Paediatric cataract surgery

Authors


Charlotta Zetterström
Eye Department
Ullevål University Hospital
University of Oslo
0407 Oslo
Norway
Email: charlotta.zetterstrom@medisin.uio.no

ABSTRACT.

Bilateral congenital cataract is the most common cause of treatable childhood blindness. Nuclear cataract is usually present at birth and is non-progressive, while lamellar cataract usually develops later and is progressive. Prompt surgery has to be performed in cases with dense congenital cataract: if nystagmus has developed, the amblyopia is unfortunately irreversible. A treatment regime based on surgery within 2 months of life, combined with prompt optical correction of the aphakia and occlusion therapy with frequent follow-up, have been successful in both unilateral and bilateral cases. The surgery ought to include anterior and posterior capsulorexis in all children at the present time. Intraocular lens implantation has been safely performed below the age of 1 year and has also been successfully performed in bilateral cases. Anterior dry vitrectomy should be performed in preschool children to avoid visual axis opacification. Visual axis opacification is the most common complication found after cataract surgery in children. Secondary glaucoma is by far the most sight-threatening complication and is, unfortunately, common in the newborn so lifelong follow-up is essential in these cases.

Introduction

Cataract surgery in children has improved dramatically in recent decades. This is mainly because of modern surgical techniques and improved intraocular lenses (IOLs). A better knowledge of irreversible deprivation amblyopia and its treatment is also important (Taylor et al. 1979; Jacobson & Mohindra 1981).

The prevalence of childhood blindness is 0.17% in southern India. Refractive error caused 33% of visual impairment, while preventable causes such as vitamin A deficiency and cataract-related amblyopia caused 16.6%. Remaining blindness includes congenital eye anomalies and retinal degeneration (Dandona & Dandona 2003). Fortunately, cataract and aphakia are becoming less important in terms of childhood blindness in some developing countries, such as India (Foster et al. 1997; Gogate et al. 2007). It appears that girls are more likely to have a poorer outcome than boys in these countries, while being a boy predicts better short-term follow-up (Eriksen et al. 2006). In Sweden, the incidence of all cases of congenital cataract was reported to be 36 per 100 000 births (Abrahamsson et al. 1999). This figure is approximately the same as that reported in the UK (Rahi & Dezateaux 2001).

Aetiology

In developed countries, the cause of congenital cataracts is, in most cases, idiopathic. About one third of cases are hereditary without a systemic disease (Merin & Crawford 1971; Bardelli et al. 1989). These cases are mostly autosomal dominant (Wright et al. 1995). Metabolic disorders such as galactosaemia and hypocalcaemia are rare causes of childhood cataracts (Beigi et al. 1993). Congenital cataracts can be combined with systemic abnormalities such as trisomy 21 and Turner’s syndrome. Learning disabilities may be associated with bilateral congenital cataract, and there are many inherited disorders (Lambert 1997). Many genes involved in cataractogenesis have been identified (Reese et al. 1987; Armitage et al. 1995; Francis et al. 2000; Kramer et al. 2000; Li et al. 2006b). Cataract is also found in children with foetal alcohol syndrome (Stromland 2004).

A number of intrauterine infections (toxoplasmosis, rubella, cytomegalic inclusion disease, herpes infection, varicella and syphilis) may cause congenital cataracts (Nahmias et al. 1976; Cotlier 1978; Nelson et al. 1984; Lambert et al. 1989b; Wright et al. 1995). Maternal infection with rubella in the first trimester is still an important cause and the visual prognosis of surgery in these children is poor because of other ocular and associated systemic disorders and postoperative complications (Vijayalakshmi et al. 2003). For this reason it is important to continue the immunization of children, particularly in developing countries (Sharan et al. 2006).

Ocular conditions such as aniridi (Fig. 1), iris coloboma, Peters’ anomaly and lens coloboma (Fig. 2) are often seen together with cataract (Nelson et al. 1984).

Figure 1.

 Newborn child with aniridi and incipient lamellar cataract.

Figure 2.

 Child with lens coloboma and cataract.

Unilateral congenital cataract is, as a rule, not associated with systemic disease, is rarely inherited and in the majority of cases the cause is idiopathic. Some of the cases are associated with lenticonus/lentiglobus and persistent foetal vasculature (Fig. 3) (Wright et al. 1995). This condition may also be masked bilateral cataract because of asymmetric lens involvement. In a clinically healthy child with one parent affected by the disease, and also in unilateral cases, a preoperative investigation is not necessary to establish a cause for the cataract.

Figure 3.

 Newborn child with unilateral cataract and posterior persistent foetal vasculature.

Morphology

Nuclear cataract

Nuclear cataract is usually present at birth and is non-progressive (Fig. 4) (Parks et al. 1993). In cases with dense cataracts present at birth, where early surgery is mandatory, the cataracts are usually of the nuclear type. The opacification is located in the embryonic and foetal nuclei between the anterior and posterior Y sutures, and is usually very dense in the centre. The eyes are almost always smaller than normal eyes (Kugelberg et al. 1996b). In animal studies it has also been found that removal of the crystalline lens at an early age reduces eye growth, regardless of whether the animal has a good retinal image or not (Wilson et al. 1987; Kugelberg et al. 1996a). The cataract is bilateral in about 80% of cases. For individuals with bilateral congenital nuclear cataract, inheritance can be demonstrated in 30–50% of cases. The inheritance is mostly autosomal dominant, with one of the parents affected.

Figure 4.

 Infant with bilateral nuclear cataract, dense in the centre. Surgery should be performed.

