Published on March 20, 2014
Interpreting Visual Fields Andrew White BMedSc(Hons), MBBS, PhD, FRANZCO Glaucoma consultant, Westmead Hospital Clinical Senior Lecturer, University of Sydney Chair, Expert Advisory Panel, Glaucoma Australia Board 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 Fields Clover Leaf Pattern Lens Artifact Ptosis
Visual Fields are Inherently Noisy X X X X X The one bad VF VisualFieldIndex 20 40 60 80 100 0 X X X X One Bad VF -probably VisualFieldIndex 20 40 60 80 100 0 XX X X X X X X Progression X X VisualFieldIndex 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
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