interpreting visual fields
DESCRIPTION
Visual field testing is an important diagnostic consideration in the evaluation of patients with many different types of pathologies. Most commonly, it is used for conditions affecting the optic nerve and other forms of neurological disease; but it’s also helpful for retinal conditions and instances when visual field function needs to be measured. At the end of the lecture optometrists will have a better understanding of testing and interpreting visual field results.TRANSCRIPT
Interpreting Visual Fields
Andrew WhiteBMedSc(Hons), MBBS, PhD, FRANZCO
Glaucoma consultant, Westmead HospitalClinical Senior Lecturer, University of Sydney
Chair, Expert Advisory Panel, Glaucoma AustraliaBoard Member, World Glaucoma Association
Gosford Eye Surgery
Visual Field Testing Confrontation Bjerrum Goldman Humphrey Visual Field
Standard white on white SITA (Swedish Interactive
Threshold Algorithm) Standard Fast
SWAP (Short Wavelength Automated Perimetry)
Octopus Medmont
FDT: Frequency Doubling Technology
Relies on detection of a flickering grating
Attempt to make it perimetry but never originally designed for that – physiologically impossible1.
Cheap, desk mounted and sensitive
No reliable progression analysis
1: White et al. Invest Ophthalmol Vis Sci. 2002;43:3590–3599
Humphrey Visual Field• 24-2 White on White is the standard• Can be full threshold, SITA standard
or SITA Fast. – Biggest difference between them is
time• SWAP and 30-2 less useful• 10-2 For advanced Glaucoma• Not directly comparable with
Octopus or Medmont (different algorithms)!
• FDT not comparable at all.• If you start with a paradigm, you
should keep the same to make it meaningful.
Things to Look For On a Humphrey
A Normal Visual Field
If The Field Is Not Normal....
How long did it take? (a well trained alert person will take 3-5mins SITA Fast)
What was fixation loss? What was false +v and false -ve (gave up or
trigger happy?) Clover leafing? Were they asleep? (a flat eye tracker reading) Were they properly refracted? Do they have a ptosis/heavy brow?
Non Diagnostic FieldsClover Leaf Pattern Lens Artifact
Ptosis
Glaucomatous Fields
Progression
Visual Fields are Inherently Noisy
X X X
X
X
The one bad VFVisu
al F
ield
Inde
x
20
40
60
80
100
0
X X X
X
One Bad VF -probablyVisu
al F
ield
Inde
x
20
40
60
80
100
0
XXX
X X X
XX
Progression
X
X
Visu
al F
ield
Inde
x
20
40
60
80
100
0
Rates of Visual Decay• Glaucomatous
progression is almost 10 times faster than the normal rate of decay of visual function with age.
• Structural change usually preceeds functional loss but not always
• We are most concerned with progression in the order of 1.5-2dB per year
Common RoP (0.6 dB/year) in a clinical population with glaucoma
Mean RoP for normal visual decay (0.07 dB/year)
Mean RoP (1.1 dB/year) in untreated glaucoma
Heijl et al. Arch Ophthalmol 1987;105:1544–9.Haas et al. Am J Ophthalmol 1986;101:199–203.Heijl et al. Ophthalmology 2009;116:2271–6.
Guidelines for VF Testing• Ideally need 3 visual fields/yr
to determine progression1
• Medicare allows 2 per year• Young (<80) stable patients
and suspects monitored 6 monthly
• Older and very stable patients yearly
• High risk patients may need 3-4 fields/year
• Often combined with optic disc imaging
1: Chuhan et al. Br J Ophthalmol. 2008 92(4): 569–573
Neurological Causes of Field Loss Refractive Stroke Optic neuritis/
neuropathy Chiasmal tumours Raised intracranial
pressure
Is Something Else Causing The Field Loss?
Tilted discs Myopia Disc Drusen Retinal Disease
Take Home Messages• Not every visual field defect is
glaucoma!• Structural change often proceeds
functional change• Progression on visual fields over
time important. • Many need several tests to
differentiate from noise in the data
• Need to compare the same test each time to be meaningful
• 24-2 HVF the Gold Standard
Q1
• What is the gold standard visual field?
• 1. 24-2 White on White Humphrey• 2. FDT• 3. 30-2 White on White Humphrey• 4. Medmont Perimetry
Q2
• Does FDT have validated progression analysis?
• 1.yes• 2.no
Q3
• What is the rate of progression of visual field loss in treated glaucoma?
• 1: 1.5 dB yr• 2: 0.07dB yr• 3: 1.0 dB yr• 4. 0.6 dB yr
Q4
• What rate of glaucoma progression means an increase in treatment is warranted?
• 1: 0.5 dB yr• 2: 1.5-2 dB yr• 3: 1-1.5dB yr• 4: Any progression
• Q1-1• Q2-2• Q3-4• Q4-2