Posterior cataract

Posterior unilateral cataracts in infants and children are commonly associated with persistent foetal vasculature (PFV) and the affected eye is usually microphthalmic (Fig. 5). The retrolental vascular structure in contact with the lens capsule may give way to blood vessels encircling the lens causing haemorrhage, particularly during surgery. The fibrovascular stalk may cause tractional retinal detachment. After early surgery, secondary glaucoma is unfortunately a common complication in these eyes (Lundvall & Kugelberg 2002).

Figure 5.

 Posterior cataract in a child.

Cataract associated with posterior lenticonus or posterior lentiglobus usually develops after the critical period of visual development. It is mostly unilateral and occurs sporadically. The change in the lens develops as a small defect in the posterior lens capsule, which exhibits a progressive bowing resulting in a posterior bulging and disorganization of the subcapsular lamellae and opacification. It is important to be aware of the weakness of the posterior capsule in these eyes during surgery and avoid hydrodissection, if possible. A pre-existing posterior capsule defect in cases with congenital cataract is a challenge to the surgeon and it is important to detect this before surgery (Vasavada et al. 2004a).

Lamellar cataract

Lamellar cataract usually develops after the establishment of fixation. It is usually progressive and surgery with implantation of IOLs is often performed before school age, but the cataract can remain subclinical for many years (Fig. 6). The cataract involves the lamellae surrounding the foetal nucleus peripheral to the Y sutures (Parks et al. 1993). Eyes with lamellar cataracts are usually of normal size with normal-sized corneas. The condition is uniformly bilateral and commonly has an autosomal-dominant pattern of inheritance.

Figure 6.

 Dense bilateral lamellar cataract in a 6-year-old child.

Other morphological types of cataracts

There are some other morphological types of congenital cataracts. Some are the result of lenticular developmental defects present at birth. These may have little influence on vision. Such defects are sutural cataract (Fig. 7) and anterior polar cataract (Fig. 8), which usually do not progress (Arkin et al. 1992). The main risk factor for amblyopia in congenital anterior lens opacities is anisometropia and – surprisingly – not the diameter of the cataract (Ceyhan et al. 2005).

Figure 7.

 Sutural cataract.

Figure 8.

 Anterior polar cataract in a newborn child. Surgery can wait.

Congenital cataracts

Screening for congenital cataract is cost effective and is preferably performed in the maternity ward, because it leads to early detection and surgical intervention (Magnusson et al. 2003; Magnusson & Persson 2005).

Amblyopia is caused by abnormal structural and functional evolution of the lateral geniculate nucleus and the striate cortex because of abnormal visual stimulation during the sensitive period of visual development. Reversibility of amblyopia depends on the stage of maturity of the visual system at which abnormal visual experience began, the duration of deprivation and the age at which therapy was instituted. The most critical period is probably when the patient is younger than 2 months (Wright 1995). Visual deprivation during this period usually causes severe and permanent visual loss and permanent nystagmus if not managed properly. If visual deprivation occurs after the age of 2–3 months, amblyopia is usually reversible to some extent and nystagmus is not present. The sensitivity to amblyopia then gradually decreases until the age of 6 or 7 years, when visual maturation is complete and the retinocortical pathway and visual centres become insensitive to abnormal visual input (Dutton et al. 1990). It is therefore essential to institute early treatment of dense congenital cataract in order to avoid irreversible amblyopia and nystagmus (Taylor et al. 1979; Rogers et al. 1981; Rice & Taylor 1982; Dutton et al. 1990; Kugelberg 1992).

Visual loss and the development of amblyopia also depend on the size and location of the cataract and particularly on its density. If the opacities are large enough to obscure the fundus view through an undilated pupil, amblyopia development can be expected. If retinal details such as the larger vessels can be distinguished through the central portion of the cataract, conservative treatment can be considered. Some infants with partial subclinical congenital cataract develop sufficient binocular interaction and form vision to allow a normal maturity of the visual system. Children with partial cataract treated conservatively must be followed closely. Occlusion therapy is necessary in unilateral cases to prevent amblyopia. The clinical evaluation should entail evaluation of visual behaviour including monocular and binocular fixation patterns.

Preoperative examination, congenital cataract

A careful preoperative examination of the eyes is essential: the more central and posterior the location of the opacity, the more visually significant it will be (Lambert & Taylor 1989a). The red reflex should first be assessed by direct ophthalmoscopy with the pupil undilated. The cataract is often most dense in the central part of the lens; after dilatation it seems to be less significant. Dense central opacities greater than 3 mm in diameter usually require surgical removal (Arkin et al. 1992). It is important to examine both eyes and conclude if the cataract is bilateral or unilateral. Unilateral congenital cataract presents a challenge because even a mild cataract will cause irreversible deep amblyopia in the affected eye if it is not treated (Fig. 9). In these children, vision in the affected eye is prevented from developing through active suppression by the non-affected eye (Birch et al. 1998).

Figure 9.

 Five-month-old child presented with a smaller eye with unilateral cataract and strabismus.

