Pars plana lentectomy for treatment of congenital cataract

Graefe’s Arch Clin Exp Ophthalmol (2001) 239:649–655

C L I N I C A L I N V E S T I G AT I O N

DOI 10.1007/s004170100315

Petra Meier Ina Sterker Peter Wiedemann

Received: 13 February 2001 Revised: 2 May 2001 Accepted: 21 May 2001 Published online: 4 August 2001 © Springer-Verlag 2001

P. Meier (✉) · I. Sterker · P. Wiedemann University Eye Hospital, University of Leipzig, Liebigstrasse 10–14, 04103 Leipzig, Germany e-mail: [email protected] Tel.: +49-341-9721567 Fax: +49-341-9721659

Pars plana lentectomy for treatment of congenital cataract

Abstract Background: Congenital cataract surgery can be performed using a pars plicata/plana or a limbal approach, if placement of an intraocular lens at the time of cataract removal is not a consideration. Because of the high incidence of secondary cataract formation in children the operation should be combined with capsulotomy and anterior vitrectomy. Methods: The series consisted of 30 eyes from 20 consecutive children who suffered from congenital cataract and underwent cataract surgery between May 1995 and June 2000. The inclusion criterion was congenital cataract affecting the visual axis. We performed the operations as lens aspiration with anterior and posterior capsulotomy and anterior vitrectomy via the pars plana or plicata. We used contact lenses to re-

Introduction A cataract affecting vision in babies and infants is always associated with development of amblyopia, so that if possible a lens operation must be performed without delay in these eyes. However, implantation of an intraocular lens (IOL) in babies and infants is controversial owing to the development-related changes in refraction of the child’s eye. Implantation of an IOL in children less than 1 year of age is possible [13], but many surgeons are reluctant to place an IOL in an eye of a child with monocular cataract who is younger than 1 year [3]. Many surgeons implant an IOL only after the end of the second year of life [9, 19, 38]. Now a multicentre clinical trial, the Infant Aphakia Treatment Study, is being or-

habilitate vision. All patients received intensive orthoptic and pleoptic treatment. Results: This surgical technique provided in all eyes a clear visual axis. During follow-up of 3 months to 4.5 years, secondary cataract developed in five eyes. Retinal detachment, glaucoma and endophthalmitis did not occur. One patient developed contact lens intolerance and a secondary intraocular lens was placed in the ciliary sulcus. Discussion: Lentectomy via a pars plana or pars plicata approach is a suitable and safe method for treating cataract in children. Our chosen method of lentectomy is an alternative to early implantation of an intraocular lens. It is possible to perform uncomplicated secondary implantation of an intraocular lens in the ciliary sulcus.

ganised in the United States to critically compare treatment with IOL versus contact lens correction for infantile aphakia [26]. In principle, in the paediatric population in whom placement of an intraocular lens at the time of cataract removal is not a consideration, an approach close to the limbus or a pars plana or pars plicata approach can be chosen for the operation. If the lens capsule is not removed in children, however, there is an extremely high probability that secondary cataract will develop. This can be prevented by complete lentectomy, but the secondary implantation then gives rise to problems. In recent years, surgical techniques have therefore been developed which enable lentectomy that is as complete as possible, leaving behind a peripheral capsular ring [4,

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Fig. 2 After aspiration of the lens, anterior and posterior capsulotomy, the irrigation cannula of the bimanual aspiration and irrigation system and the cutter are visible at the level of the pupil

Table 1 Distance of the scleral incision from the corneal limbus Age in months

Fig. 1 Histological section of a a mature neonate and b a 12-monthold child. The pars plana of a newborn baby is very short (distance between arrows) and develops quickly within the first year of life (hematoxylin-eosin; original magnification ×32)

33, 35]. We performed the operations as lens aspiration with anterior and posterior capsulotomy and anterior vitrectomy via the pars plana or plicata. In the present paper, we use the term lentectomy for this operation and we report on our results of lentectomy in 30 eyes.

