Instructions: Barron Radial Vacuum Trephines

Radial Vacuum Trephine
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Instructions for Barron Radial Vacuum Trephines

Radial Trephine Components

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.

Radial Trephine Parts

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.

  1. Dry the anterior corneal surface with a cellulose sponge. Mark the center of the desired cut with a sterile gentian violet marking pen.
  1. 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).
Radial at Zero Position
Radial Backed Off
  1. 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.
  1. Moisten the anterior corneal surface with balanced salt solution.
  2. Push in the plunger of the syringe all the way and hold.
  1. 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.
Radial Crosshairs
  1. 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.
  2. Note: If vacuum is not obtained, check the following:

    1. Make sure the blade was retracted one complete revolution as outlined in step #3 above.
    2. 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.
    3. 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.
    4. 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.
  3. Once vacuum has been obtained, confirm that the trephine is in the correct position and wait approximately 30 seconds.
  4. 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.
  5. 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.
  6. To commence cutting, advance the blade by turning the spokes clockwise. For each complete revolution (4 spokes), the blade is lowered 0.25 mm.
  7. 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.
  8. 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.
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.

  • 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 - Get Adobe Reader


Instructions in English INSTRUCTIONS FOR USE - In English
Instructions in French MANUEL D'UTILISATION - en Français
Instructions in German GEBRAUCHSANWEISUNG - auf Deutsch
Instructions in Italian GEBRAUCHSANWEISUNG - in Italiano
Instruction in Spanish INSTRUCCIONES DE USO - en Español