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Iridectomy Repairing The IrisIn the age of modern anterior segment surgery, we have the skills for more sophisticated iris repair.Michael E. Snyder, MD Note: Many images in this article had to be omitted in the interest of downloading speed. Please refer to October's Review of Ophthalmology magazine for the complete article. Abnormal Irides An abnormal iris can be acquired or congenital. Traumatic and surgical origins most commonly account for an irregular pupil, although other less common conditions, such as herpes simplex virus, herpes zoster ophthalmicus, uveitis and irido-corneal-endothelial (ICE) syndromes, may also lead to iris damage. Congenital etiologies include aniridia, Reiger’s anomaly and other anterior segment dysgeneses. Abnormal pupils affect patients in several ways, including photophobia and glare. These patients often describe discomfort or difficulty in brightly lit areas, such as supermarkets, or on sunny days. Typically, they report that sunglasses do not alleviate their symptoms either outside or indoors. Edge glare from an exposed intraocular lens optic margin can elicit similar complaints and may induce disturbing crescents, arcs of light, “tails” on lights and other optical aberrations. Rarely, an irregular pupil may induce an undesired refractive effect. Since the visual axis usually goes through the geometric center of the pupil, the visual axis-corneal intercept may be abnormally placed  through an area of irregular corneal topography. I saw one such
case following trauma in a patient with a previous RK. The sector-like iris
defect deflected the visual axis though the elbow of the patient’s RK
incisions, inducing a 3-D myopic shift. When his iris was repaired, his
refraction returned to plano (See Case 1, page 144). Figure 1. A long, curved needle is passed via a paracentesis (1) and the proximal iris leaflet is engaged (2), followed by the distal iris leaflet (3). The needle is then passed out the peripheral cornea (4). An abnormal pupil may also have deleterious psychosocial effects. As a society, we place a psychic premium on the appearance of the eyes. It is common for people to make instant judgments about others based on how their eyes look. A shifty gaze, for example, may be interpreted as dishonest. If people are uncomfortable looking into the eyes of a person with an abnormal iris, that can play an important role in that individual’s interpersonal interactions and, perhaps, affect his self-esteem. Recently, one retired patient said he was sure that his irregular pupil hampered his advancement in the corporate workplace. Often, patients may be reluctant or embarrassed to proffer such concerns unless specifically solicited, even though psychosocial issues may cause them significant distress. Surgical Planning Like most intraocular procedures, repairing a damaged iris requires preoperative planning and meticulous technique. With careful attention to detail and basic principles, you can master the art of iris repair. Preoperatively, you must determine whether there is sufficient iris tissue remaining to achieve the desired goals. It is often difficult to assess how much tissue is present because the iris stroma may be contracted or rolled over. Careful examination and review of prior operative notes are helpful in determining whether tissue has been removed. Typically, there is more iris present than you might think based on slit-lamp examination. Furthermore, iris tissue is usually very stretchable and can cover larger areas than you might initially anticipate. Usually, if the patient retains two-thirds or more of normal iris tissue, surgical repair can produce a good functional and anatomic result. For cases in which large amounts of iris tissue is absent, artificial iris diaphragms, overlapping rings or sectoral implants may be a more appropriate option to augment the remaining native iris tissue.
Principles of Iris Repair The basic principles of iris repair are fairly straightforward. First, instillation of a miotic agent, such as acetylcholine or carbachol, puts the iris stroma on maximal stretch, increasing the surface area. Intracameral manipulations should be performed under viscoelastic agents to prevent chamber volatility, iris stretching and corneal endothelial damage. When choosing your viscoelastic agent, remember that you may be removing it manually through a small incision. Highly retentive agents may be difficult to remove without automated irrigation and aspiration, while retained bits of overly viscous materials can cause a significant postoperative intraocular pressure rise. The very soft and friable consistency of the iris demands an atraumatic technique. Often, posterior or peripheral anterior synechiae prevent proper mobilization of the iris leaflets. Therefore, gentle blunt or sharp synechiolysis may be the first step in repair. When the sphincter is involved in the injury or damage, reapposing the severed pupil margin establishes a central pupil and creates a more taut iris diaphragm, facilitating further steps. Because patients may develop glare symptoms when the optic margin of an implant lens is exposed, the repaired iris leaflets should cover all IOL edges. When an implant placement or exchange is performed coincident with iris repair, a larger optic implant may facilitate this task. Suture Placement Suture and needle choices are up to the surgeon’s preference. With a long track record in the anterior segment, the prolene suture appears resistant to hydrolysis in the anterior chamber and, therefore, may be a better choice than nylon. I prefer to use a long, curved needle with a narrow bore and very sharp tip (10-0 prolene on CTC needle, Ethicon, Inc. (Somerville, NJ). The needle enters the anterior chamber via a conveniently placed paracentesis site. The paracentesis should be large enough to allow easy ingress of a Kuglen hook. Take special care to avoid catching any corneal fibers as the needle passes through the paracentesis tract. The