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Henson Perimeter User Manual
© 2017 Elektron Technology
3 .2 .4 .4 P a t t e rn d e fe ct
Pattern defect values remove the effect of overall shifts in sensitivity to better
expose the pattern of any field loss.
At the end of each test the Henson softw are first calculates, for each test
location, the
values (the differences betw een the test result and that
of an age-matched normal). To then derive the Pattern defect values it offsets
the defect values according to the overall height of the patient's hill of vision. If
the patient has a less sensitive eye than that of an age-matched normal
(maybe they have some media opacities) then the Pattern Defect values w ill be
low er than the Total Defect values.
The offset is calculated from an analysis of the most sensitive regions of the
visual field and has a maximum amplitude of 6dB in either direction.
When there is a particularly large amount of visual field loss, the Pattern Defect
calculations become inaccurate and are not displayed.
The Pattern Defect values are presented in tw o 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.
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Содержание HENSON 8000
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