Iris Defects and Complications

32   Iris Defects and Complications


Kenneth J. Rosenthal


Iris defects in the context of cataract surgery may either be preexisting or occur iatrogenically during the surgical procedure. The careful and appropriate assessment and treatment of these conditions will directly impact the success of the procedure and, indeed, make the completion of the procedure possible. Failure to address iris complications or comorbidities at the time of surgery, or in a planned sequence of surgical procedure, will cause an otherwise successful cataract extraction to fail and the patient to be dissatisfied.


Patients with iris defects present surgical challenges because the anterior segment may destabilize after cataract removal and because the implantation of a traditional intraocular lens (IOL) may result in the patient experiencing significant glare, photophobia, and polyopsia.


Furthermore, with some iris defects, such as those associated with iridocorneal endothelial syndrome, or in eyes with other comorbid conditions, such as retinal abnormalities or glaucoma, the overall success of the procedure may ultimately be compromised by the progression of the disease. These defects should be carefully assessed in determining the surgical strategy and prognosis for the patient.


It is equally important to diagnose the iris defect accurately, as its treatment will differ widely depending on its extent and on its cause. Iris repair can be accomplished by a variety of techniques and utilizing a variety of devices. In general, the repair is performed by cerclage, direct or indirect iris suture, or implantation of a prosthetic iris. Additionally, contact lenses and corneal tattooing, although infrequently performed, can be used to block unwanted excess light.


Patient Assessment


In the patient with preexisting iris defects, it is important to take a careful history. One must understand how the defect occurred, what previous treatments have been tried, and what options exist for ameliorating or repairing the condition. Of ultimate importance, however, is carefully querying the patient as to the extent of visual disability. Although larger iris defects generally have more symptoms, there are important exceptions to this paradigm, and consideration should be given to not repairing or replacing the iris tissue in patients who do not have significant symptoms.


Symptoms


Patients with iris defects may have little or no visual compromise, or may have symptoms that are so severe as to be debilitating. The most common symptoms are the following:



  1. Photophobia: The aversion to light is generally extreme, so that even normal indoor lighting may be troublesome. Patients with large iris defects are almost completely unable to tolerate outdoor sunlight without wearing dark sunglasses for protection.
  2. Glare: Patients may experience starbursts, halos, or hazy vision, particularly in bright light, but even in poor lighting.
  3. Decreased visual quality: Patients experience poor contrast sensitivity. This is most likely related to the transmission to the retina of higher order aberrations (particularly spherical aberration), due to light traveling through the peripheral cornea, which is unguarded by the peripheral iris. This latter is particularly important in assessing patients with congenital aniridia (discussed below). These patients frequently also suffer from foveolar hypoplasia, and accordingly their best visual potential is ∼ 20/100 or less. However, despite the fact that their Snellen acuity may not significantly improve after iris prosthetic implant surgery, these patients universally note a dramatic improvement in their functional vision.
  4. Cosmetic defects: Patients with iris defects may suffer from poor self-esteem, self-consciousness, and depression due to their iris color and iris configuration. Additionally, because the eyes are often the first characteristic others notice about an individual, the presence of obvious iris abnormalities may affect how patients are perceived and reacted to by others. Cosmetic improvement, particularly at the time of cataract surgery, can be helpful in improving the emotional disposition of patients suffering from externally visible iris defects, and thus the clinician should ask patients how they feel about themselves.

