The torque antitorque suture pattern (figure A), originally developed by Dr Richard
Troutman, has many advantages over other suture techniques in corneal transplantation.
First, the net of sutures overlying the graft edge provides protection against the
outward intraocular pressure assuring against graft edge lift. Second, the arrangement
of the pattern provides direct compression across the wound, causing the cornea
inside the suture bites to lift upwards and causing the central cornea to flatten
for about a month. During this time, the thin 10-0 nylon sutures “cheeswire” into
the cornea, causing the flat central cornea to steepen and provide a stable environment
for wound healing. Sutures are left in place for one year, based on an average time
of corneal wound healing. If excessive astigmatism is a problem, additional sutures
are added rather than the common practice of removing sutures early to provide (temporary)
The standard PK begins with a trephination centered on the pupil 8mm in diameter,
eccentric grafts will cause astigmatism. The donor cornea is prepared with a 8.5mm
trephine and placed into position with a single interrupted suture placed at 12 o”clock..
The second interrupted suture is placed 180 degrees away at 6 o’clock taking care
to place the suture in such a manner that spacing on both sides of the host opening
are equally spaced. Using a single suture, 4 additional bites are taken equidistantly
to complete the six interrupted “stay” sutures holding the graft in place of the
application of the running sutures (figure B). These are then tied off using the
slip knot. All sutures should be tied tightly and at this point the cornea should
be watertight. The anterior chamber can be reformed at this point.
The first running suture can then be placed, with 12 or 18 bites as the surgeon pleases,
in a clockwise direction. I have found that 18 bites results in a stronger wound
closure and less postoperative astigmatism. All bites are made in a radial fashion,
perpendicular to the graft wound. The running suture is tied with a slip knot and
tightened “hand over hand”, finished with 2 overhand throws and the knot is buried.
At this point a curious observation can be made (figure C). The running suture has
twisted the donor graft clockwise so that even the originally radial sutures are
no longer radial. If the PK was stopped at this point, the forced across the graft
wound would be twisting rather than radial and graft edge lift and/or large amounts
of astigmatism would likely result.
The answer is to add a second suture in a counter-clockwise direction, making each
bite parallel to the rotated bites of the previous pass. When this running suture
is tied with a slip knot and tightened, the graft will rotate counterclockwise restoring
all suture bites to a radial configuration, perpendicular to the graft margin (figure
D). Thus the forces across the wound will compress the tissue allowing optimal wound
healing. Additionally, the original interrupted sutures will be loose and are easily
Imagine that the second running suture were placed in the same clockwise direction
as the first running suture. The donor graft would be further rotated and the wound
healing would be further compromised.
Click on the figures above to see larger clinical views of the incision creation.
Corneal Astigmatism: Etiology, Prevention, and Management, CV Mosby, published 1992,
Richard Troutman, M.D., Kurt Buzard, M.D.