sharp-tipped needle passes through the iris with a minimum of countertraction and minimal iris tearing. The long, curved shape permits passage of the needle in a closed-chamber fashion through a paracentesis. The proximal iris leaflet is engaged by the needle tip, then the distal iris leaflet. The needle is then passed out through the peripheral cornea (See Figure 1). Suture Tying Tying the suture with the sliding knot technique (introduced to ophthalmology by Steven Seipser, MD) minimizes iris traction. This technique allows the knot to slide into the anterior chamber without pulling iris tissue to the wound margin and without cumbersome intracameral knot-tying maneuvers. Once the suture has been passed, place a Kuglen hook through the initial paracentesis tract, engage the suture just beyond the distal iris pass and draw a loop of suture out through the paracentesis site. Maintaining proper orientation of the sutures is of utmost importance in creating a knot. The orientation should be: 1) trailing suture strand; 2) part of loop from distal iris pass and; 3) part of loop exiting peripheral cornea. If the loop folds over and changes the relative position of 2 and 3, a twist occurs instead of the intended knot. Pass the trailing suture around the middle arm of the loop twice (See Figure 2). Then gently draw together the trailing strand and the exited strand on the opposite side of the eye, pulling the two iris leaflets together and creating the first throw of a knot (See Figure 3). Retrieve the suture loop a second time for a single locking throw and trim the knot. Case 1: Repair of Sector Iridotomy A 35-year-old stockbroker had a 12-cut radial keratotomy 12 years previously. He suffered an injury resulting in traumatic cataract and iris prolapse through the superior radial incision. Cataract surgery with a sector iridectomy left him with persistent, disabling implant edge glare and a resultant -3 D. He elected iris repair alone since glare was his primary concern (See Figure 4). After iris repair, his glare resolved and the pupil was round, mobile, central and symmetrical. Because his visual axis was recentered from the elbow of his RK to the corneal apex, his myopia also resolved. The patient conceded his further delight that he no longer felt people were staring at him like he was “shifty-eyed,” and he lost his nickname of “the coach with the cat eye” given to him by his son’s little league team. Case 2: Iris Imbrication A 78-year-old man came to our practice because he was very dissatisfied with his extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens procedure performed elsewhere. He presented with intolerable glare and photosensitivity due to post-ECCE iris damage with prominent mydriasis. Posterior synechiolysis freed the iris from the underlying capsule and several sutures were placed to imbricate the atonic iris margin until a more physiologic, smaller pupillary aperture was achieved (See Figure 5). The patient’s glare and photosensitivity resolved completely.
Case 3: Iris Imbrication A 42-year-old man had a traumatic cataract with sectoral iris margin atrophy. I repaired his iris by imbricating the iris margin inferonasally at the juncture between atrophic and healthy-appearing sphincter muscle. Following the closure of the area of visible sectoral sphincter atrophy, the pupillary aperture remained larger than desired and an additional imbrication was performed inferotemporally (See Figure 6). Repair of Iridodialysis Iridodialysis and iris repair share similar principles and some similar techniques, with a few caveats. Use a double-armed suture. In a similar closed-chamber approach, I engage the peripheral iris margin with the first needle tip and pass the suture through the scleral wall at the level of the iris root. I pass the second needle through the same paracentesis and engage the peripheral iris root about one to two clock hours away. The second needle is similarly passed out the sclera and the suture is tightened and tied externally, drawing the peripheral iris to the scleral wall. The knot is trimmed and rotated internally (See Figure 7). Iris Implants When significant amounts of iris tissue are damaged or missing, iris repair may be impossible. In these eyes, artificial iris implants can augment the iris diaphragm, thereby reducing photophobia and glare. A variety of artificial implant designs are available in Europe and elsewhere, though currently none are Food and Drug Administration approved for use in the United States. The currently manufactured iris implants come in five categories:
The products from Morcher are manufactured from black PMMA. Since black PMMA is more brittle than standard PMMA, it requires careful handling to reduce haptic breakage. Ophtec’s products are made of Perspex in blue, green and brown. The currently manufactured products can markedly reduce patients’ glare and photophobia. The appropriate implant choice is often highly specific to a given patient’s anterior segment anatomy. The optimal outer and inner diameters of iris implants, the optimal design, materials and relations to an implanted optic have yet to be definitively determined. I believe that continued evolutions in design and, hopefully, an increasingly facile, less costly FDA approval process will spur both iris implant development and availability. We are enthusiastic about our experiences with these iris-augmenting implants at the Cincinnati Eye Institute, and anticipate that further study and innovation will provide implants which are increasingly effective and cosmetically acceptable. With meticulous surgical technique, most patients with an abnormal pupil can benefit both functionally and psychosocially from iris reconstruction. For those patients whose native iris is damaged beyond reasonable repair, artificial iris implants and segments provide an excellent option. Dr. Snyder practices at the Cincinnati Eye Institute. He has no financial interest in the products mentioned. |
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