Fig. 16.1
Congenital aniridia. (a) Congenital aniridia complicated by keratopathy. Corneal neovascularization at the limbus in a 5-year-old boy. (b) Congenital aniridia complicated by cataract in a 6-year-old girl. (c) Congenital aniridia complicated by lens dislocation in an 8-year-old girl
Iris anomalies: They are mainly bilateral. The iris is largely absent with iris stump seen under gonioscope.
Glaucoma: It is one of the most frequent complications. In the early phase, the trabecular meshwork is normal, but with physical growth and development, residue of the iris may adhere to the wall of the anterior chamber angle or trabecular meshwork, which gives rise to angle closure. Moreover, glaucoma can also occasionally arise from lens dislocation.
Lens anomalies
- 1.
- 2.
Fundus lesions: Optic nerve and macular (foveal) hypoplasia are frequent fundus changes. They might be both present as comorbidities. Children with macular (foveal) hypoplasia often have concurrent horizontal nystagmus. In addition, children with aniridia are predisposed to retinal tear and detachment.
Systemic Anomalies
- 1.
Wilms’ tumor: There are 25–33 % of pediatric patients with congenital sporadic aniridia that are complicated by this kind of renal neoplasm. The reason may be that an interstitial deletion of the short arm of chromosome 11p involves congenital aniridia and the Wilms’ tumor suppressor gene simultaneously. Wilms’ tumor, congenital aniridia, genitourinary anomalies, and mental retardation (Wilms’ tumor-aniridia-genital anomalies-retardation) are collectively termed WAGR syndrome [3, 4].
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16.1.1.2 Surgery
Preoperative Assessment
Since pediatric patients with congenital aniridia are often complicated with various ocular anomalies, it is necessary to carry out a detailed preoperative assessment.
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Identify the leading cause of children visual impairment. Since decreased visual acuity can be triggered by various factors such as lens opacification, corneal opacification, glaucoma, etc., doctors are supposed to identify the main contributing factor.
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The anatomical characteristics of pediatric eyeball, such as the condition of capsular bag and zonules, should be fully assessed when adopting surgical strategies to deal with congenital aniridia. The relatively narrow intraocular space and immature capsular bag of pediatric patients are prone to exert negative effect on the implantation of iris prosthesis and capsular tension ring.
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Assessing other coexisting factors which are related to visual acuity. As for the cases in which visual impairment is mainly triggered by cataract, other coexisting abnormalities are supposed to be fully considered when adopting appropriate treatment strategies. For example, when mild to medium corneal opacification has little effect on cataract surgery, preference should be given to cataract surgery before further treatment is considered according to corneal conditions. On the contrary, if there is severe corneal opacification which interferes with cataract surgery, corneal surgery or combined surgery is the prime option. Additionally, gonioscopy must be conducted in detail to identify whether there are anterior chamber angle anomalies. If necessary, three-mirror contact lens or an indirect ophthalmoscope may be used for fundus examination to rule out or perform prophylactic treatment to occult peripheral retinal lesions.
Selection and Techniques of Operation
- 1.
Cataract extraction and IOL implantation: Most pediatric patients with congenital aniridia combined with cataract do not show significant lens opacity at birth, and the lens opacity gradually increases with age; therefore, cataract extraction is normally conducted after 3 years old. Cataract extraction and IOL implantation are the most common surgical methods. In author’s opinion, simple cataract extraction and IOL implantation are feasible, especially when the anterior segment narrow space and lens capsular defects are found in preoperative assessment, and no iris prosthesis implantation can be used.
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Incision: The incision location, type, and size are of utmost importance to ensure smooth surgical procedure as well as desirable postoperation visual acuity. Children with congenital aniridia are often combined with corneal abnormalities. In order to avoid further damage to the cornea, reduce surgically induced astigmatism (SIA), provide operating convenience, and offer postoperative incision nursing care, the superior scleral tunnel incision is usually used, but some argue that a clear corneal incision can reduce intraoperative and postoperative bleeding [10].
