Minimally Invasive Iris Surgery

7.1 Instrumentation

In addition to standard instrumentation commonly used in ophthalmic microsurgery, specialized instrumentation is invaluable. The surgeon often needs instruments such as forceps, scissors, and needle holders that can be inserted and maneuvered through small incisions. Vitreoretinal instruments designed for the pars plana generally meet these needs. For the anterior segment, Iqbal “Ike” Ahmed has designed a set of anterior segment instruments for the anterior segment, similar to vitreo-retinal instruments in their coaxial action. These instruments are available from MicroSurgical Technologies (MST) of Redmond, WA. The assorted end pieces are designed to be interchanged from common handles, reducing total cost.

Minimally invasive, closed chamber iris suturing can be performed with small needles manipulated inside the anterior chamber by microinstruments or with long needles that pass across the anterior chamber, controlled by a needle holder that remains external to the anterior chamber. In the case of a small needle, a noncutting taper needle is preferred, as it will not create a hole in the iris as it passes. These needles are typically created for use by vascular surgeons. An example is the Ethicon BV-100.

Examples of longer needles available with 10-0 polypropylene suture material are the very thin and long CTC-6 (curved) and STC-6 (straight) needles and the thicker CIF-4 needle, all made by Ethicon. Alcon, SharpPoint, and other suture manufacturers have their own similar needles with proprietary designations.

Any suturing of the iris should employ a suture that does notbiodegrade.Mostcommonly,polypropylene(Prolene) is used, although monofilament polyester (Mersilene) is acceptable. Nylon will biodegrade over several years in the anterior chamber and therefore is usually not a good choice. 10-0 caliber is adequate; the extra strength of 9-0 is not needed, as the iris tissue will typically tear if force exceeding the tensile strength of 10-0 polypropylene is needed to draw the iris edges together.

R. F. Steinert

University of California, The Gavin Herbert Eye Institute, 118 Med Surge1, Irvine, CA 92697-4375, USA

email: roger@drsteinert.com

Although iris deformities have an infinite number of possible configurations, the basic principles of surgical repair can be summarized in a few basic techniques.

7.3.1 Mobilization

The first principle is to free up and mobilize as much iris tissue as possible. Synechia to the cataract or capsule should be bluntly dissected. Most iridocapsular adhesions are strongly attached only at the sphincter edge. Often there is some proliferation of iris pigment epithelium from the posterior iris surface to the capsule involving the more peripheral iris, but these adhesions

are weak and can be easily separated with an instrument such as a cyclodialysis spatula or a cannula with viscoelastic agent.

If iridocapsular adhesions cannot be bluntly dissected, then careful excision with a scissors or blade should be performed, preserving as much iris tissue as possible by taking care not to excise any iris tissue that is salvageable.

After freeing up all iridocapsular adhesions, the surgeon should then release any peripheral adhesions. Peripheral anterior synechia usually can be released with traction using forceps or a pointed hook such as a Sinskey hook or Osher Y hook or by sweeping maneuvers with a spatula. In addition, inflammation sometimes causes the iris stroma to form adhesions internally, causing contraction of the iris in a manner similar to accordion pleats. Again, gentle traction can release many of these adhesions and produce a surprising amount of iris tissue necessary for the subsequent repair.

7.3.2Intraocular Suturing and Knot Tying

The second fundamental principle is the method for suturing iris and tying knots within the eye. Often the knot is central, and traction to bring the iris with the knot to a limbal incision will damage the iris repair. Figure 7.1 illustrates the basic technique for passing the suture into the anterior chamber via a paracentesis, through a radially oriented iris defect, and then out through the peripheral cornea on the opposite side of the paracentesis.

