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

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0

X X X

X

One Bad VF -probablyVisu

al F

ield

Inde

x

20

40

60

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100

0

XXX

X X X

XX

Progression

X

X

Visu

al F

ield

Inde

x

20

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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