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47 Vis ua l field tes ts
E l e k t r o n E y e T e c h n o l o g y 2 0 1 8
3 .2 .5 .2 T otal Dev iation
Total Deviation values are the difference between the measured threshold and that expected
from an age-matched normal eye.
They are presented in two different forms:
Absolute values in decibels (dB).
Symbols representing the probability that the threshold measure comes from a normal
eye. The probability values take into account the variability in threshold estimates at
each test location.
Positive values indicate a higher than average sensitivity.
Th e a b o ve f i g u r e s h o w s t h e To t a l D e vi a t i o n (l e f t ) a n d Pa t t e r n D e vi a t i o n (r i g h t )
va l u e s a s s e e n i n t h e s t a n d a r d p r i n t o u t . Ab s o l u t e va l u e s a t t h e t o p a n d
p r o b a b i l i t y s ymb o l s b e l o w .
Example:
If the measured threshold was 25dB in a person of 40 years of age and the normal value for that
location was 30dB, then the Total Deviation value would be -5dB.
Total Deviation values appear on the standard printout .
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