Coloboma of the Iris, Retina, Optic Nerve, and Lens
A 42-year-old man presents with a progressive decline in visual function and a dense cataract in both eyes. He has had poor vision in both eyes, especially the left, due to retinal and optic nerve colobomata. He has iris and lens colobomata as shown in Figure 1. No phacodonesis is present. The lens is nearly brown with dense nuclear sclerosis.
The patient has decided to proceed with cataract surgery first in his left eye to determine if his decline in visual function is due to the cataract. A dilated examination of the posterior segment reveals retinal and optic nerve colobomata involving most of the inferior posterior pole, which appears unchanged.
KEVIN M. MILLER, MD
Cataract surgery for the patient’s left eye is a reasonable course of action if a decline in visual acuity or function can be documented. Before proceeding, however, it would be important to try to determine why his other eye developed a dense nuclear cataract. The case presentation does not tell of any ocular comorbidities for this eye. Is there a family history of autosomal dominant nuclear cataract? Was the patient born prematurely? Did he spend any time in a hyperbaric oxygen chamber? Did he receive a heavy dose of sunlight early in life? Are there nutritional issues?
The case presentation states that the patient has a lens coloboma. The lens is secondarily involved where there is faulty closure of the optic fissure. There is no actual loss of lens tissue as the term coloboma implies. The equator of the lens is flattened because the zonules that would normally stretch it are absent. The missing zonules may complicate cataract removal and lessen the stability of the IOL and any artificial iris devices that are implanted.
I would perform standard phacoemulsification and be careful to minimize the generation of heat and trauma to the corneal endothelium. I would place a dispersive viscoelastic over the area of absent zonules to prevent the anterior migration of vitreous and replace the agent as often as necessary. I would also gently stretch the pupil superiorly to create a more central pupillary opening.
Approximately 2 clock hours of iris tissue are missing. I would not try to close the iris defect with sutures, because doing so would be cosmetically undesirable and optically inadequate. My first choice for treating the defect would be to implant an Artificial Iris (Dr Schmidt Intraocularlinsen GmbH, SanktAugustin, Germany; distributed by HumanOptics, Erlangen, Germany; not available in the United States) in the ciliary sulcus after the IOL’s implantation into the capsular bag. I have achieved very nice cosmetic results with this device (Figure 2). My second choice would be to implant two Morcher Aniridia Rings (model 50F; Morcher GmbH, Stuttgart, Germany; not available in the United States) in the capsular bag in front of the IOL. The problem with the latter approach is that it creates a curvilinear slit aperture between the equator of the lens capsule and the periphery of the cornea through which unfocused light may enter the eye (Figure 3). With either technique, it will be necessary for an ophthalmologist practicing in the United States to obtain a compassionate use exemption from the FDA and approval from a local institutional review board before the artificial iris devices can be obtained or implanted.
MICHAEL E. SNYDER, MD
The technical challenges of this case begin with the choice of anesthetic. Almost invariably, such colobomata of the iris, optic nerve, and retina are associated with steep and deep inferior scleral staphylomata, making orbital injection hazardous. General anesthesia is the best choice.
A few iris retractors will likely be needed to allow adequate access to the superior pole of the lens in this very small anterior segment with microcornea. The phacoemulsification should use vital dye staining of the anterior capsule and frequent reinstallation of a dispersive ophthalmic viscosurgical device due to the very dense lens. A 1- to 2-clock-hour zonular defect is likely, although a standard capsular tension ring (CTR) would probably be fine in most similar cases. Preoperative intravenous mannitol can reduce the risk of vitreous gel’s prolapsing around the (likely) inferior zonular defect.
A highly flexible single-piece acrylic PCIOL will be the easiest to place within the small capsular bag.
The iris defect can and should be closed inferiorly to reduce the risks of edge-related glare and monocular diplopia from the light coming around the IOL’s margin in the aphakic space. Closure can often be achieved with a few imbricating sutures through the two inferior pillars, tied with Siepser’s knots. The pupil will then need to be enlarged and recentered, achievable either with 23-gauge intraocular curved scissors or, more easily, by sculpting using a 25-gauge vitrector handpiece on I/A-cut settings.