While the newborn child is awake it is also important to assess visual function, if possible with a clinical preferential looking grating acuity (Teller acuity card). It is also important to look at the ability to fixate and follow, and ask the parents if they have had any visual interaction with the child. Children with significant bilateral congenital cataracts may seem to have delayed neurological development as well as obviously impaired visual behaviour. In contrast, children with monocular cataracts often present with strabismus, which may not develop until irreparable visual loss has occurred. Because their visual behaviour may be unaffected, children with monocular cataract are almost always detected much later than cases with bilateral cataract. Moreover, in most cases with monocular cataract there is no family history and the children are otherwise healthy. The presence of manifest nystagmus at the age of 2–3 months or more generally indicates a poor visual prognosis (Rogers et al. 1981; Gelbart et al. 1982; Parks 1982; Kugelberg 1992). The absence of preoperative nystagmus is actually a better predictor of a good visual outcome than the age at surgery (Lambert et al. 2006).

Complete examinations of infants often require sedation or general anaesthesia and can often be performed during the same anaesthesia as the surgery. Both eyes should be examined with dilated pupils because malformations in the non-cataractous eye are commonly found (Lewis et al. 1992). Anterior segment examination is carried out with measurements of the corneal diameter and intraocular pressure (IOP) by Tonopen or hand-held Perkins tonometer. IOP is much lower in the newborn than in the adult, and is often below 10 mmHg. If the clarity of the media permits, indirect ophthalmoscopy may reveal persistent foetal vessels or any other posterior segment abnormalities that may have an impact on the visual outcome (Parks et al. 1993).

As mentioned earlier, surgery for visually significant cataract should be carried out early but the ideal time – i.e. that which results in the fewest complications and maximal visual outcome – is not identified with certainty (Forbes & Guo 2006). If the cataract is unilateral it is more important with early surgery to obtain some useful visual acuity in the affected eye. A treatment regime based on surgery within 2 months of life, prompt optical correction of the aphakia combined with occlusion therapy and frequent follow-up has been successful in several series, including unilateral cases (Cheng et al. 1991; Kugelberg 1992; Birch & Stager 1996).

Developmental cataract

If the cataract was incomplete at birth, close follow-up by a paediatric ophthalmologist is advised. Visual acuity should be followed, if possible, with clinical preferential looking grating acuity. As for the congenital cases, it is in these cases also important to look at the ability to fixate and follow and ask the parents if they have visual interaction with the child. Examination of strabismus and binocular functions are also important. Visual acuity can be measured with greater reliability in older children. Above the age of 4 years, most children could be examined with letters and monocularly. In children, both visual acuity and the development of amblyopia have to be considered. If a child has unilateral cataract or a denser cataract in one eye, surgery or occlusion therapy has to be considered. Most children with congenital cataract have small eyes; hyperopic glasses should be prescribed if needed (Kugelberg et al. 1996b).

Currently, surgery in children has almost the same indications as for adults. As in adults with cataract, impaired visual acuity and problem with glare and halos are important factors when considering surgery (Fig. 10). However, if the cataract is dense, children below the age of 7 years will develop amblyopia, which means that surgery should be performed quite soon. In older children, both eyes can be operated on during the same surgical intervention or in two sessions because the development of amblyopia is not as rapid as in younger children. In most cases it is acceptable to wait 1–2 months between surgery on each eye. Before the intervention, the child and parents have to be informed that accommodation will be lost after the surgery and that spectacles (often bifocal) are needed when an IOL is implanted.

Figure 10.

 Child with severe visual impairment and glare problems because of bilateral dense cataract.

Surgical technique in children

In infants with bilateral cataracts, it is advantageous to perform surgery in both eyes at the same surgical intervention. Most of these children are only a few weeks old, and they are extremely sensitive to the development of amblyopia. If both eyes are operated on at the same time, sterility must be maintained during the whole procedure: changing all instruments and sterile clothing of the surgeon and nurse are advisable between surgery on each the eye.

In developed countries, most surgery on children is performed under general anaesthesia. In many developing countries with scare resources, children are operated on under an effective form of narcosis called ‘neurolept anaesthesia’, which is a combination of ketamine, atropine and bensodiazepine given intravenously followed by a peribulbar injection of anaesthesia (Fig. 11). In children above the age of 7 years, only peribulbar anaesthesia is used frequently in these countries (Fan et al. 2006).

Figure 11.

 Children with their mothers after cataract surgery under ‘neurolept anaesthisia’ in a camp in India.

Lens removal

The lens can be approached through the limbus or the pars plana (Goldberg & Peymann 1983; Tablante et al. 1988). Using the limbal approach, a high-viscosity ocular viscosurgical device (OVD) is preferable because the anterior chamber is often shallow and high vitreous pressure is present. If the pupil is small, which is rather common in eyes with congenital cataract, flexible iris retractors can be very helpful; four of them are placed in the pupil before the continuous anterior capsulorexis is performed (Fig. 12). If the cataract is very dense and grey, staining of the anterior capsule with dye makes the anterior capsulorexis much easier and also safer to perform (Saini et al. 2003). The dye can be administered with a blunt syringe below the OVD just above the anterior capsule and painted on the capsule with the end of the syringe. Using this method a very small amount of the dye is needed and only the capsule is stained. Using a small amount of dye and keeping it away from the corneal endothelium is important because it affects the density and viability of cells (Nanavaty et al. 2006).

Figure 12.

 Newborn child with dense cataract and small pupils after mydriatic drops.

If an IOL is implanted, the anterior capsulorexis ought to be round and smaller than the optic, and placed in the centre of the pupil (Ravalico et al. 1996; Wejde et al. 2004). The capsule is elastic in children, which makes it more difficult to perform a manual continuous capsulorhexis (Gimbel & Neuhann 1990; Kent et al. 1995). Corticocleaving hydrodissection should be carried out with caution and sometimes avoided, for example in eyes with a pre-existing defect in the posterior capsule or in eyes that have undergone trauma (Vasavada et al. 2004a). The posterior capsule is thin and fragile in eyes with posterior polar cataracts or posterior lenticonus; in these eyes, hydrodissection should be performed with great caution (Osher et al. 1990; Vasavada & Singh 1999).