Function of the Iris


To appropriately repair iris defects, a clear understanding of the iris/pupil function is crucial. In addition to the obvious function of modulating light entrance through the pupil the iris has other equally important functions, particularly in the context of cataract surgery. So the repair should be designed to obliterate the pseudophakic/aphakic junction in patients with IOL implants. Other goals of treatment are as follows



  1. Reduce confusional focused/unfocused images
  2. Reduce peripheral asphericity and optical aberrations
  3. Decrease pupil size, therefore reducing photophobia
  4. Improve cosmesis

The absent or fully dilated pupil may be of a diameter in excess of 10 mm, whereas the largest IOL available in the United States is 6.5 mm in diameter (and most IOLs are 6 mm or less). Accordingly, under these circumstances, light entering the eye presents a focused image (through the IOL) along with a superimposed defocused image (around the edge of the IOL—aphakic). Similarly, patients with multiple iris defects may suffer from polyopsia, ghosting, poor contrast sensitivity, or reduction in visual quality. These phenomena negatively impact the patients’ vision. Reducing peripheral asphericity and optical aberrations caused by light entering the peripheral cornea may reduce contrast sensitivity. Finally, the presence of iris defects, especially in light-colored eyes, may impart a significant cosmetic defect; patients may present with this defect as the sole complaint, and the risks, benefits, and advisability of repair in the absence of significant visual compromise should be given due consideration. Improvement in cosmetic appearance can be accomplished by iris repair or implantation of an iris prosthetic device.


Classification and Strategies for Repair of Iris Defects


Iris abnormalities may be assessed by their etiologies, their physical configuration, and their physiological/ophthalmic impact upon the patient.


Traumatic Etiologies


Diseases that cause iris abnormalities are summarized in Box 32.1. Generally, they can be divided into developmental and traumatic anomalies. The trauma can be blunt or penetrating. In such cases, the surgeon should be aware of the likely concomitance of zonular dehiscence (particularly in blunt trauma), and of lens perforation (in penetrating trauma), as well as of corneal injury. In fact, in blunt trauma with iris defects, the surgeon should be prepared to address vitreous prolapse and repair of zonular defects with capsular tension rings as they almost always occur together.


Iatrogenic conditions include surgical trauma, idiopathic postoperative mydriasis, and mydriasis related to prolonged increased intraocular pressure (IOP), both in the postoperative period and as a sequela to untreated angle closure glaucoma, as a result of IOP-related iris sphincter damage. Intraoperative snagging of the iris with instruments and devices may cause iridodialysis (Figs. 32.1 and 32.2).



And the preoperative use of systemic α1-antagonists such as tamsulosin (Flomax), doxazosin (Cardura), silodosin (Rapaflo), prazosin (Minipress), alfuzosin (Uroxatral), and terazosin used in the treatment of both hypertension andbenign prostatic hypertrophy-related urinary frequency—may lead to intraoperative floppy iris syndrome (IFIS), resulting in transillumination defects, iris prolapse, and chronic mydriasis (Fig. 32.3). The intraoperative/preoperative management of this condition is discussed in Chapter 23. Iatrogenic traumatic aniridia has been reported in conjunction with endoscopic cyclophotocoagulation.1


Congenital and Developmental Etiologies


Congenital and developmental iris defects occur in a variety of conditions, including congenital aniridia, coloboma, iridocorneal endothelial syndrome, Axenfeld-Rieger syndrome, uveitis, and idiopathic postoperative mydriasis. Many patients have coexisting zonular and capsular abnormalities. In congenital aniridia, for example, the capsule may be thinned and lack elasticity, described by Robert Osher as being comparable to “wet toilet tissue.” The surgeon should be prepared for this condition, and should modify the surgical technique to perform a well-controlled capsulotomy in these cases. In congenital aniridia in children, as in all pediatric cataracts, the capsule is universally rubbery, and a controlled rhexis can be challenging as well. Use of hyperviscous viscoelastics (e.g., Healon-5, Abbott Medical Optics, Abbott Park, IL) can aid in tamponading the capsule in both of these aniridic scenarios.



