Tutorial
Introduction
Abnormal Iris
Examination
Surgical Planning
Principles of Iris Repair
Suture Placement
Suture Tying
Cerclage Sutures
Case 1: Repair of Sector Iridotomy
Case 2: Iris Imbrication
Repair of Iridodialysis
Case 3: Iridodialysis and Iris Imbrication
Case 4: Multiple Sphincterotomies
Iris Implants
Slides
Repairing and Replacing the Iris
Michael E. Snyder, MD
With early intracapsular surgical procedures, ophthalmologists purposefully created large superior sector defects. Often, iris tissue became incarcerated in a corneal or scleral wound, thereby, creating marked corectopia. One or more large peripheral iridectomies can result in pseudopolycoria. Little attention was paid to glare complaints or optical aberrations in that era. In iridencleisis procedures to treat glaucoma, the iris was intentionally pulled through a scleral wound, creating marked pupillary distortion. As extracapsular cataract extraction (ECCE) gained popularity, the iris would occasionally prolapse through a limbal incision during ECCE.
In this enlightened age of small-incision "closed system" anterior segment surgery, surgeons have gained increased surgical control over the intraocular environment and have developed the skills needed for more sophisticated iris repair. Simultaneously, surgeons have become increasingly attentive to glare and photic complaints from both cataract and refractive surgery patients. This confluence of increased awareness and increased abilities has set the stage for a new era of iris surgery.
An abnormal iris can be either acquired or congenital. Traumatic and surgical origins are the most common reasons for an irregular pupil; however, other less common conditions such as herpes simplex virus, herpes zoster ophthalmicus, uveitis, and iridocorneal endothelial (ICE) syndromes may also lead to iris damage. Congenital causes include aniridia, Reiger’s anomaly, and other anterior segment dysgeneses.
Abnormal pupils may affect patients in several ways. Patients with an abnormal iris will commonly complain of photophobia and glare. An enlarged pupil may allow excess light to pass into the eye causing photophobia. These patients will often describe discomfort or difficulty keeping their eyes open in brightly lit rooms on bright sunny days. Typically, they report that sunglasses do not alleviate symptoms either outside or indoors. Edge glare from an exposed IOL optic margin may elicit similar patient complaints and may induce disturbing crescents, arcs of light, "tails" on lights, and other optical aberrations.
In patients with ocular or oculocutaneous albinism, the anatomic iris structure may be intact, yet the lack of pigment in the posterior iris epithelium can cause significant photophobia.
Rarely, an irregular pupil may induce an undesired refractive effect. Because the visual axis will usually go through the geometric center of the pupil, the visual axis-corneal intercept may be abnormally placed through an area of irregular corneal topography in a multifocal cornea following refractive surgery or corneal transplant. In a patient with a previous radial keratotomy (RK) who experienced ocular trauma, the sector-like iris defect deflected the visual axis through the elbow of the RK incisions, inducing a 3-D myopic shift. When the iris was repaired, the refraction returned to plano.
An abnormal pupil or iris may elicit psychosocial effects. We as a society 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 who has an abnormal iris, that can play an important role in that individual’s interpersonal interactions and, perhaps, even affect their self-esteem. One retired executive confided to me that he was sure his irregular pupil had hampered his advancement in the corporate workplace. Often, patients may be reluctant or embarrassed to proffer such concerns unless specifically solicited. The psychosocial effects of an abnormally appearing eye may induce significant distress and should not be underestimated or trivialized.
When evaluating a patient with an abnormal iris, surgeons must consider several different facets of iris structure and function. First we study the appearance of the iris contours in the non-dilated state, making note of the anatomic status and function of the sphincter, holes, tears, or tissue removed. The quality of the iris stroma is assessed by observing the thickness and the anatomy of the stromal cords. Some patterns may indicate dysgenesis, while others may show prior injury. When the stromal cords approach the pupil margin tangentially, this usually indicates prior sphincter damage. The degree of stromal pigmentation or any heterochromia can be seen best by oblique illumination, while pigment epithelial defects can be detected better with retroillumination.
Like all intraocular procedures, repairing a damaged iris requires preoperative planning and meticulous technique.
Preoperatively, the surgeon 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 when the pupil is damaged, the iris stroma may be contracted or rolled over. Careful examination and review of previous operative notes can be helpful in determining whether tissue has been removed. Typically, there is more iris present than can be observed under the slit lamp. Also, iris tissue is usually stretchable and can cover larger areas than might initially be anticipated. As a rule, if a patient has 67% to 75% or more of normal iris tissue, a good functional and anatomic result can usually be obtained by surgical repair. For cases in which large amounts of iris tissue are absent, artificial iris diaphragms, overlapping rings, or sectoral implants may be a more appropriate option to augment the remaining iris tissue.