In most cases, it is possible to remove the nucleus and cortex with irrigation and aspiration; heparin can be used in the balanced salt solution (BSS) to minimize inflammation after surgery (Kohnen et al. 1998). However, with very dense nuclear cataracts and white calcified parts in the nucleus, ultrasound sometimes has to be used. AquaLase liquefaction using a warm-water stream – a new technique – would probably be very useful when removing these dense cataracts (Mackool & Brint 2004). It is important to remove all lens material to minimize postoperative inflammation, which is very pronounced in the youngest patients. To reduce opacification of the visual axis after surgery, removal of most lens epithelial cells is important; however, this is almost impossible with the technique used routinely today. The cells then migrate and proliferate from the anterior capsule and equator of the lens capsule onto the posterior capsule (Marcantonio & Vrensen 1999).

Techniques to prevent visual axis opacification (VAO)

To diminish after-cataract in children, most cataract surgeons perform posterior capsulorhexis at surgery (Zetterstrom 1997; Er et al. 2000; Ellis 2002; Jensen et al. 2002). It is usually performed through the main incision but through pars plana is also an option (Alexandrakis et al. 2002). In children, after-cataract will occur in almost 80% of eyes with an intact posterior capsule (Hosal & Biglan 2002). High-viscosity OVD is injected to fill the capsular bag; a posterior continuous capsulorexis is performed with a cystotome and is completed with forceps by frequent grasping and regrasping of the flap. The size is usually slightly smaller than the anterior capsulorexis. In this way, the posterior capsulorexis is completed safely with minimal disruption of vitreous face (Dholakia et al. 2006). The posterior capsule is thinner than the anterior capsule and not so elastic. Sometimes fibrotic parts are found in the posterior capsule, which makes tearing impossible and scissors have to be used. It is wise to look for persistent foetal vasculatures, particularly in unilateral cases with posterior cataract. Unfortunately, the outcome is poor in cases with PFV (Cheng et al. 2004). Persistent hyaloid artery is adherent to the posterior aspect of the lens and optic disc. If present it ought to be cut with fine scissors. Sometimes the vessel contains blood but cautery is seldom indicated. Using this method it is possible to implant an IOL in the capsular bag at the primary surgery or in the ciliary sulcus if a secondary implantation is scheduled in the future. Capsular fixation is preferred over ciliary sulcus placement because complications such as pupillary capture and IOL decentralization are more common with ciliary sulcus fixation (Fig. 13) (Pandey et al. 2001).

Figure 13.

 Intraocular lens implanted in the sulcus with pupillary capture and visual axis opacification.

It is debatable whether or not an anterior vitrectomy should be performed at primary surgery (Dutton et al. 1990; Buckley et al. 1993; Basti et al. 1996; Koch & Kohnen 1997; Vasavada & Desai 1997; Fallaha & Lambert 2001). It can be performed through the pars plana, or through one or two limbal incisions (Buckley et al. 1993; Vasavada & Desai 1997; Kugelberg & Zetterstrom 2002). When performed through the main incision, it is wise to leave the OVD in the anterior part of the eye after the IOL implantation, move the IOL with the second instrument and perform a dry anterior vitrectomy. When the anterior vitreous is removed, the lens epithelial cells (LECs) most often cannot grow on the remaining vitreous. This technique seems to be a good way of preventing the formation of after-cataract, particularly in preschool children (Jensen et al. 2002; Vasavada & Desai 1997; Kugelberg & Zetterstrom 2002; Ram et al. 2003; Kugelberg et al. 2004a). Complication such as cystoid macular oedema is not found in the early postoperative period, even if anterior vitrectomy is performed during surgery (Kirwan & O’Keeffe 2006b).

Resorbed cataracts

In countries with limited resources, dense congenital cataracts are not always operated on during the first years of life. These cataracts often become resorbed with fibrotic parts in the anterior capsule, and it is very hard or impossible to perform a manual anterior capsulorexis (Fig. 14). Also, a congenital defect in the posterior capsule is frequently seen in these eyes. A good option is to cut a vertical tear with scissors through both the anterior and posterior capsules, put the IOL in the sulcus and then press the optic through the tear; while the haptics remain in the sulcus, an optic capture is created. Because no nucleus or cortex remains, irrigation and aspiration are not needed in these eyes. In this way a good centralization of the IOL is achieved and a vertical almond-shaped opening in both capsules is created.

Figure 14.

 Eight-year-old boy with resorbed cataracts. The cataract is typically white in the centre and has clear zones in the periphery.

Optic capture

Another optic capture that has been studied is when the IOL is pressed through the posterior capsulorhexis, while the haptics remain in the bag. This is performed to prevent VAO (Gimbel & DeBroff 1994; Gimbel 1996; Gimbel 1997; Argento et al. 2001; Vasavada et al. 2001). However, this technique does not seem to fully prevent the formation of after-cataract: it is reported that the anterior vitreous face becomes semiopaque and opacification of both the anterior and posterior IOL surfaces can occur (Vasavada et al. 2001; Koch & Kohnen 1997). Optic capture might be a good technique in some cases because it provides a good centralization of the IOL, which is necessary in cases after trauma or an incomplete capsulorhexis (Vasavada & Trivedi 2000). Optic capture through the anterior capsule can also be performed in cases with IOL implantation in the sulcus for good IOL fixation. However, optic capture is very hard or impossible to perform with the single-piece IOL because it does not have angulated haptics (Trivedi & Wilson 2003).