Box 32.1 Causes of Iris Defects


Developmental



  • Coloboma
  • Iridocorneal endothelial syndrome
  • Axenfeld-Rieger syndrome
  • Congenital aniridia
  • Ectropion uveae
  • Albinism (transillumination)

Traumatic



  • Surgical

    • Intraoperative floppy iris syndrome
    • Iridodialysis from instrumentation
    • Chronic elevation of intraocular pressure

  • Nonsurgical

    • Percussive trauma
    • Penetrating trauma



Classification of Iris Defects by Physical Types and Treatment Approach

Total or Subtotal Aniridia/Functional Aniridia

Complete functional absence of the iris occurs in patients with congenital aniridia and trauma, both surgical and penetrating. As a surgical complication, complete iridodialysis may rarely occur. Congenital and acquired ectropion uveae may also present as functional partial or full aniridia. Percussive injury may also cause complete iridodialysis. Congenital aniridia should more accurately be called “hypoplastic iris syndrome,” because almost all of these patients have an iris root present, although it serves no function. Infrequently, these hypoplastic remnants can be surgically stretched toward the center of the pupil and sutured, using a cerclage or quadrantic approach (see below). However, the vast majority of such cases, both congenital and acquired, have inadequate iris tissue to provide optically useful closure, and thus care must be taken not to overstretch the iris remnants, which could cause iridodialysis or iris root hemorrhage. Most patients with these abnormalities are likely to benefit from an iris prosthetic implant. When possible, the implant should be placed at the time of primary surgery or at the time of definitive reconstruction of trauma cases. These surgical steps can be performed sequentially. For example, in the United States it is common to perform iris implantation on a patient who has already had otherwise routine cataract surgery, because of the paucity of available devices at the time of the initial surgery. My experience is that this does not significantly impact the success of the procedure, however.


Transillumination Defects

Transillumination defects (TIDs) are not obvious in all cases. The examiner should be alerted to their possible presence by the patient’s history. There is almost always diffuse transillumination in patients with ocular albinism, and the placement of an iris implant to mask this transillumination will markedly decrease photophobia and increase patients’ visual potential.2


Transillumination defects may also occur in patients with IFIS or intraoperative iris prolapse, due to stretching of the iris tissue. TIDs have also been reported after blunt trauma, after vitrectomy, and after implantation of IOLs, usually single-piece IOLs in the sulcus,3 or sutured to the posterior iris. We reported a case of TIDs related to in-the-bag implantation of a single piece acrylate IOL in conjunction with trabeculectomy using an EX-PRESS Glaucoma Filtration Device (Alcon Laboratories, Inc., Fort Worth, TX)4 (Fig. 32.4).



Many TIDs are asymptomatic, particularly those covered by the upper eyelid, and they do not require treatment. However, they can be the source of poor visual quality and photophobia, especially when located within the palpebral fissure, and especially when located temporally (a common location for TIDs caused by iris prolapse). In such cases, the treatment is proportional to the extent of the defect. Smaller, well-circumscribed TIDs can be treated with a plication suture, whereas larger ones may require an iris prosthetic implant.


Polycoria

The presence of multiple pseudopupillary openings in the iris creates a “moth-eaten” appearance. This may occur in acquired disorders such as Axenfeld-Rieger syndrome or anterior embryotoxon. The first case of modular/small incision iris implantation, which I reported in 1996, was in a patient wit Axenfeld-Rieger syndrome. This problem exists more commonly due to surgical and penetrating trauma, however, particularly with IFIS (Fig. 32.5). As with TIDs, the extent and location of the localized iris defect determines its treatment. Smaller areas can be treated effectively with an imbrication suture, whereas larger ones require iris implantation.


Sector Defects: Coloboma

True iris coloboma is a congenital disorder of the iris arising from failure of the embryonic optic plate to fully fuse when forming the embryonic fissure in the fifth week of gestation, resulting in a “keyhole-shaped” pupil. An iris coloboma can be associated with colobomas of the ciliary body, choroid, retina, or optic nerve. Iris colobomas are typically located in the infer-onasal quadrant. They frequently affect the entire uveal tract, which therefore may include the iris, ciliary body (including the zonule), optic nerve retina, and choroid. When present only anteriorly, it creates only an iris defect with attendant photophobia and decrease visual quality. Patients with this deformity are frequently very self-conscious about their appearance, and often present for cosmetic improvement even in the absence of symptoms.


