|Year : 2021 | Volume
| Issue : 2 | Page : 69-73
Iris reconstruction: A perspective on the modern surgical armamentarium
Alexandra Crawford1, Simone Freundlich2, Jie Zhang2, Charles Ninian John McGhee1
1 Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland; Department of Ophthalmology, Greenlane Clinical Centre, Auckland District Health Board, Auckland, New Zealand
2 Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
|Date of Submission||20-May-2021|
|Date of Acceptance||21-May-2021|
|Date of Web Publication||28-Jun-2021|
Prof. Charles Ninian John McGhee
Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, Private Bag 92019, University of Auckland, Auckland
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The surgical reconstruction of eyes with iris defects is almost invariably complex and challenging. A number of prosthetic iris devices are available including large-incision, rigid diaphragm, aniridic intraocular lens style devices, small-incision devices incorporating a capsular ring, and flexible, customized, small-incision iris prostheses. The surgical techniques for rehabilitation are dictated by the configuration of the iris defect, the presence of concurrent ocular pathology, and the functional complaint of the patient. Successful rehabilitation requires careful surgical planning and appropriate patient selection. Nonetheless, endowed with the modern surgical armamentarium, the reconstructive surgeon may achieve significant functional and cosmetic improvement.
Keywords: Artificial iris, iris reconstruction, pupilloplasty
|How to cite this article:|
Crawford A, Freundlich S, Zhang J, John McGhee CN. Iris reconstruction: A perspective on the modern surgical armamentarium. Oman J Ophthalmol 2021;14:69-73
|How to cite this URL:|
Crawford A, Freundlich S, Zhang J, John McGhee CN. Iris reconstruction: A perspective on the modern surgical armamentarium. Oman J Ophthalmol [serial online] 2021 [cited 2021 Sep 18];14:69-73. Available from: https://www.ojoonline.org/text.asp?2021/14/2/69/319480
| Introduction|| |
Defects of the iris may have significant functional and aesthetic implications. Of all facial features, the appearance of an individual's eyes has the greatest influence on how we perceive and interpret human faces. The human gaze centers on the eyes for information processing during facial recognition, and the eyes have an important role in conveying social cues such as the direction of gaze and emotion. Humans are attuned to subtle alterations in eye appearance, and perceived defects may result in social stigma and an adverse psychological impact. Indeed, patients with iris defects self-report considerable cosmetic disturbance.
The iris has key optical functions: It modulates light thereby reducing glare and photophobia and plays an important role in visual quality by accommodative miosis. Furthermore, variations in pupil diameter influence both contrast sensitivity, and the amount and character of higher-order aberrations. Visual disturbances associated with iris defects include photophobia, glare, haloes, difficulty reading, altered contrast sensitivity, poor visual quality, diplopia, and light/dark disorder.
The causes of iris defects can be broadly categorized into congenital, acquired, or traumatic causes. The type of iris defect can broadly be categorized as: (a) complete, near-complete or partial physical deficiency, (b) pigment deficiency, (c) dilation or constriction deficiency. Management options for iris defects are guided by the type of iris defect, and the presence of other ocular comorbidities. These include tinted spectacles, aniridic contact lenses, focal corneal tattoos, direct suturing/pupilloplasty, partial aniridia segment rings with or without pupilloplasty or a full artificial iris implant.
| The Modern Surgical Armamentarium|| |
The concept of minimally invasive pupilloplasty was first introduced by McCannel in 1976 [Figure 1]a and [Figure 1]b. In his original technique, the iris defect was approximated within the confines of the anterior chamber by passing a long needle via two corneal paracentesis incisions. The technique was subsequently modified to a sliding knot technique by Siepser in 1994. A more recent incarnation of the pupilloplasty procedure is a single-pass four-throw technique, wherein only one pass is made into the anterior chamber. Pupilloplasty works best when the iris defect is small (<90°), and the remnant iris tissue is of sufficient quality and quantity to achieve a functional pupillary aperture.