Traumatic cataracts

In cases with rather immediate cataract development after a corneal wound, the anterior capsule is often broken. The condition of the posterior capsule is unknown in most of these cases, and it is important to either avoid hydrodissection or carry it out with great caution, to prevent losing lens material into the vitreous. In cases with a blunt trauma, no perforation of the globe and rapid development of dense cataract, a damaged posterior capsule should be considered when performing the cataract surgery. While the posterior capsule is much thinner and more fragile than the anterior capsule, it can rupture without perforation of the globe.

How to avoid other complications

The OVD must be removed as much as possible to avoid elevated IOP after surgery. Sometimes the pupil is closed with acetylcholine chloride (Miochol®), and it is wise to ensure that no vitreous is present in the anterior part of the eye. The sclera is soft and elastic in children and it is hard to achieve a self-sealing incision in most cases – however, this is easier with a long tunnel. Thus, in most cases the incision should be closed with a running or horizontal 10–0 nylon or vicryl sutures. Anterior synechia formation to the wound is commonly seen in the youngest patients. At the end of the procedure, it is important to look out for contact between iris and cornea and to have a stable and continuously present anterior chamber. Iridectomy is not necessary in these eyes, even when the eye is left aphakic. However, the lens capsule has to remain in the eye; otherwise, it is wise to perform an iridectomy to avoid IOP spikes.

Endophthalmitis is one of the most serious complications after intraocular surgery in children, with an incidence similar to that observed following adult cataract surgery (Wheeler et al. 1992). Prophylactic antibiotics are usually recommended in children. Perioperatively and at the end of surgery, injection of 1 mg cefuroxime in 0.1 mL saline 0.9% into the anterior chamber is an effective and safe method of avoiding infection (Montan et al. 2002a; Montan et al. 2002b; Barry et al. 2006). This regime effectively prevents the spread of gram-positive bacteria species, which are by far the most common bacteria. Prophylactic application of vancomycin into the irrigating solution during cataract surgery is not routinely recommended because of the increased incidence of cystoid macular oedema and the risk of emerging resistance to the antibiotic (Axer-Siegel et al. 1999).

Anti-inflammatory treatment should start early after surgery, and a perioperative subconjunctival injection of a long-acting steroid is recommended at the end of the surgical procedure. The use of a protective patch in children is not necessary after surgery, and there are no reported disadvantages with such a regime. On the contrary, the child can immediately begin the amblyopia treatment and parents are very pleased that they are able to establish visual interaction with the child soon after surgery.

IOL power and model

When to implant an IOL

Insertion of implants at the time of surgery before 1 year of age is now a safe and accepted practice for many surgeons (Gimbel et al. 1997; Zetterstrom 1997; Zwaan et al. 1998; O’Keefe et al. 2000; Peterseim & Wilson 2000; Nihalani & Vasavada 2006). In developing countries, good results are achieved following IOL implantation (Gradin & Yorston 2001; Yorston et al. 2001). In unilateral cases implanted with an IOL, compliance and binocularity are improved compared to contact lens correction (Greenwald & Glaser 1998; Birch et al. 2005).

In younger children, IOL implantation is more controversial. Recently, several studies have reported children below 1 year being implanted with IOL at the primary intervention. VAO is the main complication, but the glaucoma incidence seems to be lower compared to eyes left aphakic (Gouws et al. 2006; Kugelberg et al. 2006a; Lundvall & Zetterstrom 2006). In unilateral cases operated on at only a few weeks old, primary implantation is a possible option (Vasavada & Chauhan 1994; Lambert et al. 1999; Lambert et al. 2001). Unfortunately, the visual outcome is poor in most unilateral cases because of amblyopia (Lundvall & Zetterstrom 2006). Capsular bag growth does not continue after lensectomy, which is of importance when selecting lens implant (Wilson et al. 1994). In this age group, deprivation amblyopia is by far the greatest problem. Aiming for close to emmetropia at surgery is therefore most appropriate in unilateral cases, and some remaining hyperopia can be corrected with contact lenses. Refraction will change considerably during the subsequent years and the eye will become highly myopic, but hopefully not highly amblyopic. Corneal refractive surgery, piggyback implantation or implanted contact lenses are all different options for the future correction of the myopia. It is also important to realise that a child with unilateral cataract will probably not develop stereopsis and will not suffer from anisometropia. IOL power calculation is satisfactory in the young eye with the exception of children aged less than 36 months or children with an axial length less than 20 mm (Tromans et al. 2001). However, predicting future myopic shift for a given child is difficult, especially in younger patients (Plager et al. 2002).

In bilateral cases, the goal is to start with hypermetropia in childhood that will then convert into emmetropia or mild myopia in adulthood (Dahan 2000; Xie & Huang 2006). The amount of hyperopia will differ depending on the age at surgery. It is important to inform the child and parents before the surgery that the child will probably need bifocal glasses for the rest of her or his life.

Many factors are important to ocular growth in the child’s eye: for instance hereditary factors, IOP, visual acuity and IOL implantation. Rate of axial growth is more pronounced in young pseudophakic children than in older children. Unilateral pseudophakia revealed accelerated growth compared to bilateral pseudophakia (Vasavada et al. 2004b). One possible explanation could be the higher degree of amblyopia in the unilateral cases, but surprisingly VAO does not influence the rate of axial growth.

