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Outcomes of prosthetic iris implantation in patients with albinism

Karatza, Ekaterini C. MD, MPA; Burk, Scott E. MD, PhD; Snyder, Michael E. MD; Osher, Robert H. MD

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Journal of Cataract & Refractive Surgery: October 2007 - Volume 33 - Issue 10 - p 1763-1769
doi: 10.1016/j.jcrs.2007.06.024
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Abstract

Functional iris deficiency may occur in congenital conditions such as albinism. Patients without intact iris pigment epithelium suffer from disabling glare and photophobia, which may also result in reduced Snellen visual acuity.1 Furthermore, implantation of an intraocular lens (IOL) alone in patients with albinism without addressing the iris pigment deficit may potentially result in worsened functional visual disability in part due to aberrations induced by light at the margin of the IOL.

Visual rehabilitation in patients with iris deficiency secondary to albinism can be maximized by iris supplementation with implantation of prosthetic iris elements during or after cataract surgery. Previous studies demonstrate favorable results2–4; however, implantation of some devices can be surgically challenging. We report the outcomes in 13 eyes of 8 patients with iris deficiency secondary to albinism that had successful implantation of an IOL and a prosthetic iris device.

PATIENTS AND METHODS

The medical records of all patients with ocular or oculocutaneous albinism who had cataract surgery and implantation of an iris prosthetic device at the Cincinnati Eye Institute were reviewed. Preoperative data collected included demographics, best corrected visual acuity (BCVA), subjective perception of glare fully or partially related to the iris deficiency, intraocular pressure (IOP) measurement, slitlamp biomicroscopy, and fundoscopy.

Cataract extraction by phacoemulsification with placement of an IOL in the posterior chamber was performed in all cases except 1 pseudophakic eye, in which an IOL exchange was performed. The endocapsular prosthetic iris devices used included the multiple-fin style 50C and 50D aniridia rings (Morcher), which have an overall diameter of 10.75 mm and a pupillary aperture of 6.0 mm and 4.0 mm, respectively (Figure 1), and the model 311 device (Ophtec), which has an overall outer iris-diaphragm diameter of 9.0 mm and a pupillary aperture of 4.0 mm (Figure 2). The Ophtec device was implanted in the sulcus. The 50C and 50D rings were designed to be inserted through a small corneal incision approximately 3.5 to 4.0 mm in length; 2 rings are implanted and rotated until the fins interdigitate to form a confluent iris diaphragm (Figure 3). The process by which the poly(methyl methacrylate) (PMMA) is made to appear black makes these devices very brittle, and care is necessary during insertion. The Ophtec model 311 device, which consists of a lens aperture and an iris device, is inserted through a 9.5 mm incision; however, it is more flexible and less prone to breakage (Figure 2). Implantation of the Morcher devices was performed in accordance with compassionate-use exemptions granted for each patient by the U.S. Food and Drug Administration (FDA) and monitored by an independent investigative review board (IRB). The Ophtec devices were implanted as part of an FDA-monitored study and similarly monitored by an independent IRB.

Figure 1
Figure 1:
The 50C and 50D multiple-fin-type devices are shown in composite. The central aperture is 6.0 mm and 4.0 mm, respectively, once the rings have interdigitated.
Figure 2
Figure 2:
The model 311 single-piece iris prosthesis device can be easily visualized through the albinotic iris in this case of tyrosinase-positive albinism. A crack in the pigment epithelial layer can be seen on the right side of the iris, indicating that some melanin is present within the iris melanosomes of the pigment epithelium. This focal pigment disruption was seen only after instillation of a miotic agent and may have been present before the surgical intervention. Although the pigment layer break is seen overlying the iris prosthesis device, the break is hard to see outside the edge of the diaphragm. Accordingly, it would have been hard to visualize preoperatively.
Figure 3
Figure 3:
A: The first 50D element is held over the albinotic eye after phacoemulsification. B: After the first element is placed in the capsular bag, the fins can be easily visualized through the translucent iris stroma. C: Appearance of the eye at the end of surgery. Note the significantly darker appearance of the iris, now with no transillumination. Purkinje 3 and 4 reflections from the anterior and posterior surfaces of the IOL can be seen, but the posterior chamber IOL edges are well covered.
Figure 3
Figure 3:
(continued)
Figure 3
Figure 3:
(continued)

The postoperative courses of the patients were recorded. Included were changes in the BCVA and glare disability, IOP, and extent of inflammation.

To evaluate the subjective degree of glare disability and photophobia, patients were asked to report their level of difficulty in bright light. At each visit, using a 4-point scale, patients were asked to grade their preoperative and postoperative glare disability and photophobia (Table 1A). When applicable, patients were asked to report their preoperative glare disability and photophobia as that which they experienced with the iris deficiency before development of their cataract.

Table 1A
Table 1A:
Glare conversion table.

Snellen visual acuity was determined using a Baylor Visual Acuity Tester (Medtronic-Solan Surgical Products). Snellen visual acuity was converted to a line score to record the number of lines gained or lost postoperatively (Table 1B). All data were tabulated using Microsoft Excel (Microsoft Corp.).