A flaccid iris and a knot close to a wound may allow the surgeon to tie the knot at the limbus without undue iris damage. Successful completion of many cases of iris reconstruction requires that no additional traction be placed on the iris, however. The knot must be advanced into the eye and tied internally. One method to accomplish a knot deep inside the anterior chamber is to form the knot loop externally and then use a hook

Fig. 7.1 (a) Long needle enters through a paracentesis, across the iris defect, and exits by puncturing through the peripheral cornea. (b) Hook such as a Kuglen hook retrieves a loop of the distal arm of the suture, making sure that the needle end of the suture remains external to the eye. (c) Loop is now external through the paracentesis. (d) Proximal end of the suture is

wrapped around the suture loop twice, creating one throw of what will become the knot. (e) Tension on each end of the suture draws the knot into the eye and tightens it. (f) After four throws, the suture ends are cut with a thin sharp knife such as a wheeler blade.

such as a Kuglen hook to advance the loop into the eye and make it snug. The procedure is repeated 3 or 4 times, achieving a secure knot at completion. The disadvantage of this technique is that it requires a skilled assistant, as it is necessary to maintain gentle traction on each of the suture ends while simultaneously advancing the knot with the hook. Three skilled hands are therefore needed.

Figure 7.1 illustrates an alternative two-handed technique popularized by Stephen Siepser. In this variation, the knot is tied by passing loops externally, but the two ends of the suture can then be tightened, which draws the knot internally into the eye. This technique is elegant and does not require the third hand of a skilled assistant. A second throw is typically placed. In the original description by Seipser, the second throw creates a “granny” knot. Robert Osher teaches a true locking knot in which the second throw is passed either in mirror image of suture orientation or in the opposite direction around the suture loop to create a more

“square” locking knot [5]. Once the knot is tied, the suture may be cut using microscissors through an unenlarged paracentesis, or with Vannas scissors through a slightly enlarged limbal incision.

7.3.3 Reattachment of Iris to Sclera

The third principle is the technique for repair of a peripheral iris defect with the use of horizontal mattress sutures. A double-armed suture is employed. The mattress suture brings the iris back to its origin, if possible (Fig. 7.2), or closes a peripheral defect using available adjacent iris tissue (Fig. 7.3a, b). The knot is tied externally, but then rotated below the surface so that only a smooth loop of external suture remains, to be covered subsequently by a conjunctival flap. By using this technique of suture rotation and burying the knot, only a smooth loop of suture material remains.

Fig. 7.2 (a, b) Iridodialysis is repaired with one or more mattress sutures of double-armed 10-0 polypropylene sutures tied externally under a conjunctival flap. Both arms of the polypropylene suture are introduced through a paracentesis opening on the opposite side of the anterior chamber. The dialyzed edge of iris is engaged by each needle in turn, and the needle is passed

through the sclera. (c) Mattress suture is tied. (d) Knot is rotated below the surface of the sclera, preventing later suture erosion through the conjunctiva. (e) Conjunctival flap is then closed over the polypropylene mattress suture with corner sutures of 8-0 Vicryl or other absorbable suture material.

Fig. 7.3 (a) Conjunctival flap is recessed in the area of a sector iris defect. (b) Horizontal mattress sutures bring midperipheral iris tissue into the basal area without iris. (c) Interrupted sutures

close the midperipheral space. (d–f) “Sphincterotomies” in the central zone create a new pupillary aperture.

A scleral flap does not need to be dissected, and conjunctiva alone provides adequate coverage of the suture material. Alternatively, if it is desired that both suture material and knot lie below the scleral surface, then creating a scleral groove with a beaver blade before placement of the sutures can be helpful. This allows the suture material to lie in a trench beneath the scleral surface when the knot is tied. The knot can similarly be rotated into the sclera. A large iridodialysis will require several adjacent horizontal mattress sutures. The size of each suture “bite” of iris should be about 1.5 clock hours.

A large defect may require a combination of these techniques (see Fig. 7.3). Typically, the repair begins by using horizontal mattress sutures to create as much

coverage of the peripheral and midperipheral cornea as possible (see Fig. 7.3a, b). Often this results in a distortion of the pupil itself (see Fig. 7.3c). A new pupil is constructed by judicious incisions in the iris and placement of additional sutures (see Fig. 7.3c–f). The iris is highly visible in some individuals and often important to the patient cosmetically as well as optically.

In general, the surgeon should err on the side of leaving a pupil too small rather than too big. Postoperatively, a surgeon can use the neodymium:yttrium-aluminum- garnet (Nd:YAG) laser to expand the pupil by performing sphincterotomies with Nd:YAG laser pulses. The technique is similar to performing peripheral iridectomies with the Nd:YAG laser. A focusing contact lens is helpful. The laser setting is typically 6 mJ.