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Performing Exams Probe Usage in Scanning
Longitudinal Probe Positions
Longitudinal scans are radial scans encompassing only
one clock per slice, from the posterior pole to the anterior
periphery. Therefore the optic nerve shadow (the center
of the "clock") will be at the bottom of every longitudinal
scan so long as it is aligned properly.
All longitudinal scans should be labeled with an "L" and
th
e clock hour of the meridian being examined; i.e. L10,
L3 etc.
Transverse Probe Positions
Transverse probe positions demonstrate the lateral
extent of pathology, encompassing approximately six
clock hours in one slice. The patient’s gaze is directed
toward the area of interest and the probe is placed on
the opposite sclera with the marker oriented parallel to
the limbus.
In horizontal transverse approaches the marker is aimed
nasally so the upper portion of the screen represents the
nasal section of the globe (the upper portion of the
screen will always be 3:00 in the right eye, or 9:00 in the
left eye.
In vertical approaches the marker is aimed superiorly, so
that the upper portion of the screen represents the
superior portion of the globe (12:00 in OD or OS)
In oblique transverse approaches the marker is aimed
to
ward the upper portion of the globe so that the upper
portion is represented at the top of the screen.
Labeling of transverse scans is done according to the
portion
of the globe being examined (where the sound
beam is being directed) not by the position in which the
probe is being held on the globe.
First label the portion of the globe being scanned in the
center of
the display by recording the clock hour that
represents the meridian that lies in the center of the
screen followed by the locator that indicates how far out
in the periphery you are at the clock hour i.e 3P, 3EP etc.
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