Which IOL to implant

A foldable acrylic hydrophobic IOL implanted in the young eye allows fewer complications and has therefore – at least in developed countries – replaced the polymethyl methacrylate (PMMA) IOL that was commonly used previously (Wilson et al. 2001; Wilson et al. 2003; Rowe et al. 2004). PMMA IOL is still the most commonly used lens in developing countries and it is by far the cheapest. The heparin-surface-modified (HSM) PMMA IOL has greater biocompatibility than the unmodified PMMA IOL in the young eye (Basti et al. 1999). However, the AcrySof IOL is a better choice for paediatric patients compared to HSM PMMA IOL in terms of after-cataract (Hollick et al. 1998; Kugelberg & Zetterstrom 2002). Minimizing the incision size with a foldable IOL will also result in less postoperative inflammation and astigmatism (Laurell et al. 1997). The three-piece AcrySof IOL can be deformed in small eyes, causing occlusion of the pupil: surgeons should be cautious in implanting this IOL in the eyes of newborns or in eyes with severe microphthalmus (Lundvall et al. 2003). By using a single-piece acrylic IOL and the Monarch injector, the incision size can be minimized to 2.75 mm (Trivedi & Wilson 2003). This is also a very soft IOL and therefore is probably suitable for the small eyes of the newborn baby when implanted in the capsular bag (Kugelberg et al. 2004b). Problems such as breakage of the haptics and impaired ocular growth have been found with earlier-generation IOLs implanted in the newborn monkey and rabbit eye (Lambert et al. 1995a; Kugelberg et al. 1997). The single-piece AcrySof is not recommended for sulcus fixation. Unlike the three-piece design, the haptics are thick and not angulated. Years after surgery, decentralization and iris chafing can occur with the single-piece AcrySof IOL implanted in the sulcus. An IOL with a yellow filter removing the harmful blue light is probably most advantageous for the pigment epithelium and the retina in the paediatric eye (Nilsson et al. 1989).

Another option is to implant a hydrophilic acrylic IOL. However, several studies have found more posterior capsule opacification (PCO) formation in eyes implanted with this material compared to the hydrophobic option (Heatley et al. 2005; Kugelberg et al. 2006b). Moreover, hydrophilic biomaterials implanted in the child’s eye have been investigated: calcified deposits similar to those found in adults with the same IOL have been demonstrated (Kleinmann et al. 2006).

Silicone IOLs have also been implanted in the young eye in a small number of cases with good results. However, capsule contraction is more often found in eyes implanted with a silicone IOL (Cochener et al. 1999; Pavlovic et al. 2000).

The use of a multifocal IOL should not be considered in young children with a growing eye. The axial length increases during life from a mean of approximately 16.8 mm at birth to 23.6 mm in the adult, with very rapid growth during the first 18 months (Larsen 1971a, 1971b). The mean refractive power of the cornea decreases from about 51 dioptres at birth to 45 dioptres at 6 months of age, and to 43.5 dioptres in adults (Gordon & Donzis 1985). Consequently, the refraction will change dramatically during childhood. Also, a multifocal IOL is more sensitive to decentralization than a monofocal IOL, which means that another surgical intervention may be required (Jacobi et al. 2001).

Anterior chamber IOL is generally not recommended in children (Ahmadieh & Javadi 2001).

Postoperative treatment

Topical treatment

Postoperatively, the eye of a child will tend to react with much more inflammation than the adult eye, particularly in darkly pigmented eyes. Systemic treatment with glucocorticoids is most often not indicated (an exception to this rule is children with uveitis). However, it is important to start the topical treatment with dexamethasone 0.1% immediately after surgery. In elderly patients, the drops are tapered over 1 month starting with four or five times per day. In the newborn, the treatment has to be more intense, starting with eight to 10 times per day and tapered over 2–3 months. In the youngest eyes and in eyes with dark brown irides, mydriatic drops (tropicamide or cyclopentolate) are administered for several weeks after surgery. Following this treatment regime, synechia formation can easily be avoided and retinoscopy is easier to perform before glasses are prescribed.

Correction of the aphakia

Immediate correction of aphakia is mandatory for the best possible visual outcome. There are different options but most children are implanted with an IOL during the primary surgery. The authors’ criteria for IOL implantation depends on age and whether the cataract is unilateral or bilateral. We implant an IOL in almost all children if the cataract is unilateral, regardless of age. In unilateral cases, the amblyopia is more severe, occlusion therapy is very difficult to perform and the child has an otherwise healthy eye. Therefore, it is easier to accept an IOL implantation in these eyes, even though there is no available IOL that really fits the small newborn eye (Lambert et al. 1995b; Lundvall et al. 2001). Secondary glaucoma also seems to diminish if an IOL is implanted, compared to if the eye is left aphakic (Asrani et al. 1999; Kugelberg et al. 2004b). In bilateral cases, we implant an IOL in children older than some months. Bilateral cases are often easier regarding contact-lens wear and treatment of the amblyopia.