|Figure 1: (a) a case of severe traumatic mydriasis in floppy iris syndrome treated by five prolene sutures using a McCannell type approach to reduce pupil size from 8 mm to around 4 mm. (b) Single suture inferior pupilloplasty combined with a black capsular tension ring iris segment (with overlying capsular fibrosis) in an eye with an iris defect following excision of an iris tumour|
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While technically challenging, pupilloplasty can be effective in reapproximating the pupil shape and reducing the size of the iris defect, and therefore should be the first option considered in iris repair. Limitations of pupilloplasty include: exacerbation of the iris damage through intraoperative manipulation, excessive tension causing tear-through of sutures, poor approximation, insufficient reduction in pupil size, and unsatisfactory cosmesis.
Prosthetic iris devices
A number of prosthetic iris devices are available including large-incision, rigid diaphragm, aniridic intraocular lens (IOL) style devices, small-incision devices incorporating a capsular ring, and flexible, customized, small-incision iris prostheses. Each device has its own niche and device selection is influenced by the ocular anatomy, functional requirements of the patient and cost. Some devices are designed for placement within the capsular bag, whereas others are intended for either passive or suture fixation in the ciliary sulcus.
Rigid large-incision intraocular lens style devices
Rigid diaphragm devices have a peripheral opaque annulus with IOL-style haptics that functions as an artificial iris. The devices can be manufactured either with an affixed central lens optic (aniridic IOL) or with an open aperture. These rigid prostheses require a large (approximately 10.5 mm limbal/corneal) incision and are typically trans-scleral, suture-fixated in the ciliary sulcus, though passive placement in the sulcus is possible in the context of adequate capsular support.
The Morcher GMBH 67 series of aniridia implants with IOL uses a black polyethyl methacrylate (PEMA) for the peripheral opaque zone and clear polymethyl methacrylate for the clear central optic [Figure 2]. The rigid C-shaped haptics have eyelets to facilitate suture fixation. As the peripheral border is black, the device does not offer any cosmetic advantage but reduces the overall pupil diameter. With time the overlying lens capsule undergoes fibrosis and the grey appearance may improve cosmesis in blue and light colored irides. A number of different effective pupil apertures are available ranging in size from 3.5 mm to 6.5 mm.
|Figure 2: A scleral sutured Type 67G Morcher aniridia implant with intraocular lens in an eye that was rendered aniridic and aphakic following globe rupture in a road traffic accident. The rigid intraocular lens and iris prosthesis requires a large limbal incision|
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Ophtec BV manufactures a rigid prosthetic device (HMK ANI 2 Model 311) made of Perspex with impregnated pigment. The device is available with or without an optic and comes in three standard colors; brown, green, and blue. As the colors are standardized rather than customized, the cosmetic outcome is variable and may appear artificial and draw more attention to the iris repair depending on the subject's iris color.
Small-incision devices incorporating a capsular ring
In eyes undergoing cataract surgery with an intact capsulorhexis and good capsular support, iris defect repair can be achieved through the insertion of an endocapsular, small-incision, iris segment. Morcher manufactures several endocapsular, tension ring-based, models which can be inserted through a minimum 3.5 mm wound. These devices consist of a capsular tension ring (CTR) backbone with many different iterations of black PEMA fin segments. Two different types are available: the Type 50 aniridia rings for complete reconstruction [Figure 3]a and [Figure 3]b and the 96 Series partial aniridia rings for treatment of segmental loss [Figure 3c and d]. These devices are available in a range of sizes to provide different effective pupil diameters. The aniridia rings are available in three different effective pupil sizes: 3.5 mm (Type 50E), 4.0 mm (Type 50F), and 6.0 mm (Type 96C). The Type 96F and 96G partial rings have an effective pupil diameter of 4 mm, whereas the Type 96E and 94G provide a 5.5- and 6.5-mm diameter, respectively.
