rarebit test principles - use stimuli of minimal subtense (ideally smaller than receptive fields), -...
Post on 16-Dec-2015
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Rarebit test principles- use stimuli of minimal subtense (ideally smaller than receptive fields),
- at high & fixed contrast,
- check once only for the presence of function (no thresholding),
- in ever-new, non-overlapping locations;
- calculate hit rate
- briefly exposed (to negate sweep gains);
Model of receptive field matrix with 10% ”holes”.
Model of receptive field matrix with 10% ”holes”. A macro stimulus can activate several good fields. Micro stimuli (”rare bits”) in ever new positions should on average activate 9 fields out of 10.
Key rarebit parameters:
Dot size: 0.5 x MAR** Minimum Angle of Resolution
Contrast: high & fixed
Main result parameter Hit Rate =
Sum of responses Sum of presentations
Expected normal hit rate 100% (except at blindspot and in angioscotoma)
Case of mild optic neuritis
HRP (High-pass Resolution Perimetry)
RBP (Rarebit Perimetry)
VA = 0.8 = 20/25
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