The appropriate technique must be selected for each case. Often, instillation of a miotic agent (such as acetylcholine or carbachol) will put the iris stroma on maximal stretch, increasing the surface area and facilitating the closure of peripheral defects. In some instances, however, minimizing the contraction of the sphincter would be more helpful, for example, in repair of multiple sphincterotomies.
Intracameral manipulations should be performed under viscoelastic agents to prevent chamber volatility, iris stretching, and corneal endothelial damage. When choosing a viscoelastic agent, remember that it may be removed manually through a small incision. Highly retentive agents may be difficult to remove without automated irrigation and aspiration. Retained bits of overly viscous materials can result in a significant postoperative intraocular pressure rise.
The very soft and friable consistency of the iris dictates the need for a particularly atraumatic technique. Often, posterior synechiae or peripheral anterior synechiae will prevent proper mobilization of the iris leaflets. Therefore, gentle blunt or sharp synechotomy may be the first step in repair.
When the sphincter is involved in the injury or damage, re-apposing the severed pupil margin first will establish a central pupil and create a more taut iris diaphragm, thereby facilitating further steps.
Because patients may develop glare symptoms when the optic margin of an IOL 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 and needle choices are a matter of surgeon preference.
Prolene sutures have a long track record in the anterior segment and do not
appear to be vulnerable to hydrolysis in the anterior chamber. Therefore,
prolene sutures 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, 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. Special care should be taken to avoid
catching any corneal fibers as the needle passes through the paracentesis
tract. The sharp-tipped needle passes through the iris with minimal
countertraction and iris tearing. The long, curved shape permits passage of the
needle in a closed-chamber fashion via a paracentesis site. The proximal iris
leaflet is engaged by the needle tip, then the distal iris leaflet. The needle
is then passed out of the peripheral cornea (Slide
1).
Iris traction is minimized by tying the suture with the
sliding knot technique, which was introduced by Steven Seipser, MD. 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, a Kuglen (or similar hook) placed
through the initial paracentesis tract engages the suture just beyond the
distal iris pass. A loop of suture is drawn out of the paracentesis site.
Maintaining proper orientation of the sutures is important in creating a knot.
The orientation should be: (1) trailing suture strand, (2) part of loop from
distal iris pass, and (3) part of the loop exiting the peripheral cornea. If
the loop becomes folded over, a twist will occur instead of the intended knot.
The trailing suture is passed around the middle arm of the loop twice (Slide 2). The trailing strand and the exited strand on
the opposite site of the eye are then gently drawn together, pulling the two
iris leaflets together and creating the first throw of a knot (Slide 3). The suture loop is retrieved a second time for
a single locking throw and the knot is trimmed (Video).
For mydriatic pupils, imbricating sutures may be placed to
reduce the pupillary circumference. Alternatively, when the iris stroma retains
integrity, a cerclage suture can be placed. In this technique, a long, curved,
sharp needle with 10-0 prolene suture is placed via a corneal wound and woven
frequently in and out of the iris stroma just peripheral to the pupil margin,
taking many small bites (Slide 4A and
Slide 4B). Ideally, the suture will pass through
partial thickness stroma throughout most of its course, leading to a more
uniform appearance to the pupil margin. In a very thin or friable iris, the
suture may weave in and out of the iris stroma with full-thickness, through and
through bites, though this leads to a rosette-like appearance of the pupil
margin. This appearance can be minimized by taking the bites approximately 0.5
mm further peripheral to the margin. The cosmetic appearance also improves with
increasing numbers of bites.
After the first several bites, the needle exits the cornea by engaging it in the bore of a 27-gauge cannula placed via a paracentesis. The needle is reintroduced, taking care not to catch any corneal fibers in the paracentesis tract, and several more bites are taken for a few more clock hours. This sequence is serially repeated until the entire pupillary circumference has been engaged, then the knot is tightened to achieve the desired pupil size (Video).
A gentle touch must be used in suture passage and tying, since attempts to pass sutures through a thin or friable iris stroma can result in cheesewiring. In such cases, imbricating sutures may be more appropriate.