If no IOL is implanted, contact lenses are best fitted in the surgical theatre; this provides immediate optical correction and prevents otherwise irreversible deprivation amblyopia. Several types of contact lenses are available. Rigid gas-permeable lenses have a wide range of available powers and have a great ability to correct large astigmatic errors. They are easy to insert and remove, but cause more foreign-body sensation than soft lenses (Amos et al. 1992). The two major soft lenses are silicone and soft hydrogel lenses. Both are suitable, but soft hydrogel lenses are less expensive; this is an important consideration because of the frequency of lens loss. Loss of lenses and fast eye growth during infancy necessitate frequent lens replacements, especially during the first 2 years of life. Frequent retinoscopy must be performed to decide the power of the lens. Most authorities recommend an overcorrection of +2.0 to +3.0 dioptres for near-sighted patients until bifocals can be tolerated, which occurs at the age of 2–3 years. The child should be provided with aphakic spectacles if contact lenses are unsuitable. In less than 10% of infants, contact lenses cannot be used because of complications such as keratitis, hypoxic ulceration, corneal pannus and corneal oedema (Taylor 1982; Levin et al. 1988; Amaya et al. 1990; Lorentz & Worle 1991).

Sometimes the desired IOL power is not available because of high hyperopia in the newborn. In these cases, a temporary contact lens could be an option because the refractive power most often changes over time. Another option is to implant piggyback IOLs at the primary surgery and remove one of the IOLs some months later. The sulcus-fixated IOL is removed when emmetropia is predicted with the IOL in the capsular bag (Wilson et al. 2001). Piggyback IOL implantation has some drawbacks: a second intervention is needed and adhesions are often found in the eyes of children. In older children implanted with an IOL, bifocal glasses are prescribed after retinoscopy and the remaining hyperopia is corrected. This is usually performed 1 month after surgery, at the latest.

Occlusion therapy

Occlusion therapy is started in unilateral cases as soon as the media is clear and the aphakia is corrected. Virtually all children with unilateral congenital cataract develop strabismus. In bilateral cases, occlusion therapy is sometimes useful if one eye is more amblyopic than the other. In cases with bilateral cataract, occlusion therapy does not usually need to be as aggressive as in unilateral cases. Close follow-up by a paediatric ophthalmologist is mandatory until the patient is 7 years of age – untreated amblyopia is soon irreversible during this time.

Postoperative complications

VAO

Opacification is the most common complication found after cataract surgery, particularly in children who have surgery under the age of 1 year (Fig. 15) (Lambert et al. 1999; Sharma et al. 1999). Even when a posterior capsulorexis has been performed, the growth of lens epithelial cells on the vitreous surface or on the back of the optic can be found some months after surgery. Performing posterior capsulorexis and dry anterior vitrectomy seems to be one way to decrease opacification in the postoperative time, as discussed earlier. An IOL implanted in the bag will decrease or prevent the formation of Sommering’s ring but it is then easier for the epithelial cells to migrate from the periphery to the centre of the pupil (Zetterstrom et al. 1996; Lambert et al. 2001). VAO with membrane formation is an unsolved problem in infants implanted with IOL and sometimes several interventions are needed (Kugelberg et al. 2006a; Lundvall & Zetterstrom 2006). Another possible way to prevent LEC proliferation in children is bag-in-the-lens implantation (Tassignon et al. 2002; De Groot et al. 2006). Identical capsulorexis are created in both the anterior and posterior capsules, and the capsules are inserted in a flange of the IOL. The cells are then captured within the remaining lens bag. Unfortunately a long and hard learning curve is needed to be successful with the technique; anterior and posterior capsulorexis have to be identical without any tears and with an exact size, or else the IOL can end up in the vitreous cavity.

Figure 15.

 Lens epithelium cells starting to grow behind the intraocular lens 1 year after surgery.

A very promising device to fight VAO in children is the Perfect Capsule, invented by Maloof (Maloof et al. 2003). We have recently tested the device’s ability to prevent PCO in young rabbits and have proved its efficacy when irrigated with 5-fluorouracil (Abdelwahab et al. 2006). We have also found it safe to use in young rabbit eyes (unpublished data).

Surgical management of VAO

If opacification occurs in the pupil, neodymium:YAG (Nd:YAG) laser capsulotomy treatment can be attempted. However, this is often inadequate in children because reformation of the opacification can be found some months later in these highly reactive eyes (O’Keefe et al. 2001). Surgical intervention is often necessary under general anaesthesia and has to be performed promptly to avoid amblyopia. High-viscosity OVD is injected through a small limbal incision into the anterior chamber to keep it stable during the procedure. Following an incision at the pars plana, a sharp thin knife is inserted behind the iris and IOL, and the membrane is divided. With dry anterior vitrectomy, the lens epithelial cells growing in the pupil and at the anterior part of vitreous are removed. At the end of surgery, the pars plana incision is closed with a suture and the OVD is removed from the anterior chamber to avoid a pressure peak postoperatively. After the procedure, topical dexamethasone is needed for some weeks.

Problems with the lens capsule after surgery, such as decentralization of the anterior or posterior capsulorexis or shrinkage of the capsular bag with phimosis of the capsulorexis, could make a secondary intervention necessary. Aspiration of LECs from the anterior capsule reduces the risk of phimosis when hydrophobic acrylic IOLs are implanted (Hanson et al. 2006).

Secondary glaucoma

Secondary glaucoma is, unfortunately, a common complication and is definitely the most sight-threatening (Asrani & Wilensky 1995; Lundvall & Zetterstrom 1999). The reported incidence varies from 15% to 58% (Chen et al. 2006; Kirwan & O’Keefe 2006a). Open-angle glaucoma is the most frequent type of glaucoma and can occur at any time from months to decades after cataract surgery (Asrani & Wilensky 1995). The highest incidence is found when the surgery has been performed early (below the age of 2 months); a much lower incidence is found when surgery has been performed over the age of 1 year (Lundvall & Zetterstrom 1999; Vishwanath et al. 2004). Eyes with small corneal size, nuclear cataract or persistent foetal vasculature are at greatest risk (Parks et al. 1993). As mentioned earlier, implantation of an IOL into the capsular bag seems to inhibit the development of secondary glaucoma (Asrani et al. 1999; Kugelberg et al. 2004b).