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Capsulorhexis: Due to the thin and brittle nature of the anterior capsule as well as the absence of iris in congenital aniridia patients, an oversized capsulorhexis easily leads to capsular rupture. Capsulorhexis is not supposed to be larger than the optical surface of IOL in diameter [11]. Oversize capsulorhexis opening may result in significant IOL edge effect. Therefore, capsulorhexis diameter should be restrained within 4.5–5 mm [11]. Furthermore, residual anterior capsule on the periphery can alleviate photophobia in these children to some extent. Capsule staining technique can be applied intraoperatively to increase visibility.
- 3.
Hydrodissection and hydrodelineation: The anterior capsule is thin and brittle in these children, and the absence of iris eliminates the barrier between the cornea and the lens. Slow injection at multiple sites within the capsular bag is recommended. This avoids sudden elevation of pressure inside the capsule that results in capsule damage, as well as forward dislocation of the nucleus that causes mechanical damage to the cornea.
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Lens extraction: Either cataract aspiration or phacoemulsification is chosen based on the hardness of lens opacification.
- 5.
IOL implantation: By measuring the limbus white-to-white distance, the diameter of the capsular bag can be estimated; thus appropriate IOL can be selected. Under the premise of intracapsular IOL implantation, IOLs with larger optics are suggested, so that the rim of the optics can be covered by the anterior capsular, which is able to reduce IOL edge effect.
- 1.
- 2.
Iris prosthesis implantation combined with IOL implantation.
In pediatric cataract patients complicated by congenital aniridia, if simple IOL implantation is performed following cataract surgery, higher-order aberrations in the eyes with large pupils and the edge effect of IOL will be significant [12], which affects pediatric patients’ visual function. At present, a variety of pigmented materials are used as artificial iris for long-term intraocular implantation in adults, such as single piece iris diaphragm IOL, emulated artificial iris, and capsular tension ring with iris diaphragm. However, those aforementioned iris prostheses are rarely used in pediatric patients with cataract complicated by congenital aniridia. Only a few argue that those prostheses can be implanted in children with traumatic aniridia. The long-term effect remains to be observed. Problems with these devices include brittleness, low plasticity, and being liable to fracture intraoperatively and postoperatively [11, 13–15]. In addition, the implanted artificial iris and tension ring tend to give rise to a crowded capsular bag, placing a heavier load on the capsular bag, which is already weak in this case. What’s more, they may trigger complications including inflammatory response, corneal endothelial damage, glaucoma, and increase the incidence of posterior capsular opacification (PCO). Therefore, the authors think that this type of implant needs to be prudently chosen.
16.1.2 Pediatric Cataract with Iris Coloboma
16.1.2.1 Classification of Congenital Iris Coloboma
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Typical iris coloboma: It is presented as total iris coloboma inferior to the pupil. It is caused by incomplete fusion of ocular fissures and might be accompanied by colobomas of the ciliary body, the choroid, and the lens.
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Simple iris coloboma: It occurs after normal fusion of ocular fissures and is not complicated by other colobomas of the uvea. From the 1930s to the 1980s, patients with congenital cataract, particularly lamellar cataract, were often treated with optical iridectomy [16, 17]. Sector coloboma of the iris occurs mostly in the inferonasal quadrant after optical iridectomy and is easily confused with congenital iris coloboma. The main distinction between eyes with congenital iridocoloboma and those after optical iridectomy lies in the fact that the pigment collar and sphincter pupillae at the pupil edge of the former always extend from the defect zone to the limbus, whereas there is no pigment collar at the edge of the defect in the latter (Fig. 16.2).