|Figure 3: (a) Intraoperative image showing one Type 50.F Morcher capsular tension ring within the capsular bag in front of the intraocular lens and the second device immediately before insertion in a case of longstanding, severe traumatic mydriasis. (b) The second identical endocapsular ring is dialed in front of the first ring within the capsular bag. The fins of the two devices overlap creating a completely opaque peripheral zone and a small artificial pupil at the end of the procedure (note minimal contraction of the natural pupil despite intracameral acetylcholine). (c) Image showing (in a pharmacologically dilated pupil) two overlapping, temporal sited, Type 96F Morcher segments plus an intraocular lens in the capsular bag, in an eye with an area of asymmetric traumatic mydriasis following previous trauma. (d) Image of the same eye demonstrating functional pupillary aperture in the resting ambient state of iris constriction|
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The Morcher 50 Series consists of eight occluder panels/fins on a CTR backbone. Two overlapping Morcher 50 Series devices can be used, such that interdigitation of the segments, enables complete 360° peripheral coverage if required.
The Morcher segmental 96 Series device consists of a single fin segment and is suitable for sectorial defects that extend between 90° and 180°. In larger iris defects, overlapping segment fins can be positioned side by side to accommodate a defect of up to 180°. An adjunctive pupilloplasty should always be considered to reduce the iris defect where possible to achieve the greatest coverage with the iris segment.
Placement of the iris segment in the capsular bag avoids contact with the ciliary body and angle structures, minimizing postoperative inflammation and reducing the risk of uveitis-glaucoma-hyphaema syndrome. Disadvantages include susceptibility to fracture if over-manipulated, no cosmetic advantage, surgical complexity particularly with the 50 Series inserted with an IOL, and the need for an intact capsular bag.
Customised flexible small-incision iris prostheses
The HumanOptics CustomFlex® Artificial Iris is a flexible small-incision iris prosthesis and is currently the only US food and drug administration approved intraocular prosthesis [Figure 4]. It is composed of a flexible biocompatible silicone elastomer and is provided with a diameter of approximately 12.8 mm with a fixed pupil aperture of 3.35 mm. The profile is 0.4 mm in the center tapering to 0.25 mm in the periphery to minimize the formation of synechiae. The iris may be ordered either with or without internal fiber, with the former developed to create greater structural integrity of the prosthesis for cases where suture fixation is required.
|Figure 4: Intraoperative video image of insertion and unfurling of a HumanOptics CustomFlex® artificial iris (10 mm diameter) through a temporal corneal incision into the capsular bag in front of the intraocular lens, in a case with almost six clock hours of iris deficit (from approximately 1–7 clock hours) following wide-iridectomy treatment of a pigmented iris lesion|
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The flexible silicone material of the artificial iris permits a small incision size; only 2.5–2.8 mm for the fiber-free option and 3.2 mm for the model with fiber (though larger corneoscleral incisions may be required and may be beneficial in more complex cases). Importantly, this iris prosthesis can be adapted to the specific conditions of the affected eye: (a) a corneal trephine may be used to cut the prosthesis to the desired diameter; (b) it can be inserted via an IOL injector or simply folded for insertion; (c) it can be inserted into the capsular bag accompanied by an intraocular len; (d) it may be inserted into the ciliary sulcus, without suturing, where there is adequate IOL-capsular support; (e) scleral-suture-fixation is possible, with or without a suture fixated IOL, where there is no capsular support.
The silicone prosthetic iris is customized for each patient based on a photograph of the healthy iris of the fellow eye. In individuals with congenital bilateral iris defects, a photograph of the desired eye color is used, e.g. from a parent or sibling. In order to minimize deviations in iris hue from the contralateral eye reference color, high quality, printed, photographs taken in natural light are preferred to digital files, and these prints can be verified and signed by the patient and surgeon before ordering.