In the infant eye, a rise in IOP will cause epithelial oedema of the cornea, a poor red reflex, photophobia and fast regression of hyperopia or growing eye. These children must be examined promptly under general anaesthesia. Corneal oedema in children wearing contact lenses may be the result of hypoxia, and the contact lens must be removed immediately. The anaesthesia of choice is ketamine hydrochloride because it does not lower the IOP like most other anaesthetics. During the evaluation under anaesthesia, IOP, corneal diameter and axial length are measured and examination of the optic disc and retinoscopy should be performed. Both aphakic and pseudophakic children have thicker corneas compared to age-matched controls. This difference can have an effect on interpreting IOPs (Simsek et al. 2006). Acute glaucoma may develop in cases with excessive inflammation leading to pupillary block and iris bombé. A peripheral iridectomy and an anterior vitrectomy are often sufficient to solve the problem. Later on, a more chronic type of glaucoma might develop, probably because of the heavy inflammatory response after surgery leading to synechia formation in the chamber angle and a slow rise in IOP over time (Keech et al. 1989). Some eyes with secondary glaucoma can be controlled with topical medication but many will need a trabeculectomy with mitomycin C. In some cases a glaucoma shunt is also required to control the pressure (van Overdam et al. 2006).

It is important to remember that when cataract surgery has been performed during the first months of life, IOP and the optic nerve have to be controlled throughout the patient’s life (Asrani & Wilensky 1995).

Fibrinoid reaction

Because of the high degree of inflammation in children, fibrin in the pupil can be found even when an IOL with high biocompatibility has been implanted. Frequently administered topical steroids and mydriatics are helpful in these cases. In a few cases, Nd:YAG laser treatment may be needed to clear the visual axis. Posterior synechiae formation in the postoperative period is common, especially in the newborn when no IOL has been implanted.

Decentralization of the pupil

Incarceration of the iris in the wound is sometimes encountered. To avoid this complication, a rather long tunnel is recommended during cataract extraction and suture should be used to close the wound. Careful surgery is also helpful, leaving the iris without trauma. If the visual axis is covered with iris it is important to promptly reposition the iris or make a new central pupil with surgical intervention or Nd:YAG laser treatment.

Visual outcome

The visual outcome following cataract surgery depends on the age of onset, whether the cataract is unilateral or bilateral, the type of cataract, pre-existing ocular abnormalities or diseases, complications following surgery and the outcome of the amblyopia treatment. Late onset of the cataract, as in developmental or traumatic cataracts, is an important factor and has better visual prognosis than dense congenital cataract.

To achieve a good visual outcome in cases with unilateral congenital cataract, the surgery has to be performed before 6–12 weeks of age to minimize the effect of congenital unilateral deprivation (Drummond et al. 1989; Cheng et al. 1991; Birch et al. 1993; Birch et al. 1998). Also, the family has to adhere to the occlusion therapy schedule and optical correction is essential (Birch & Stager 1996; Lundvall & Kugelberg 2002). However, the optimal time for occlusion therapy is controversial. Visual acuity does not develop if the patching is insufficient (Lesueur et al. 1998). On the other hand, too intensive patching hinders the development of binocular function (Jeffrey et al. 2001). Another concern is if the patching interferes with psychological and perceptual development (Smith et al. 1991; Birch et al. 1993). A reduced patching regime to 25–50% of waking hours showed similar results concerning visual acuity when compared to a group of children patched 80% of waking hours (Jeffrey et al. 2001). Surprisingly, even in the group with unilateral cataract, an increase in visual acuity is obtained, despite the lack of postoperative correction with glasses or occlusion therapy (Agervi et al. 2006).

In the bilateral cases, a good visual outcome has been reported in several cases if the surgery has been performed before the age of 2–3 months and no serious complications have occurred (Taylor et al. 1979; Kugelberg 1992; Chak et al. 2006).

Visual outcome differs significantly by cataract type. The best results are found in cases with lamellar cataract and posterior lentiglobus, probably because they are not dense at birth and the children are older at surgery (Parks et al. 1993).

Uveitic eyes

Cataract surgery in paediatric uveitic eyes remains controversial. An even more controversial topic is whether an IOL can be implanted safely in these eyes (BenEzra & Cohen 2000). With modern techniques and IOLs with high biocompatibility, surgery and IOL implantation seems advantageous even in these eyes (Lundvall & Zetterström 2000; Kotaniemi & Penttila 2006). Treatment with systemic immunosuppressive drugs and topical corticosteroids has to be adjusted carefully before surgery, and an intraoperative intraocular triamcinolone injection can be considered (Kotaniemi & Penttila 2006; Li et al. 2006a).

Conclusions and recommendations

Prompt surgery has to be performed in cases with dense congenital cataract: if nystagmus has developed, the amblyopia is, unfortunately, irreversible. Surgery should include anterior and posterior capsulorexis in all children. IOL implantation can be performed safely above the age of 1 year, including bilateral cases. Anterior dry vitrectomy should be performed in preschool children to avoid VAO. Occlusion therapy should be initiated if amblyopia is present in one eye. Postoperative complications, such as a high rate of after-cataract and secondary glaucoma, are matters of concern in the newborn and lifelong follow-up is essential in these cases.

Ancillary