An Up-date on the GDx-VCC
Reference:
Reus , NJ and Lemij, HG, “Diagnostic Accuracy of the GDx-VCC
for Glaucoma”, Ophthalmology, October, 2004.
Select Quotes:
“We found that GDx-VCC parameters discriminate well between
healthy and glaucomatous eyes. The Nerve Fiber Index (NFI)
seemed to be the best parameter in classifying glaucoma.”
However, “x judgment of the printout as a whole resulted
in a better separation between normal and glaucomatous eyes
than judgment of single parameters. We therefore expect
that an assessment of the entire printout will further improve
the high accuracy of the GDx VCC.”
“x, an NFI value > 44 occurs over 60 times more often in
glaucoma patients than in healthy subjects. These data suggest
that glaucoma subjects rarely have an NFI of < 35 and healthy
subjects will almost never have an NFI of > 44.”
M & T Commentary
While the NFI value appears to be the single most predictive
parameter on the printout, the astute clinician will study
the entire printout to glean every morsel of information
to maximally enhance diagnostic value.
Obviously, the higher the NFI the more predictive of glaucoma,
and the lower the NFI the better, however this study provides
a more exacting quantification. Basically, if the NFI is 44
or greater, it is indicative of glaucoma, and conversely, if
the NFI is 35 or less, it is indicative of normal. Values
between 35 and 44 yield a neutral effect, and the GDx-VCC data
is non conclusive, meaning the doctor will have to lean more
heavily on the balance of the comprehensive diagnostic glaucoma
evaluation for clinical decision making.
The authors conclude: “xthe GDx-VCC features ease of administration,
short testing, and processing time, and ease of interpretation
of results.” We agree. |