The iris is hand-crafted by the manufacturer using pigmented silicone. The anterior surface of the iris has a subtle undulating contour which minimizes light reflection and improves the natural aesthetic appearance. It cannot be over-emphasized that this iris prosthesis is not intended for cosmetic change in eye color and should only be placed in the eyes following removal of the crystalline lens.
Unfortunately, different cosmetic iris prosthesis models are marketed for patients who wish to alter their natural eye color in an otherwise normal eye. Importantly, these purely cosmetic implants are associated with significant and often irreversible, potentially blinding, complications,, and their use is strongly discouraged by the authors.
A number of studies have published encouraging cosmetic and functional results with the HumanOptics CustomFlex® artificial iris including improvements in contrast sensitivity, glare, and cosmetic disturbance.,, Furthermore, high levels of patient satisfaction have been reported., Visual acuity outcomes are highly variable with some patients experiencing an improvement in vision, others a decline, and others experiencing no change. However, it is worth noting that visual acuity outcomes are often confounded by the high prevalence of ocular comorbidities and previous trauma in study eyes.
Accurate centration of the artificial pupil appears to be an important determinant of overall esthetic satisfaction, and even small degrees of pupillary decentration (as little as 0.35 mm) may have a significant bearing on the overall aesthetic results. It is therefore important for surgeons to pay particular attention to pupil centration during iris reconstruction. The artificial iris color has been found to be slightly brighter than the reference eye and it may be that the artificial iris appears brighter in vivo when reviewed through the cornea and aqueous rather than when dry in air. Conversely, minimal differences in hue between the artificial iris and reference eye have been observed in practice suggesting that the hand-painting manufacturing process provides a reliable, acceptable color-match [Figure 5].
|Figure 5: This is the same case as Figure 4, 1 day postoperatively, showing repair of a large iris defect in the right eye following lens extraction and insertion of an intraocular lens and a HumanOptics® artificial iris into the capsular bag. Visual acuity was 6/9 unaided and patient was pleased with cosmesis|
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A wide spectrum of postoperative complications has been reported in association with artificial iris insertion. These include elevated intraocular pressure, recurrent bleeding, capsular fibrosis, trauma to residual iris, decreased endothelial cell count, corneal decompensation, cystoid macular edema, device dislocation, and retinal detachment., Retraction (iris retraction syndrome) and darkening of the residual iris have also been described. Therefore, it is not a procedure to be undertaken lightly and patients need to be well-informed about possible short and long-term complications.
In a study of 51 patients treated with the artificial iris, a quarter (25.5%) developed unexpected events from which the majority were classified as a severe complication (retinal detachment, corneal decompensation, glaucoma, synechiae, and device dislocation). Interestingly, the complication rate decreased from 83.3% (5 of 6 implantations) in the 1st year to 13.3% (2 of 16 implantations in the 4th year of the study. In light of this significant learning curve, the technique is not recommended in low-volume settings.
However, it is important to interpret these complications in the context of the concurrent ocular comorbidities which are often present in eyes requiring an artificial iris. Furthermore, the mode of implantation exhibits a gradient of complexity as artificial irides requiring scleral suture fixation techniques are significantly more challenging than those where the implant may be placed into the sulcus or capsular bag. Early reports suggest that the latter two techniques may be associated with comparable intraoperative and postoperative complications to those in standard IOL implantations.
| Conclusion|| |
Surgical techniques for iris rehabilitation are dictated by the morphology of the iris defect and the functional complaint of the patient. Careful patient selection and counseling are paramount. Successful iris prosthesis insertion requires precision and significant surgical experience, particularly in cases where suture fixation is mandated. These cases are perhaps best concentrated in higher volume centers. The surgical reconstruction of eyes with iris defects is almost invariably complex and challenging. Nonetheless, endowed with the modern surgical armamentarium, the reconstructive surgeon may achieve significant functional and cosmetic improvement.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]