Table 1B
Table 1B:
Visual acuity conversion table.

RESULTS

The mean postoperative follow-up was 14.7 months (range 1.4 to 35 months). Table 2 shows the data for 13 eyes of 8 patients who had cataract surgery and prosthetic iris implantation. Of the 8 patients studied, 6 had oculocutaneous albinism and 2 had ocular albinism. Of the 6 patients with oculocutaneous albinism, 5 were tyrosinase negative and 1 was tyrosinase positive. Five were men and 3 were women. The ages of the patients ranged from 42 to 74 years.

Table 2
Table 2:
Data for 13 eyes of 8 patients with albinism.
Table 2
Table 2:
(continued)

The 50D type rings were implanted in 7 eyes and 50C type rings in 4 eyes. The blue Ophtec model 311 iris device (Ophtec Inc.) was used in both eyes of 1 patient. No intraoperative ring fractures occurred during implantation, and no intraoperative complications were noted.

Postoperatively, the BCVA improved in 8 eyes (61.5%), remained stable in 3 (23.1%), and decreased in 2 (15.4%). One eye subsequently developed an unrelated nonarteritic ischemic optic neuropathy 1 year after surgery with a 3-line loss of BCVA. Another eye lost vision as a result of secondary development of posterior capsule opacification. Of the 8 patients, 6 reported a subjective reduction in glare and photophobia, 1 no change, and 1 increased photosensitivity postoperatively. The implants remained well centered and stable with no evidence of migration in any case. Two patients had a history of ocular hypertension; however, their IOP remained well controlled with topical antiglaucoma medications. No new cases of increased IOP occurred postoperatively.

DISCUSSION

The term albinism comes from the Latin word albus, which means white. Garrod5 initially described this condition in 1908. Clinically, albinism presents as a pigmentation abnormality of the skin, hair, and/or eyes that involves an abnormality in the biosynthesis of melanin pigment. The process of forming melanin in the body involves many steps and may be affected by genes on 6 chromosomes.6,7 Because of the many genetic variations causing this condition, many different forms of albinism can occur.8 Albinism can be divided into 2 broad categories, oculocutaneous and ocular. Oculocutaneous albinism manifests as a deficiency of melanin pigment in the skin, hair, and eyes, whereas ocular albinism primarily affects the eyes with minimal or no skin involvement. Oculocutaneous albinism is mostly an autosomal recessive disorder, whereas ocular albinism is transmitted as a sex-linked or autosomal recessive disease. Oculocutaneous albinism is divided into approximately 10 different types. Two of the more common forms are type I (tyrosinase negative) and type II (tyrosinase positive). Individuals with type I disease have no skin or ocular pigmentation, whereas those with type II disease can develop some pigmentation as they grow older.

All forms of albinism have similar ocular symptoms and signs, although with varying degrees. These include photophobia; refractive errors; pendular nystagmus; reduced iris pigment with iris transillumination defects; foveal hypoplasia with significantly reduced visual acuity, usually in the range of 20/60 to 20/400; and abnormal decussation of the optic nerve fibers.8 The lack of melanin pigment in the developing eye apparently leads to foveal hypoplasia and abnormal routing of fibers within the optic nerves. These changes are responsible for the nystagmus, strabismus, and reduced stereoscopic vision in patients with albinism.

The management is often challenging due to underlying ocular problems. A variety of factors contribute to poor acuity in these patients; however, all patients present with reports of glare or photophobia. There may be many definitions of “glare” and many factors that may contribute to a person's perception of glare. Related clinical findings are lack of pigment within the melanosomes of iris diaphragm, retinal pigment epithelium, and choroid. The degree to which other findings, such as the macular or optic nerve hypoplasia, may have an effect on “glare” or photophobia is unknown.

Iris prostheses are intended to be implanted in the human eye to provide functional improvement for visually handicapped patients with selected iris pathology. The first prosthetic iris implantation was of a colored anterior chamber lens; it was performed in eyes with traumatic aniridia in 1964 by Choyce.9 Another English surgeon, Pearce, is credited with implanting an iris diaphragm in the posterior chamber in the 1970s. In 1994, Sundmacher et al.10–12 from Germany reported implantation of a single-piece black iris diaphragm IOL for correction of aniridia. Rosenthal reported the world's first case of small-incision endocapsular prosthetic iris implantation in 1996 (“Original Technique and Case Report: ‘True Sutureless’ Phaco Trabeculectomy with Insertion of Opaque Capsular Tension Ring in a Patient with Essential Iris Atrophy (Axenfeld-Rieger), Secondary Glaucoma and Cataract,” presented at the Baylor/Welsh Cataract and Refractive Surgical Congress, Houston, Texas, USA, September 1996); this was also the first implantation of any iris prosthesis in the United States. However, Rasch of Potsdam, Germany, an innovator in small-incision prosthetic iris devices, is credited as the first to present the use of different iris prosthetic elements in both eyes of a patient with albinism for treatment of photophobia during a combined cataract procedure (V. Rausch, MD, “Artificial Iris Implantation; the Innovator,” Video J Cataract Refract Surg 1999; Vol XV, Issue 4). Since then, other reports have described the use of the single-piece black iris-diaphragm IOL.3,13–15 We and others have published preliminary reports of the initial experience with the single-piece iris-diaphragm IOL and endocapsular prosthetic iris devices.16–18

