I need the definition of pattern standard deviation as it relates to
visual field tests in Ophthalmology.  It needs to be an official
definition like from a textbook on visual fields.  I also need the
reference if possible.

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Request for Question Clarification by tutuzdad-ga on 06 Mar 2004 15:04 PST

I found a great definition by a leading University's School of
Ophthalmology if that will suffice as an answer.

Regards;
tutuzdad-ga

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Clarification of Question by hilary77-ga on 07 Mar 2004 13:52 PST

Sorry it took so long to respond.  The comment from njbagel-ga is a
good description and a good reference, and I think that it will meet
my needs.  A definition from a University would also be fine as long
as is a website reference. It would also be nice if the definition
from the University is more consice.  But, both will work.
Sorry again for the delay.

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Request for Question Clarification by tutuzdad-ga on 08 Mar 2004 12:53 PST

The reference I found provides a general, but brief, definition of
'pattern standard deviation' in general rather than relying on
hypothetical scenarios of potential theraputic uses that the commenter
provided.

Would you like me to post it as an answer and close your question for you?

Regards;
tutuzdad-ga

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Clarification of Question by hilary77-ga on 08 Mar 2004 15:08 PST

Yes that would be great. Thanks.

Dear hilary77-ga:

Thank you for allowing me an opportunity to answer your interesting question.

This direct definition comes from the INDIANA UNIVERSITY SCHOOL OF
OPHTHALMOLOGY glossary of terms:

?Pattern Standard Deviation (PSD) - This is a measurement of the
degree which the shape of the patient's measured field or hill of
vision departs from the "NORMAL" age-corrected reference field model.
The value is expressed in decibels and any value of 2dB or greater
will have a (P) value next to it indicating the significance of the
deviation.?

AUTOMATED PERIMETRY
http://www.opt.indiana.edu/Riley/HomePage/Automated_Perimetry/Text_Auto_perm.html


Below you will find that I have carefully defined my search strategy
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INFORMATION SOURCES

INDIANA UNIVERSITY SCHOOL OF OPHTHALMOLOGY
http://www.opt.indiana.edu/

SEARCH STRATEGY


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Google ://www.google.com




SEARCH TERMS USED:

?Pattern Standard Deviation?

PSD

Corrected Pattern Standard Deviation

CPSD

Excerot from:
Standard perimetry.
Anderson DR - Ophthalmol Clin North Am - 01-JUN-2003; 16(2): 205-12, vi
From NIH/NLM MEDLINE 


Several global indices may also be calculated, and the important ones
are the mean deviation (MD) and pattern standard deviation (PSD). The
MD and PSD are mathematically the weighted mean and standard deviation
of all the total deviation values.

The MD thus represents the general net magnitude of the abnormality of
the visual field. (Mean defect, mean loss, and mean sensitivity are
other indices of overall loss on past and present instruments of
various manufacturers.)

The PSD represents the homogeneity of any abnormality. It is small if
all locations deviate from normal by the same amount, and a minimal
value represents the expected variation caused simply to variability
of testing. The PSD becomes larger when field loss is more marked in
some locations than in others. The clinician is helped to recognize
that the disease produces more visual change at some locations than at
other locations and can distinguish the patient's disease from
conditions that cause a homogenous diffuse loss of visual threshold in
all locations of the visual field. When testing is conducted in an
older patient who has glaucoma (characterized by some locations being
more affected than others) and also has cataract (which affects all
parts of the visual field more or less equally), the MD index reflects
the summed loss from both diseases, and the PSD reflects the disease
that produces localized loss. In the single-field evaluation, the PSD
global index helps the clinician to recognize the presence of glaucoma
in addition to the cataract. (The loss variance [LV] index, used in
particular by the Octopus perimeter, quantifies localized loss and is
simply variance, the square of the standard deviation on which the PSD
index is based. LV also differs from PSD because it is not based on
weighted values.)


-d