Intraocular carbachol will blunt the potential increase in IOP seen in such cases, because the ophthalmic viscosurgical device will usually migrate into the posterior segment around the (likely) inferior zonular breach.
DIAMOND Y. TAM, MD
The plan for this patient should involve cataract extraction, IOL implantation, repair of the iris defect, and recentration of the pupil to a more physiologic position.
Preoperatively, assessing the zonular apparatus will be important, because patients like this one often have zonular absence or weakness in the region of the coloboma. Further, because these individuals frequently have small anterior segments, I would perform a white-towhite measurement and use gonioscopy to assess the anterior chamber angle. Imaging such as anterior segment optical coherence tomography could also prove useful.
Intraoperatively, I would be prepared to use capsular dye as well as iris retractors. Also, if a relative anterior microphthalmos, a shallow chamber, or a short axial length is present, a pars plana vitreous tap may be required to deepen the anterior chamber for enhanced safety during phacoemulsification as well as protection of the corneal endothelium (Figure 4A). Although a majority of the zonules may be normal in tension and anatomy, I have a low threshold for placing a CTR in the setting of possible zonular compromise.
Although in traumatic iris defects the margins can be simply apposed and sutured, this approach results in an inferiorly decentered pupil in cases of coloboma. Relaxing incisions must therefore be made in the peripheral iris on both sides in the inferior midperiphery to allow the iris to relax superiorly so that, when the margins of the defect are apposed, the pupil will be centered properly (Figure 4B). This technique provides a superior cosmetic outcome and places the pupil in greater alignment with the corneal center (Figure 4C).
DEVESH K. VARMA, MD, FRCSC, AND IQBAL IKE K. AHMED, MD, FRCSC
The more recent progression of visual loss is likely caused by a cataract. There may, however, be reduced vision at baseline from an underlying compromise of the optic nerve and retina as well as dyscoria from the extensive coloboma. Lenticular astigmatism from subluxation of the crystalline lens can also be a factor when colobomata involve the zonules, although the absence of phacodonesis suggests this may be less of an issue here. Testing with a potential acuity meter (Marco, Jacksonville, FL) can be helpful for patients contemplating the risks and benefits of pursuing surgery in such cases. Most likely, this patient’s precataract visual acuity could be restored by cataract surgery. Combining the procedure with pupilloplasty could simultaneously address any photophobia and cosmetic concerns.
Preparation for cataract surgery in this case requires extra care. Like many colobomatous eyes, this one may be microphthalmic with a disproportionately small anterior segment (relative anterior microphthalmos). This anatomy has implications for the IOL power calculation, because the anticipated anterior effective lens position can produce a myopic result. Thus, we often aim for slight hyperopia in these eyes. Microphthalmic eyes are also at risk for intraoperative positive pressure/malignant glaucoma, so we would be prepared to execute a prior pars plana vitreous tap to create adequate working space for cataract surgery. Furthermore, because phacoemulsification in a shallow anterior chamber can place additional stress on endothelial cells, a preoperative specular microscopy study would be helpful for planning. Determining the axial length can be challenging in the presence of irregularities in the posterior pole, and we recommend optical biometry using the IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA) or Lenstar LS 900 (Haag-Streit USA Inc., Mason OH). Zonular loss in colobomata tends to be localized and can typically be managed with a CTR, usually without the need for a sutured device.
Preparation for the pupilloplasty would involve noting the patient’s degree of photophobia, particularly prior to the cataract’s progression, which can blunt these symptoms. We would also assess the iris’ color, contour, and thickness in both eyes. Finally, we would take the patient’s cosmetic goals into consideration. Testing should include slit-lamp photographs, and specular microscopy would once again be helpful, given the additional intraocular manipulation.
We would modify our surgical technique to handle a shallow anterior chamber as previously discussed. If at any time during the surgery the working space in the anterior chamber became problematic, or if there were excessive convexity of the posterior capsule, we would strongly consider a pars plana limited anterior vitrectomy to deepen the anterior chamber. In microphthalmic eyes, we have found that this positive pressure is often the single biggest challenge. We would inject a dispersive viscoelastic peripheral to the lens in the area of the coloboma to prevent vitreous prolapse. In anticipation of some (usually mild) zonular laxity, we would then cautiously create the capsulorhexis. Keeping in mind that the lens and capsular bag might be smaller than average, it would be important to maintain an anterior capsular rim of at least 2 mm to provide adequate coverage of a CTR and IOL.