In this series, simultaneous implantation of an IOL and 3 different prosthetic iris devices in patients with albinism and congenital iris deficiency was evaluated. Light entering the posterior segment was reduced by inserting 2 multiple-fin rings (types 50C and 50D) in the capsular bag and then rotating the rings until the fins interdigitated. Once a confluent diaphragm was created around a central opening, implantation of a foldable IOL followed. When implanted with a 6.0 mm optic, the aperture of the 50C rings is usually at the edge, or just slightly larger than the 6.0 mm optic, leaving the implant edge exposed. This design results in the possibility of creating edge glare as the light internally reflects at the edge of the optic. Of the 4 eyes in this study that received the 50C type iris ring, 3 had a reduction in glare and 1 had no change. The 50D type iris ring is designed to produce a smaller pupillary aperture size of 4.0 mm, which could cause an additional reduction in glare. Of the 7 eyes that received this type of iris ring, 4 had no glare postoperatively and 1 had reduced glare. The smaller pupil may allow less light to enter, but it is also a smaller aperture for IOL insertion. Both eyes of 1 patient had increased glare postoperatively; however, this patient had an extremely dense brunescent cataract that markedly filtered light before surgery. One might presume that although he reported increased postoperative glare, the increase was likely blunted by the prosthetic iris device and glare may have been profoundly disabling in its absence.

Theoretical concerns regarding difficulties in vitreoretinal examination and surgeries increase with decreasing pupillary diameters; however, vitreoretinal surgeons in our group and elsewhere have had satisfactory results when operating on eyes with complex vitreoretinal pathology through 4.0 mm apertures of iris prostheses in patients not within this defined study group (personal communication, 2003–2006). However, the ideal aperture for minimizing photophobia while maximizing the retinal view has not been objectively studied.

Overall, the surgeons were satisfied with the insertion of the prosthetic iris devices. The Morcher 50C and 50D style prosthetic iris devices carry the advantages of endocapsular fixation and placement through a small incision. Advantages of endocapsular fixated over sulcus or transsclerally sutured iris prostheses may include reduction in the incidence of inflammation and glaucoma and improvement in the stability of the device, provided the capsular bag is intact. However, the disadvantages of the 50C and 50D iris rings include their reputed susceptibility to fracture during insertion because of the brittleness of the black PMMA material. Furthermore, aligning the devices in the eye to produce a full iris diaphragm requires patience and dexterity. Even if this is achieved intraoperatively, there is a possibility of late misalignment with contracture of the capsular bag long after the devices have been implanted in the eye. However, the endocapsular devices remained stable within the capsular bag in this series, as described in other reports.16,18 Whether placement of the IOL is easier or preferred in front of or behind the new iris diaphragm has not been established. There may be implications for effective IOL power, depending on the IOL location chosen.

Alternatively, an iris reconstruction implant (Ophtec, Model 311) fixated in the ciliary sulcus can be implanted. The Ophtec device is available in brown, blue, and green. The main disadvantage of this single-piece iris diaphragm and optical lens is the requirement for a large incision (approximately 9.5 mm). There is a recent report of a foldable single-piece design that requires a smaller incision; the device is being implanted in Russia (I. Ioshin, et al., “Artificial Iris Update,” Video Journal of Cataract and Refractive Surgery 2007; Vol. XXIII, Issue 1). Also, HumanOptics, GmbH has developed a custom, flexible prosthesis to match the fellow eye (EuroTimes Supplement, June 2003).

Virtually all patients expressed their appreciation and satisfaction after surgery. In our study, the visual acuity and subjective degree of glare disability improved in 62.5% of cases and 75% of the cases, respectively. Improvement in Snellen visual acuity can be attributed to the removal of the cataract. However, patients consistently noted improvement in quality of vision and a marked reduction in glare after implantation of the prosthetic iris devices. Although cataract removal alone usually reduces the glare component caused by the cataract, this is not uniformly the case in the presence of iris deficiency as the optic diameter of an IOL is much smaller than that of the natural lens, leaving both an exposed edge and an area of iris deficiency. The expected result could be an increase in glare. Improvement of glare in 75% of the cases can therefore be considered an excellent result.

Complications did not occur during or after surgery. Moreover, neither glaucoma nor inflammation was a problem postoperatively in our series.

CONCLUSION

Operating on an albinotic eye presents special challenges. Implantation of an artificial iris device appears to be a safe and effective method for reducing the subjective perception of glare resulting from the iris deficiency. Although the currently available devices have limitations, prosthetic iris devices provide a novel way to rehabilitate these symptomatic eyes for which there was previously no alternative.

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© 2007 by Lippincott Williams & Wilkins, Inc.