Instructions for Barron Radial Vacuum Trephines®

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
  1. Dry the anterior corneal surface with a cellulose sponge. Mark the center of the desired cut on the recipient cornea with a sterile gentian violet marking pen.

2. Verify the blade diameter that is marked on the white plastic spoked rim. Examine the trephine under the operating microscope and turn the white plastic spokes on top of the blade assembly clockwise until the edge of the blade is aligned with the inner wall of the vacuum chamber; this is the ‘reference’ position.

  1. Retract the blade by turning the spokes of the blade assembly at least two full rotations (8 spokes) counterclockwise. If the blade is not retracted vacuum will not be obtained.
  2. Moisten the anterior corneal surface with a balanced salt solution.
  3. 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 crosshairs with the centration mark on the recipient cornea.
  2. 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:
    1. Make sure the blade was retracted at least two full revolutions 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 aspirating 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 of the blade assembly clockwise until the blade contacts the cornea. Note that the shape of the cornea and the precision of setting the reference position will determine the amount of clockwise movement needed to contact the cornea.
  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.

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.


  • 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 body subassembly to bind.
  • If the epithelium is loose or bullous, most surgeons remove it prior to application of the trephine.

Color Code for Trephine Hubs
Brown6.0 mm
Pink6.5 mm
Green7.0 mm
Light Blue7.25 mm
Yellow7.5 mm
White7.75 mm
Dark Blue8.0 mm
Red8.25 mm
Gray8.5 mm
Clear8.75 mm
Orange9.0 mm

Barron Precision Instruments, LLC is now a part of Corza Medical. Learn more about the acquisition at