13.2.1 Contact Lens

The artificial iris is incredibly useful in patients because it can be effective even when there is no residual native iris tissue. However, sometimes we can use a nonsurgical or alternative surgical approaches to these iris abnormalities. One solution is the use of an opaque periphery contact lens that acts to block out the incoming light with an outer diaphragm, coined “aniridic contacts.” (▶Fig. 13.1) In many cases, however, patients report so much discomfort from the lenses due to the thickness and lesser oxygen transmission of these contacts that they would rather deal with their previous symptoms than wear them. Additionally, these lenses are not ideal in patients with coexisting corneal abnormalities, many times, presenting hand in hand with iris defects. The incoming light is blocked more anteriorly relative to the nodal point of the eye in these cases, at the corneal plane, which can still cause persisting photic symptoms in pseudophakic patients and can induce a visual field limitation in other patients.

13.2.2 Corneal Tattoos

In other cases, corneal tattoos have been performed on select patients. The femtosecond laser has even been used to help create a pocket for the pigmentation. However, this treatment is not reversible and may inhibit examination of the other parts of the eye, particularly the fundus. Studies have reported successful treatments of patients with minimal adverse effects. However, Alio et al, in a more recent study, reviewed 234 eyes that underwent treatment, and up to 49% of those patients experienced some level of light sensitivity. Others experienced visual field defects and difficulty with magnetic resonance imaging. The learning curve is steep for this procedure and severe complications can result. ^{3 , 4 , 5 , 6}

13.2.3 Direct Suturing

When there is enough residual iris tissue to adequately resolve the defect, a suture iridoplasty may be helpful. In patients with a localized iris defect of minimal clock hours or sectors, either a Siepser knot or one of its variants ^{7 , 8} can be used. For more peripheral defects, a direct closure with a McCannel suture can be employed. ⁹ In cases of large pupillary dilation, an iris cerclage technique can be performed to decrease the size of the pupil. However, in lighter irides or subtle translucencies, the patient can still experience photic discomfort even if the pupil appears cosmetically improved. ¹⁰ Other patients with symptomatic iridodialysis can be repaired by utilizing a 9–0 or 10–0 prolene suture on a double-armed needle and suturing it to the scleral wall. However, many times, this can distort the pupil, even if a hang back technique is used to help prevent this distortion. While all the above techniques can be employed in the right patients, many times, an artificial iris prosthesis accomplishes many of the goals of repair that most of the other alternatives lack.

13.3.1 Complete or Near-Complete Iris Deficiency

This type of deficit can be broken down into congenital, acquired, or traumatic causes. Congenital aniridia is a panophthalmic disorder that’s most notable feature is a hypoplastic iris. The severity of hypoplasia ranges from total absence (at least rudimentary stump is present in all cases) to only a mild deficit of iris tissue. The condition is either spontaneous or familial in the form of an autosomal dominant inheritance of a defect in the PAX6 gene on band 11p13. The familial condition has complete penetrance but variable expressivity. The sporadic form is associated with Wilms tumor, aniridia, genitourinary anomalies, and mental retardation syndrome, specifically Wilms tumor. As discussed previously, many iris defects are associated with concomitant ocular conditions. In the case of congenital aniridia, the effects can range from isolated iris deficiency to abnormalities of the lens, optic nerve, fovea, and cornea; just to name a few. The mild iris hypoplasia variant could be confused with Axenfeld–Rieger syndrome; therefore, careful examination of these patients is the most prudent way to prepare for possible challenges during surgery. ^{11 , 12}

Performing surgery on aniridia patients can be quite challenging due to inherent zonular instability and thin capsules. ¹³ Additionally, a small percentage of these patients can experience a phenomenon called aniridia fibrosis syndrome that can be devastating and sight-threatening. This progressive fibrosis can occur in around 5% of patients with aniridia with no particular preference towards the type of intraocular surgery as the inciting factor. ^{14 , 15} Though no exact cause is known at this time and no specific type of surgery is known to cause the progression, we recommend placement of the artificial iris within the capsular bag, when possible, versus the sulcus. If possible, this could be performed at the time of cataract surgery, obviating a sulcus device and potential irritation of the residual native iris tissue and/or the ciliary body.

Although it is somewhat uncommon to see a complete or near-complete iris deficiency from trauma, a large iridodialysis from blunt trauma can cause functional aniridia. Contusion or penetrating injuries in rare cases could be severe enough to leave a patient functionally aniridic as well. Even iatrogenic injuries during cataract surgery in a patient with intraoperative floppy iris syndrome (IFIS) or from a complication from insertion or removal of an intraocular device could potentially leave a patient with a large defect. These patients should be carefully managed for coexisting medical and surgical problems caused by the trauma itself.

13.3.2 Partial Iris Deficiency

This category encompasses a large variety of potential iris defects that, like the previous category, can be broken into congenital/acquired versus traumatic/iatrogenic causes. Axenfeld–Rieger syndrome is one of the most common causes of stromal hypoplasia. It is inherited in an autosomal dominant fashion by mutations in the PITX2 gene on band 4q25. The iris anomalies can vary from mild transillumination defects to such severe hypoplasia that can be confused with congenital aniridia. Notably, these patients experience polycoria that renders functional vision almost entirely impossible. In many cases, there will not be enough iris tissue to repair directly; therefore, an iris prosthesis would be more effective. The importance of concomitant disease is again stressed because up to 50% of these patients can have glaucoma that should be coordinated with their glaucoma provider should you choose to take on the task.

