Knowing Iris Repair: Pupilloplasty

McCannel suture 

Introduced in 1976, the McCannel suture technique uses a 10-0 prolene suture on a long needle introduced through the limbus and passed through the approximated first and second iris edges and out the limbus on the other side. The suture on either side of the iris is then retrieved with a Sinskey or Kuglen hook passed through a paracentesis created between the two limbal sites and a single or double knot is slowly and gently tightened to approximate the iris edges. Further knots are then thrown. The McCannel suture has the disadvantage of traction on the iris towards the paracentesis while tighten­ing the knots that may not be tight enough.

Siepser sliding knot

Siepser modified the McCannel suture in 1994 by introduc­ing the sliding knot to make tightening easier and less trau­matic to the iris. It gives a tighter knot and better approxi­mation of the iris. Here, the knot is tied outside the eye and then drawn in to be tightened over the iris.

A long, thin, curved needle on a 10-0 prolene suture is passed from the limbus through the first and second limbs of the iris and then railroaded into a 26-gauge needle passed into the anterior chamber (AC) through a limbal paracentesis and thus brought out. A Sinskey or Kuglen hook is passed through the paracentesis and the initial length of the suture before the first pass through the iris is hooked and brought out through the paracentesis in the form of a loop. The trailing segment is then passed over and under one side of the retrieved loop to create the knot.

Osher’s modification

Professor Robert Osher’s modification of the Siepser knot created two consecutive slip knots around a carefully untwisted, retrieved suture loop—the first one tightened after passing the cut end twice around the strand emanat­ing from the iris, followed by retrieval of the loop again to create one locking knot.

Condon’s modification

Dr Garry Condon modified the Siepser knot by using forceps to wrap one side of the loop around the suture, just as in a simple double throw knot.

Single-pass, four-throw pupilloplasty

Dr Amar Agarwal modified this further by using only a single pass and four throws. A paracentesis is created at the site through which the needle will emerge after the second iris pass. Any pre-existing paracentesis sufficiently close may also be used instead.

The first limb of the iris to appose is held with a micro­forceps that passes through this paracentesis. A 10-0 prolene suture on a long, thin, curved CIF-4 needle or a straight STC-6 needle is passed trans-limbally through the iris root, suffi­ciently close to the edge to prevent undue iris bunching but with sufficient gap to prevent cheese-wiring. The needle is then carefully released and allowed to rest freely. Followed by a 30-gauge needle passed through the paracentesis, taking care not to engage corneal tissue. 

The second limb of the iris is held firmly by a microfor­ceps passed through a second paracentesis, and the 30-gauge needle is passed through the iris, again close to its edge. The needle on the 10-0 prolene suture is docked into this 30-gauge needle and railroaded out through the paracentesis. A Kuglen or Sinskey hook draws a loop of the initial pass of the suture out through the paracentesis. The free end of the suture is then cut and looped four times around the externalized loop. The two ends of the suture on either side of the limbus are then pulled in opposite directions—this internalizes the knot and tightens it over the iris, bringing the two limbs of the iris together. Advantages include ease of surgery and the ability to use either limb of the externalized loop.

Pinhole pupilloplasty (PPP)

As described by Dr Agarwal, the pupil is made pinhole sized to remove the effect of HOAs and improve visual acuity in eyes with high amounts of irregular astigmatism.

Open-sky pupilloplasty

A pupilloplasty is often needed in combination with a pen­etrating keratoplasty. In this case, an open-sky pupilloplas­ty may easily be done. A short, curved needle on a 10-0 nylon suture is often easier to pass than the long, curved needle attached to the 10-0 prolene suture. Care should be taken to avoid excess pulling to avoid any tug on the ciliary body in the open-sky state.

Complications

There must be enough stretch in the iris to bring the limbs together from either side. If pulled without sufficient laxity for the two limbs to appose, the suture can cheese-wire through the iris, or the iris can detach from its root, creating an iridodialysis and bleeding into the AC. Excessive stretch can also result in iris stromal tears, iris hole creation, etc. Extensive manipulation can result in postoperative iritis.

Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at dr_soosanj@hotmail.com.