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Numbers refer to the
diagrams.
1
Headband and chinrest: The
patient is positioned at the camera with his forehead against the band
and his chin in the chinrest.
2
Chinrest adjusting knob: The
vertical distance between the forehead band and the chinrest is adjusted
with this knob.
Positioning of the
patient’s head is critical to efficient retinal photography. Even
small movements of the head affect proper alignment.
3
External fixation target: The
patient views this small swivel light with the fellow eye (the eye not
being photographed). The light is positioned such that the view of the
eye being photographed is optimized as it changes position with the
fellow eye which is tracking the fixation target.
4
The lens barrel, or the objective lens:
Light from the camera is projected into the eye through this lens, and
light reflected from the eye is gathered by this lens on its way to the
film plane.
5
Diopter compensation knob:
The normal setting is used for retinal photography of the
"normal" eye. Other settings compensate for high myopes, high
hyperopes, and for anterior photography.
6
Angle or magnification lever:
A 50 degree, 35 degree, or 20 degree angle of view can be selected.
The
50 degree view gives a "wide angle" view, meaning more area of
the retina is visible. However, with the 50 degree view structures such
as the macula and optic nerve appear smaller in the frame (less
magnified). The 20 degree view is much narrower, but retinal structures
are larger in the frame (more magnified). Also, be aware that alignment
and focusing are easier using the 50 degree view and become more
difficult as the view is narrowed to 35 and 20 degrees.
7
Accessory mount: A Polaroid
camera back or a digital camera can be mounted here. It is controlled
(selected) by the "upper" button (24) on the control panel.
8
Eyepiece (finder): The
eyepiece must be adjusted for each operator to insure pictures that are
in focus.
9,18
Focusing knob: Located on
each side of the camera for easy reach.
10
Camera back and mount: A 35mm
camera body can be mounted here for slide photos or for film based
fluorescein angiography. This port is controlled (selected) by the
"lower" button on the control panel (24).
11
Shutter release button: This
button fires the flash, takes the photo, and advances the system to the
next frame. There is usually a footpedal release that can be used
instead of the control lever release.
12
Control lever: This controls
fine forward/backward, side-to-side, and vertical alignment of the
camera. Gross alignment of the camera is accomplished by sliding the
base of the camera in the desired direction.
13
Vertical control knob: Most
cameras incorporate the vertical control with the joystick, but some
have a separate vertical control knob.
14
Lamphousing: A removable
cover gives access to bulb(s).
15
Filter knob: Various filters
can be dialed into the light-path using this knob. The most commonly
used is the green filter (red free) which is used with black-and-white
film to accentuate blood vessels.
16
Illumination diaphragm lever:
This lever is set to "N" if dilation is sufficient for good
illumination of the retina. If the pupil is small, this lever can be set
on "S" to provide better illumination. Small pupil
illumination is also improved by using the 35 or 20 degree angle
(magnification) settings (6).
17
Internal fixation target:
This device inserts a pointer into the camera light path such that the
photographer and the patient can see it. The patient is instructed to
look at the tip of the pointer as the photographer moves it to align the
patient’s eye. This device is particularly useful if the patient
cannot fix on the external fixation device (3) with the fellow eye. A
disadvantage is that the pointer appears in the photograph.
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