Case 1: Repair of Sector Iridotomy
A 35-year-old stock broker had a 12-cut RK 12 years
previously. He suffered an injury resulting in a traumatic cataract and iris
prolapse through the superior radial incision. After cataract surgery with a
sector iridectomy, the patient experienced persistent, disabling IOL edge glare
and 3-D of myopia. He elected iris repair alone because glare was the
patient’s primary concern (Slide 5).
After iris repair, the edge glare resolved and the pupil was round, mobile, central, and symmetrical. As the visual axis was recentered from the elbow of the radial keratotomy to the corneal apex, the myopia also resolved. With prompting, the patient conceded his satisfaction in that he no longer felt people staring at him like he was "shifty-eyed."
A 78-year-old man came to our practice because he was dissatisfied with his previous ECCE and posterior chamber IOL procedure performed elsewhere. His complaints were intolerable glare and photosensitivity due to post ECCE iris damage with prominent mydriasis. Posterior synechotomy liberated 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 (Slide 6). The patient’s glare and photosensitivity resolved completely.
Iridodialysis and iris repair share similar principles and
similar techniques with a few caveats. A double-armed suture is required. 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. The second needle is passed through the same paracentesis and
the peripheral iris root is engaged about 1 to 2 clock hours away. The second
needle is similarly passed out of the sclera and the suture is snugged and tied
externally, drawing the peripheral iris to the scleral wall. The knot is
trimmed and rotated internally (Slide 7).
Case 3: Iridodialysis and Iris Imbrication
A 45-year-old man was struck in his right eye with a rock
while mowing his lawn. On examination he had hands motion only vision.
There was a 7-clock-hour iridodialysis and vitreous was filling the anterior
chamber. A ruptured, white lens was enmeshed in vitreous at the inferonasal
vitreous base. Commotio retinae was present.
First, the loose iris leaflet was captured by two flexible iris retractors (Grieshaber). A pars plana lensectomy, vitrectomy, and scleral buckle procedure were performed. The iridodialysis was repaired, yielding a 9-mm mydriatic pupil despite intraocular acetylcholine. A posterior chamber IOL was sutured to the scleral wall and the pupil margin was imbricated (Slide 8).
Case 4: Multiple Sphincterotomies
At the time of a 60-year-old woman’s cataract surgery,
the surgeon considered the pupil too small. Therefore, multiple
sphincterotomies were created, causing a permanent widely dilated pupil. She
complained of glare and was dissatisfied with her cosmetic appearance. After
seeking several unpromising opinions elsewhere, she came to the office for
consultation.
On examination, she had a widely dilated resting pupil with the IOL edge exposed for 180°. Seven sphincterotomies were present, two of which traversed the sphincter muscle entirely.
The patient chose to undergo elective repair. Each sphincterotomy was closed with the closed-chamber, sliding knot suture technique, achieving elimination of glare with an excellent functional and cosmetic result (Slide 9).
When a significant amount of iris tissue is damaged or
missing, iris repair may not be possible. In these cases, 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 approved by the U.S. Food and Drug
Administration. The currently manufactured iris implants are available in five
categories: large diameter, rigid iris diaphragms with or without a central
optic (Ophtec BV, The Netherlands, and Morcher GMBH, Germany) (Slide 10 and Slide 11);
overlapping, interdigitating iris rings (Morcher) (Slide
12);
capsular tension rings with opaque iris segments (Morcher) (Slide 13); intracapsular Hermeking iris prosthetic
system implants (Ophtec) (Slide 14A and
Slide 14B); and custom iris implants with enclavation fixation (Ophtec) (Slide 15).
The products from Morcher are manufactured with black PMMA. Careful handling reduces haptic breakage since black PMMA is more brittle than standard PMMA. Ophtec’s products are made of Perspex in blue, green, and brown colors (Slide 16).
The currently manufactured products can significantly reduce patients’ glare and photophobia. The appropriate implant choice is often highly specific to a patient’s anterior segment anatomy.
The optimal outer and inner diameters of iris implants and the optimal design, material, and relation to an implanted optic have yet to be definitively determined. I am hopeful that continued evolutions in design and an increasingly facile, less costly FDA approval process will spur both iris implant development and availability. I anticipate that further study and innovation will provide implants that are increasingly effective and, perhaps, may simultaneously address iris cosmesis.
With meticulous surgical technique, most patients with an abnormal pupil can benefit both functionally and psychosocially from iris reconstruction. For patients whose native iris is damaged beyond reasonable repair, artificial iris implants and segments provide an excellent option.