Patients with more sectoral defects like in iris coloboma, typically located in the inferonasal quadrant and associated with posterior uveal colobomas, might be able to be repaired without a prosthesis utilizing a suture iridoplasty approach if small and enough iris tissue is present. Individual analysis of the iris parameters can help predict whether this approach will be successful. ¹¹ Other partial iris deficiencies like iridocorneal endothelial (ICE) syndrome are characterized by epithelial-like metaplasia and abnormal proliferation of the corneal endothelium, resulting in the spread of the “ICE” cells to other parts of the anterior segment, including the iris. ^{16 , 17} These membranes can cause an iris that would not stretch with the previously described suturing techniques; therefore, likely an iris prosthesis is the best choice in these patients.

Iatrogenic iris damage from IFIS can occur during cataract surgery, which can vary in severity. Additionally, penetrating trauma can result in varying iris deficiencies. In some cases, a tumor excision will leave a small enough sectoral defect that can be repaired directly, but this is heterogeneous as well.

13.3.3 Pigment Deficiency

These particular patients can range from congenital absence of melanin like in ocular albinism to conditions acquired from surgical complications, intraocular infections, or chronic inflammation. Ocular albinism has an X-linked inheritance and results in patients with normal iris anatomy but a lack of melanin in the posterior pigment epithelial layer. These patients can experience severe photoaversion that tends to be the main complaint. Normally, incident light exits only through the pupil, but in these patients, the light penetrates directly through the iris. It can be made even worse by implantation of an IOL as the light penetrates and reflects directly off the haptics. ¹⁸

This similar lack of pigment can also be found in systemic diseases like Chediak–Higashi syndrome and Hermansky–Pudlak syndrome, both of which have serious associated systemic health issues. IFIS also leads to a surgical cause of pigment deficiency without full-thickness defects that can be symptomatic in some patients. Many of these types of syndromes and causes would be excellent candidates for an iris prosthesis.

13.3.4 Constriction Deficiency

Most of these types of patients are a result of trauma, increased intraocular pressure (IOP), Adie’s tonic pupil, or inflammatory disease. As discussed earlier in the chapter, an iris cerclage might be an adequate option in some cases, but light transmission could still be an issue. A discussion with the patient about the possible options, risks, and benefits might yield an iris prosthesis as the most satisfying solution.

13.5.1 Iris–Lens Diaphragm Models

Ever since the first implantation of this type of model by Sundmacher, there have been a few updated designs over the years. The major advantage of this type of design is that it solves a problem of aniridia and aphakia all in one device and surgery. As we reviewed earlier, of the currently available designs, this model type has been around the longest compared to the other designs. Its long history lends us years of experience with its advantages and disadvantages. ^{25 , 26 , 27} The design has reasonable outcomes despite some disadvantages. First, the material of PMMA is rigid and the models are large, requiring an incision up to 10 mm to implant the device safely without breakage. Because the current models only come in a few select colors (mostly black), these can appear unnatural to patients and aesthetically artificial. Additionally, in the smaller optic models, some patients can experience dysphotopsias.

Two companies currently distribute this type of model, Ophtec BV and Morcher, with updates and variations. Ideally, these models are implanted into the capsular bag. However, since that can prove difficult in many cases, they can also be implanted into the sulcus passively or with scleral fixation. Morcher offers variable designs based on the patient’s needs, all available in the color black. Some of the models come in smaller sizes that are asymmetric for the use in patients with only sectoral loss. This reduces the need for a larger incision for implantation. The optics range in size from 3 to 6.5 mm and from 10 to 30 D, and the overall diameter of the models ranges from 12.5 to 13.75 mm. The pseudopupillary apertures range in size as well. The process that is used to make the black PMMA opaque results in a more brittle material that can be prone to breakage during maneuvering.

The Ophtec 311 models give the advantage of a few different color choices (light blue, light green, or brown). The pseudopupil diameter is 4 mm and the overall diameter is 13.75 mm. The optic comes in a range of 1 to 30 D in 0.5-D increments as well as a plano lens. This material reflects ambient light and can appear unnatural compared to the fellow eye. However, the haptics are a bit more resistant to flex; therefore, breakage is less common than the Morcher models. Like the Morcher model, the overall large diameter makes placement in the capsular bag more difficult due to the possibility of capsular tear or zonular stress. The optic has a rounded edge to help reduce glare and is inset with a bevel into the iris complex. Both Morcher and Ophtec offer designs with or without optics. Ophtec also offers an Artisan iris-fixated lens with an optic as well. However, these types of lenses require enough iris tissue to safely fixate the lens; therefore, they are used less often.

Reper, a relative newcomer to space, is a Russian firm, which manufactures a similar combined IOL–iris diaphragm device made from hydrophobic acrylic with a variety of colors of embedded pigment. The Russian unit comes in a number of geometries for different anatomic placement or configuration. This device has been used sporadically internationally and recently received CE mark in Europe. As of yet, to the best of our knowledge, there is no US experience with this product. ²⁸