Fig. 16.2
(a) Congenital iris coloboma. (b) Acquired iris coloboma caused by segmental iridectomy
16.1.2.2 Surgical Treatment of Congenital Iris Coloboma
Selection of Surgical Intervention
For children with congenital iris coloboma complicated by cataract, surgical techniques should be determined based on the size and location of coloboma. It is generally believed that coreoplasty can be chosen when the proportion of coloboma is less than 1/4 of the iris. When the size of coloboma is more than 1/4, tension of iris sutures becomes greater and iris tear often ensues.
For children following optical iridectomy, most of the remaining sphincter pupillae functions normally. Cataract extraction combined with IOL implantation and coreoplasty are often adopted.
Surgical Techniques
- 1.
Cataract extraction combined with IOL implantation: The surgical techniques are the same as the routine pediatric cataract extraction combined with IOL implantation (Fig. 16.3).
Fig. 16.3
Surgical procedure of congenital cataract combined iris coloboma. (a) Preoperative image shows iris coloboma from 3 to 9 o’clock (the image is upside down); (b) capsulorhexis with the assistance of trypan blue; (c) hydrodissection; (d) cortical aspiration of the remanescent lens; (e) estimation of the capsular bag size by measuring the limbus white-to-white distance; (f) IOL implantation with appropriate diameter according to previous step results
- 2.
Coreoplasty: One percent of carbachol is used for miosis in order to control suture tension. Sufficient OVD is instilled into the anterior chamber (preferably cohesive OVD) to provide space for manipulation and prevent hyphema. A 10–0 nylon suture or polypropylene suture is used. The needle is inserted through the cornea at the site of iris coloboma, and passes through the opposing iris at about 0.5 mm outside the pupillary margin, and is withdrawn from the opposing cornea. Make sure to keep off the pupillary zone. The forceps enter through the incision into the anterior chamber to knot, and the ligation is not supposed to be too tight in order to prevent iris tear. Finally, with the residual OVD in the anterior chamber cleared, one suture is placed in the incision for closure (Fig. 16.4). The postoperative management is similar to common intraocular surgery. If there is severe inflammatory response in the anterior chamber, mydriatics may be applied.
Fig. 16.4
Coreoplasty. (a) Entry and exit of suture. (b) Knot-tying in the anterior chamber
The detailed procedure of the slipknot technique for iris suture is as follows (Fig. 16.5): After the corneal paracentesis is made with a 15° blade, a long straight needle with 10–0 polypropylene thread enters from the paracentesis into the anterior chamber. It passes through opposing edges of the iris to be sutured and leaves through the opposite limbus. Since the iris itself is soft, it might be difficult for the suture needle to go through the iris. In this case, a 1 ml syringe needle can be used to fix the long straight needle to go through the iris. A forcep enters through the paracentesis and grabs onto the suture at the other end. The tail near needle insertion and the opposite suture are winded into a double knot. Both ends of the suture are tightened and the suture is knotted by itself. The second and third knots are tied and tightened in the same way, thus forming firm knots. Vannas capsulotomy scissors are inserted through the tunnel incision to snip away the end of the knot.
Fig. 16.5
Coreoplasty: suture closure of the iris performed with the slipknot technique
16.1.3 Pediatric Cataract with Persistent Pupillary Membranes
Incomplete regression of tunica vasculosa lentis during the embryonic period may result in residual iris tissue in front of the lens anterior capsule (i.e., persistent pupillary membranes). With an approximately 30–95 % prevalence in neonates, most of persistent pupillary membranes achieve complete regression within 1 year after birth, and only a few of them last for a long time.
16.1.3.1 Classification and Clinical Manifestations of Persistent Pupillary Membranes
Based on the site of occurrence, persistent pupillary membranes can be classified as those at the iris or those attached to the lens. The former originate from the iris surface, with the other end shaped like fibers, strips, or sheets and attached to the surface of the lens anterior capsule (Fig. 16.6). Localized white opacities can be seen at the site of lens attachment. The latter bear no connection to the iris and are presented as dispersed, tiny residual pigmented membranes that appear as spots or stars and are attached to the anterior capsule.