In treating such conditions as part of a cataract extraction, it is crucial to keep in mind that these patients are almost always lacking zonules in the area peripheral to the iris defect, and appropriate measures include capsular support with hooks or capsular tension ring, and placement of retentive viscoelastic overlying the area of defect, so as to prevent vitreous prolapse. This topic is discussed further in Chapters 25 and 26.


Closure of the colobomatous defect can be accomplished by the use of a Siepser knot,5 or one of its variants,6 if there is adequate tissue to allow it. No undue amount of tension should be placed on the iris or on the suture, as this may cause bleeding or iridodialysis; however, the iris is sufficiently elastic to allow primary closure. In iris colobomas that extend two or more clock hour positions, however, it is prudent to consider the placement of an iris prosthetic implant. This can be accomplished by using a rigid “sector” iris implant or a flexible implant in which the superior, noncolobomatous area is cut out to provide access through the superior pupil when dilated (for dilation exam and low lighting conditions) (Fig. 32.6).




Atonic Pupil

Chronic mydriasis is generally caused by the failure of the iris sphincter, mechanical damage to the myofibrils, or stretching of the iris stroma. Common etiologies are blunt trauma (traumatic mydriasis), prolonged elevation of IOP as in acute angle closure glaucoma, in prolonged postoperative pressure spike, and inflammation. Idiopathic instances also have been known to occur.


The treatment of this condition overlaps with the strategy for congenital aniridia; however, it is much more likely that some degree of pupillary closure can be accomplished by cerclage or by quadrantic iris suture, described below. For large or chronic mydriasis, and particularly in patients with light-colored irises, where the iris stromal pigment is scant to begin with, closure, even when it can be performed, may result in inadequate pupillary closure or diffuse and visually significant TIDS. In these patients, as in all patients with inadequate iris stroma in general, an iris prosthetic device is the preferred strategy. In patients in whom there are obstacles to obtaining the iris prosthesis, or in borderline cases, due consideration should be given to a stepwise approach: repair, and then, if it fails, implantation of iris prosthesis. The patient should be aware of the relative risks and benefits of each of these approaches, particularly a patient who may be at risk for poor healing after multiple surgeries, such as a patient with poor corneal endothelial function, immune compromise, or diabetes.


Iridodialysis

Iridodialysis, in which the iris root is disinserted from the sclera, occurs most commonly due to trauma, although it may rarely occur secondary to degenerative disease. Surgically induced iridodialysis is commonly seen in conjunction with iris prolapse or with the inadvertent tethering of the iris with an instrument (Fig. 32.7). In such cases, prompt repair of these conditions may result in a good restoration of function.


Posterior Synechiae and Chronic Miosis

Synechiae that cause adhesion of the iris to the anterior lens capsule can present with challenges to completion of surgery. They can be addressed by viscoelevation of the normal adjacent iris combined with the use of a cyclodialysis spatula to lyse the adhesion, or by the use of a microforceps to remove a fine pupillary membrane.


Stretching of the pupil with various instruments can also be performed, but should be avoided in cases of IFIS. These techniques are covered more in detail elsewhere in this book, but it is important to keep in mind that, particularly in cases of IFIS, overzealous stretching or lysis of the pupillary ruff may result in chronic mydriasis that requires sequential surgical intervention.


Visually Detracting Iridectomies and Iridotomies

The iridectomy/iridotomy is the most commonly used surgical strategy for creation of a confluence between the posterior and anterior chambers, particularly in narrow-angle disease. Although this procedure generally is well tolerated, some patients may be sensitive to the stray light entrance through these openings, particularly when there are large areas open. These problems may be alleviated by partial closure of the iridotomy or by corneal tattooing overlying the iris defect.


May 13, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Iris Defects and Complications
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