The Barron Radial Vacuum
trephine is comprised of
the trephine assembly, which
is connected with small silicone
tubing to a vacuum syringe
via a color-coded Luer-Lok
hub. Codes can be found
at the bottom of the
page. The hub should
not be disconnected
because the silicone
tubing can be
pinched when re-attaching the
hub to the syringe. Also
included is a gentian violet
ink pen for use in marking
the cornea.
The trephine assembly
consists of a blade that
is secured in a threaded
spoke adapter having a
thread pitch of 0.25mm.
The blade contains cross-hairs
to help the surgeon align
the blade with the
center of the desired
cut.
The spoke adapter screws
into a body subassembly
that consists of a threaded
plastic piece with finger
grips and a vacuum body
that is used to secure the
trephine onto the cornea
during cutting.
The spoke adapter
should not be removed from
the plastic body subassembly
as it can be difficult to
realign the threads.
Important: The
Barron Radial Vacuum trephine is
a disposable instrument that has
been sterilized with ethylene
oxide. It
should not be re-sterilized or
reused. Do not disassemble the
trephine or remove the hub from
the syringe. Each trephine
is tested prior to packaging and
is ready for use when it is
received by the surgeon.
Suggestions for Use
The Barron Radial Vacuum Trephine
should be used only by a licensed
physician who is familiar with corneal
transplant surgery and with the
use of this instrument. The
following instructions do not include
all of the procedural steps required
to perform corneal transplant surgery.
Dry the anterior corneal
surface with a cellulose sponge.
Mark the center of the
desired cut with a sterile
gentian violet marking pen.
Verify the blade diameter
that is stamped on
the top of the
plastic rim of the
blade assembly . Examine
the trephine under
an operating
microscope and turn
the white plastic spokes
on top of the blade
assembly until
the edge of the blade
is aligned with the
inner wall of the vacuum
chamber (zero position).
Retract the blade
a full revolution by
turning the white
plastic spokes on
top of the blade
assembly
(4 spokes)
to prevent the blade
from touching the surface
of the eye.
If the blade is not
retracted, vacuum will
not be obtained.
Moisten the anterior
corneal surface with balanced
salt solution.
Push in the plunger of the syringe
all the way and hold.
Grasp the white plastic
finger grips with
the thumb
and index finger of
the non-dominant hand
and while looking through
the center of the trephine
with the operating microscope,
align the cross hairs
with the centration
mark on the recipient
cornea.
Press the trephine
evenly on the anterior corneal
surface and release the plunger
of the syringe abruptly. Test
if vacuum has been obtained
and is adequately holding the
cornea against the trephine.
Note: If vacuum is
not obtained, check the
following:
Make sure the blade
was retracted one
complete revolution as
outlined in step #3
above.
A slightly uneven
cornea can prevent the
vacuum chamber
from making complete
contact with the cornea.
A small amount of viscoelastic applied to
the cornea usually
improves surface
contact.
Loose epithelium can
also prevent the
vacuum chamber
from making complete
contact with the cornea.
Remove any loose
epithelium and moisten
the anterior corneal
surface with balanced
salt solution.
Remember to release
the syringe plunger
abruptly while the
trephine is held firmly
against the surface of
the cornea. Grasping the
syringe with one hand
and placing the thumb on
the plunger will make a
quick release easy.
Avoid asperating fluid
into the silicone tubing
as doing so may block
the tubing.
Once vacuum has been
obtained, confirm that the trephine is
in the correct position and
wait approximately 30 seconds.
Stabilize the trephine by lightly
holding it with thumb and index
finger of the non-dominant hand.
Do not squeeze or tilt the trephine.
Excessive pressure on the
finger grips may prevent the
blade from rotating freely.
With the index finger of the dominant
hand, turn the spokes on top
of the blade assembly one
full revolution (4 spokes) clockwise
(as viewed from the top),
which returns the blade to zero position.
To commence cutting, advance
the blade by turning the
spokes clockwise. For each complete
revolution (4 spokes), the blade
is lowered 0.25 mm.
When the desired depth of
cut has been reached, release vacuum by pushing in
the plunger of the syringe.
Remove the trephine from the cornea.
For even suture placement,
dry the anterior corneal
surface with a cellulose
sponge and mark the 16 radial
impressions made by the
trephine with a gentian
violet marking pen.
CAUTION:
Once the cornea is perforated with
the trephine, the blade should not
be lowered further and the
trephine should immediately be removed
from the eye.
Note:
Some users have developed
their technique so that the
entire recipient cut is made
with the trephine. However,
this procedure should done with
extreme caution.
When cutting, hold the trephine
lightly between the thumb and
finger, and as low as possible.
Holding the trephine with excessive
force could cause the spoke
adapter and blade assembly to bind.
If the epithelium is loose
or bullous, most surgeons remove
it prior to application of the
trephine.
An example of the use
of the Barron Radial Vacuum
Trephine is shown in the
Flash Video at the right
.
If you don't have a Flash
player installed on your
computer you can download
a MPEG video (.mp4)
file by clicking
here
. (21.5MB file)
Color Code for Trephine Hubs
Color
Size
Brown
6.0 mm
Pink
6.5 mm
Green
7.0 mm
Light Blue
7.25 mm
Yellow
7.5 mm
White
7.75 mm
Dark Blue
8.0 mm
Red
8.25 mm
Gray
8.5 mm
Clear
8.75 mm
Orange
9.0 mm
The instructions for the Radial
Vacuum Trephine are available in
pdf format in English, French, German,
Italian, and Spanish. The
files require Adobe Reader which
can be downloaded if your browser
doesn't currently have a version
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