At this point, viscodissection followed by early insertion of the CTR could help prevent vitreous prolapse by expanding the capsular equator over the zonular defect, avoid fluid misdirection syndrome, stabilize the capsular bag for nuclear removal, and keep the capsule in a more posterior position to counteract its tendency toward anterior displacement in a microphthalmic eye. If the zonular defect were large enough, one or two iris/capsular retractors could be placed on the capsulorhexis’ rim in the area of dialysis for intraoperative support. We would remove the nucleus and cortex while minimizing zonular stress. When changing instruments, we would use a viscoelastic or balanced salt solution to maintain the anterior chamber in an effort to prevent intraoperative malignant glaucoma or vitreous migration through the zonular coloboma. At no time should the anterior chamber be allowed to shallow for the aforementioned reasons.
After inserting the IOL, we would leave viscoelastic in the eye and create paracentesis incisions at the 4- and 8-o’clock positions in preparation for the pupilloplasty. Using a technique described elsewhere,1,2 we would make relaxing incisions followed by two or three interrupted iris sutures using 10—0 Prolene (Ethicon, Inc., Somerville, NJ) to close the coloboma and create a 3-mm round pupil (Figure 5). We prefer to use microinstrumentation such as micrograspers and microtying forceps (MicroSurgical Technology, Redmond, WA) to manipulate and suture the iris in a controlled, closed-system environment. Relaxing microsphincterotomies are important to prevent an excessively inferiorly positioned aperture after pupilloplasty. The viscoelastic could be removed using an atraumatic dry aspiration technique, again while preventing the anterior chamber from becoming shallow by exchanging it for balanced salt solution in multiple aliquots.
Postoperatively, we would recommend an extended course of topical nonsteroidal anti-inflammatory drugs to prevent cystoid macular edema.
Section Editor Bonnie A. Henderson, MD, is a partner in Ophthalmic Consultants of Boston and an assistant clinical professor at Harvard Medical School. Thomas A. Oetting, MS, MD, is a clinical professor at the University of Iowa in Iowa City. Tal Raviv, MD, is an attending cornea and refractive surgeon at the New York Eye and Ear Infirmary and an assistant professor of ophthalmology at New York Medical College in Valhalla. Dr. Oetting may be reached at (319) 384-9958; firstname.lastname@example.org.
Iqbal Ike K. Ahmed, MD, FRCSC, is an assistant professor at the University of Toronto and a clinical assistant professor at the University of Utah in Salt Lake City. He acknowledged no financial interest in the products or companies he mentioned. Dr. Ahmed may be reached at (905) 820- 3937; email@example.com.
Kevin M. Miller, MD, is the Kolokotrones professor of clinical ophthalmology at the Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles. He acknowledged no financial interest in the products or companies he mentioned. Dr. Miller may be reached at (310) 206-9551; firstname.lastname@example.org.
Michael E. Snyder, MD, is a voluntary assistant professor of ophthalmology at the University of Cincinnati, and he is in private practice at the Cincinnati Eye Institute. Dr. Snyder may be reached at (513) 984-5133; email@example.com.
Diamond Y. Tam, MD is a clinical assistant professor in the Department of Ophthalmology at Stanford University School of Medicine in California. He acknowledged no financial interest in the product or company he mentioned. Dr. Tam may be reached at firstname.lastname@example.org.
Devesh K. Varma, MD, FRCSC, is a glaucoma and anterior segment surgeon in Mississauga, Ontario, Canada. He acknowledged no financial interest in the products or companies he mentioned. Dr. Varma may be reached at email@example.com.
- Gagne S,Ahmed IA.Anterior segment surgery:iris repair.Contemporary Ophthalmology.2009;8(22):1-8.
- Cionni RJ,Karatza EC,Osher RH,Shah M.Surgical technique for congenital iris coloboma repair.J Cataract Refract Surg.2006;32(11):1913-1916.