Iris Repair and Iris Prosthesis

Globe Pressurization

During iris repair, the globe needs to be pressurized to minimize bleeding and maintain normal anatomic relationships.

• Intact lens capsule diaphragm: OVD may be used.

• Open lens capsule diaphragm: infusion should be used.

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    A 23-g high-flow limbal infusion cannula maintains a small incision yet allows good fluid flow.

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    Avoid pars plana infusions, which create an unfavorable posterior-to-anterior flow gradient.

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    Infusion mechanism:

    • Active pump system: may push fluid too aggressively out of a wound.

    • Gravity feed is more forgiving.

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    For either type of infusion system, the intraocular pressure only needs to be at, or a little above, physiological pressures. High infusion pressures should be avoided for iris work because it can cause damage to iris caught in fluid flow out through an incision.

Sutures and Needles

• The standard suture material for iris repair is 10-0 polypropylene.

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    Excellent combination of strength and flexibility. In the anterior chamber, it degrades extremely slowly over many decades. In sclera, degradation is between 7 and 20 years.

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    If the transscleral 10-0 polypropylene passed through sclera for iris repair does degrade and break, it can be resutured. This rarely occurs, possibly because of the low tensile stress from the iris.

• Long curved transchamber needles (at least 13 mm long) are most commonly used.

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    The curve makes it easier to get from the limbus, down to the iris, and then back up to the opposite limbus.

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    A fine spatula side-cutting needle (e.g., Ethicon CTC-6L) makes the smallest orifice when passed through iris tissue; however, it is flimsy and so more difficult for some to control inside the eye.

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    A similar curved taper cut needle (e.g., Ethicon CIF-4) is typically more rigid, making it easier to control; but because of its continuous taper, it tends to drag on iris tissue and also make a larger orifice in the iris.

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    The authors generally prefer the fine spatula needle (e.g., Ethicon CTC-6L) because of the much greater flexibility in entry-exit locations and the low drag coefficient on iris tissue.

• Straight transchamber needles may also be used for iris suturing, but, for the needle to exit the eye, the entire needle must come anterior to the limbus plane, which automatically elevates the iris to that same plane, thereby stressing and deforming the iris enough that a tear at the iris root or suture site may occur.

Instrumentation

• An appropriate needle holder is essential for iris suturing.

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    A fine-tipped needle holder is needed, but because of how long the needles are, a stout hinge section is beneficial for a solid grip on the needle (e.g., Osher needle holder, Storz E3807 WO). One should avoid locking needle holders.

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    Titanium needle holders grasp stainless steel needles with greater friction on the stainless steel needles; however, design is more important than material.

• 23- or 25-gauge coaxial scissors is necessary to cut the suture tails on the knot in situ rather than dragging the knot, suture, and iris toward a limbal incision.

• Paracentesis blades of several types can be used. We advise making the paracenteses parallel to the iris.

• An iris support instrument can be useful during needle passage. Sometimes no support is required, but in other situations a coaxial intraocular forceps, iris reconstruction hook, intraocular lens (IOL) manipulator, or similar instrument will stabilize the iris and avoid putting undue stress on stromal tissue and the delicate iris root.

• Intraocular forceps with a curved shaft and 23- or 25-g size are required for tying certain intraocular knots. Reusable and disposable forceps are available from several manufacturers. Disposable 25-g vitreoretinal forceps may manually be bent at the shaft to make them useable in the anterior chamber.

• 23-, 25-, or 27-gauge bipolar diathermy probes can be extremely useful for adjusting pupil location and shape by contracting iris stroma. Disposable versions can be bent for improved ergonomics and iris access.

Vitreous Removal

If vitreous is near or around the iris that is in need of repair, then it should be removed before commencing iris surgery.

• Limited vitreous can be adequately removed through a limbal paracentesis with a guillotine cutter.

• With more vitreous, a single-port pars plana approach may be necessary. The pars plana is preferably accessed with a trocar and cannula system.

Pharmacologic Agents

• If pupil work is planned, then avoiding either preoperative dilating or constricting drops is advisable (unless combined cataract or IOL procedure is planned).

• For iridodialysis or oversew techniques, preoperative pilocarpine puts the tissue on stretch and makes repair more facile.

• Having an intraocular miotic available during surgery is often useful.

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    Acetylcholine works more quickly and avoids excessively strong constriction of the sphincter muscle. Instillation may be repeated, if need be.

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    Carbachol will also achieve constriction but should be used sparingly because of the tendency to produce exaggerated pupil constriction. Excessive sphincter contraction from carbachol may make it more difficult for the surgeon to intraoperatively assess the adequacy of iris repairs.

Clear Crystalline Lens

Iris repair in the presence of a noncataractous crystalline lens is a high-stakes undertaking. Even subtle bumps to the lens may cause a cataract to form.

• A dispersive OVD has an increased chance of causing a feathery subanterior capsular cataract, even during the case. This tendency is less with hyaluronate.

• Very experienced iris surgeons sometimes (but rarely) offer iris reconstruction in young patients with disabling photic symptoms. Thorough counseling is mandatory because cataract surgery may be needed during the case or soon after. An appropriate IOL should be available.