry
a. Kinetic…stimulus moves confrontation, lister, tangen screen,
Goldmann b. Static …stimulus does not moves HVFA, OCTOPUS
1970………OCTOPUS, Unpopular
1984………HUMPHREY, Popular
Advantages of Goldmann perimetry Low vision patientNeurological patientPeripheral field to be evaluatedMalinger patients
Difference between kinetic and static perimetryStatic Kinetic 1.VFD detect earlier with 1. Detect when 40% damage 20% defect2. Area fixed but stimulus 2. Intensity is fixed but varies in intensity stimulus moves from non-seeing to seeing area3. Three dimensional 3. Two dimensional 4. Computerized 4. Not computerized 5. Threshold type 5. Non threshold type6. Less error 6. More error7. Both glaucoma and 7. Good for neurological neurological
Some importants terms
• Apostilbs(asb)
• Decibel(dB)
• Threshold
• Supra-threshold
• Infra-threshold
Apostilbs(asb) and Decibels(dB) relationship
•Threshold
•Suprathreshold
•Infrathreshold
Aposilbs, Decibels , Retinal sensitivity relation
Humphrey visual field test, Classification
Two types– on the basis of strategies
1. Threshold test—using threshold stimulus for diagnosis of glaucoma and neurological lesions
2. Screening test– using suprathreshold stimulus for detection of glaucoma
1.Threshold test—is of three types
a.Central tests b.Peripheral tests c.Special tests
central 30-2 peripheral 60-4 neurological -20
central 24-2 nasal step neurological –30
central 10- 2
macular program
Central 30- 2 threshold test pattern•No of test points –76•Point density is 6° (distance between the two points)•Bare area(non-testing area) is 3° from the fixation point •Extension of testing area from the fixation point is 30°NB: one eye is tested at a time, other eye is occludedFixation should be steady and monitor throughout the test
Central 24-2 threshold test pattern
•No. of test points---54•Point density is 6° (distance between two points is 6°)•Bare area (non-seeing area) is 3° from the fixation point•Extension of testing area from fixation point is 24°
Central 10-2 threshold pattern
•No. of points----68•Point density is 2°(distance between two points is 2°)•Bare area(non-seeing area) is 1° from the fixation point •Extension of testing area from the fixation point is 10°
Macular program
•No. of teat point is 16•Point density is 2°(distance between two points is 2°)•Bare area (non-seeing area) is 1° from the fixation point •Extension of testing area from the fixation point is 5°
Why we select 30-2/24-2/10-2 central threshold test pattern instead of 30-1/24-1/10-1
-*
Central 30-2
•No. of test points is 76•Testing points are away from vertical and horizontal axes•Bare area is 3° from the fixation point
Central 30-1
•No. of test points is 71•Testing points fall upon the vertical and horizontal axes•Bare area is 6° from the fixation point
Threshold testing strategies Threshold testing strategies is of two types 1.Old standard strategies – full threshold strategies/standard threshold strategies2. Newer threshold trategies a. FAST PAC b. SITA standard c. SITA fastSITA– Swedish Interactive Threshold Algorithm
Humphrey visual field test printout(single field)----interpretation We can divide the printout into 8 zonesZone—1, Patients data and test dataZone—2, Foveal threshold and reliable indicesZone—3, Gray scaleZone—4. Patients raw dataZone—5, Total deviation plotZone– 6, Pattern deviation plotZone—7, Global indicesZone—8, Glaucoma hemifield testZone—9, Eye tracking(±)
Identify 8 zones of the Humphrey printout
Zone—1, Patients data and test data
Zone—2 ,Foveal threshold and reliable indices
Zone—3, Gray scale
•RP•PRP•Peripheral retinal degeneration•Retinoschiasis •Aphakic glass
Zone—4, Patients raw data
Zone –5, total deviation plot,has two components A. Total deviation numerical plot(TDNP)B. Total deviation probability plot(TDPP)
A
B
Zone –6, pattern deviation plot,has two components A.Pattern deviation numerical plot(PDNP)B. Pattern deviation probability plot(PDPP)
A
B
•Mild to moderate generalized depression are eliminated •Deep focal deviations are height lighted •Machine adjusts these values and the new resultant values are displayed as symbolic form in PDPPFactors influencing the pattern deviation plot are•Hazy media•Miotic pupil
Zone—7, Global indicesMD—mean deviation • Indicate average severity of the field loss• Expressed in decibel(Db) value•Machine analyses and calculates how often these values are seen in general population, if the value is positive it indicates pt,s score is better than normal person of the same age
PSD—Pattern Standard Deviation •This is a measure of focal loss or variability within the field •If score is high, damage is more
Zone—8, Glaucoma hemifield test(GHT)
GHT
GHT→ Glaucoma Hemifield TestCompare mirror image locations of superior and inferior retina and gives five comments 1. GHT—outside normal limit ,if difference
found in 1% population2. GHT—borderline , if difference found in up
to 3% population3. GHT—abnormally low sensitive, best
sensitive part is seen in less than 5% of the population
4. GHT—abnormally high sensitive, best sensitive part is seen is more that found in 99.5% population
5. GHT—within normal limit, when none of the above 4 conditions are seen
Zone –9, Eye tracking
SWAP→ Short Wave length Automated Perimetry
When and why SWAP strategies is done
•Done to detect very early glaucomatous damage
•Background colour of the machine bowl is yellow –which desensitize the red and green cones
•Colour of the stimulus is blue which activates the blue cones only
Frequency doubling technology(FDT)
•This is a latest machine•It utilizes latest technology •Machine is upto 97% sensitive to detect glaucomatous defect
Visual field defects•Generalized depression→ both central and peripheral fields are depressed as in cataract•Peripheral depression → only peripheral field is depressed as in RP•Temporal contraction → only temporal field is depressed as in aging people(Depression means reduced sensitivity of the retina)
Scotomas → non-seeing area of the visual field Types:•Absolute •Relative •Positive •Negative
Cont.•Hemifield defect•Altitudinal field defect•Central scotom •Paracentral scotoma•Centro-cecal scotoma •Arcuate scotoma•Nasal step•Ring scotoma•Macular splitting•Bjerrum scotoma/siedel,s sign/siedel scotoma•Baring of the blind spot
Take home message
Octopus printout
Dense superior scotoma originate From BS, joins superior arcuate scotoma and finally joins the superior nasal step
By examining the gray scale and pattern probability plots of Right eye and Left eye , it is evident that this is a case of POAG .Right eye has tubular vision and Left eye has a bit more central vision than the right eye
Bitemporal hemianopia : Lesion is situated at the chaisma which damage the crossing nasal fibres of both optic nerves
Lesion : acute ischaemia in the frontal and parietal lobes affecting the superior fibres of the left optic radiation causing right inferior homonymous quardrantanopia , lesion is confirmed by MRI/MRA
Pie in the floor
Pie in the sky
Lesion: in the frontal and parietal lobes affecting the lower fibres of the right optic radiation causing left homonymous superior quadrantanopia –should be confirmed by MRI/MRA
Field of left eye
Superior altitudinal field defect (L/E)
Causes•AION• Optic neuritis • Hemiretinal vein occlusion•Hemiretinal artery occlusion •Optic nerve coloboma •Glaucoma
Left homonymous hemianopiaLesion: in the right temporo-parietal region affecting the right optic radiation MRI shows haematoma of the right temporo-parietal region
Thank you
Smile always