Patients and methods The series consisted of 30 eyes from 20 consecutive children who suffered from congenital cataract and underwent cataract surgery between May 1995 and June 2000. The inclusion criterion was congenital cataract affecting the visual axis, i.e. if the pupil was neutral no fundus red was visible. 10 patients suffered from bilateral cataract and 10 from unilateral cataract. In all children who were referred to our hospital and had a cataract affecting their vision, the lens operation was carried out without delay within a few days. Two babies with bilateral cataract and two with unilateral cataract were operated on before the 6th week of life. All other children were referred for operation later. In cases of bilateral cataract the operation on the second eye always took place within 3–5 days of the first. Lentectomy was performed via the pars plana or pars plicata in all children (Fig. 1). Depending on the age of the patient, we made the scleral incision according to the criteria specified in Table 1. Before the scleral incision, the conjunctiva was opened immediately above the site of incision. Two scleral incisions were made, preferentially at the 11 o’clock and 2 o’clock positions. After

Distance

6 months

1.5 mm

2.0 mm

2.5 mm

scleral incision, the lens capsule was opened via the equator and the lancet was advanced until the tip was visible at the level of the pupil. A cannula connected to an infusion via a handpiece as well as a cutter was then pushed forward into the lens nucleus. The last eight eyes were operated on using the irrigation cannula of the bimanual aspiration and irrigation system (Storz). After removing the nucleus of the lens, all the cortical parts were aspirated. Finally, the posterior and anterior capsule was cut out with a cutter (Fig. 2). The capsulotomy had a diameter of about 3.5–4 mm. Vitrectomy of the anterior one third of the vitreous was then performed. After careful removal of prolapsed vitreous from the region of the scleral incisions, the sclerotomies were closed with Vicryl 7/0 and the conjunctiva with Vicryl 8/0; the knots were countersunk. Immediately after the operation, a contact lens was inserted in accordance with the corneal radii determined preoperatively with the hand keratometer. Blue light was used to check whether the contact lens was properly located. All children were provided with contact lenses (WUK-Vision). In preverbal children, visual acuity was assessed by “teller acuity cards”. Once the child was capable, visual acuity was assessed by “tumbling E’s” or Snellen letters. The contact lenses were adapted to close vision and checked every 6 weeks. In children operated on unilaterally, the partner eye was occluded for a time which comprised, on average, half of the waking period. After bilateral lentectomy, there was no occlusion treatment when there was fixation on both sides. If one eye took the lead, these children also received occlusion treatment. Progressive spectacles were fitted from the 3rd year of life.

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Table 2 Patient data Number of patients Males:females Number of eyes

20 13:7 30

Age at operation Mean Range Median Nystagmus Strabismus

13 months 6 weeks to 36 months 21 months 3 8

Table 3 Aetiology Aetiology

Number of patients

Idiopathic Hereditary

12 2

Association with ocular malformation Microphthalmos Iris coloboma

Fig. 3 The left eye of a 3-year-old child following operation of a congenital cataract after 2 years’ follow-up and secondary implantation of an intraocular lens on the rim of the residual lens capsule

1 1

Association with systemic malformation Hallermann–Streiff syndrome 1 Lowe syndrome 1 Infantile myoclonic seizures 2

Table 4 Postoperative complications Complication Secondary cataract (five eyes)

Time at onset Therapy after lentectomy

9 weeks 3 months 8 months 8 months 19 months Contact lens intolerance 3 years (one eye)

Discission Discission Discission Discission Discission Implantation of posterior chamber lens in ciliary sulcus

Results The patients’ clinical data are summarised in Tables 2 and 3. For the eyes included in this study, a follow-up of 3 months to 4.5 years (mean 31 months) was available. In all eyes the surgical technique provided a clear visual axis postoperatively. At times between 3 months and 4.5 years, secondary cataract was found to have developed in five eyes; in each case it was successfully managed by reoperation (Table 4). Retinal detachment, glaucoma and endophthalmitis did not occur. A 3-year-old child developed contact lens intolerance and a posterior chamber lens was placed in the ciliary sulcus (Fig. 3). Strabismus was diagnosed in eight patients (six children with unilateral cataract; two with bilateral cataract). Nystagmus was ob-

Fig. 4 Last corrected visual acuity in correlation to age at unilateral cataract operation (Fix = fixation; nFix = no fixation, o = mentally retarded child)

served in three patients with bilateral cataract. The bilateral lens operation was performed at the age of 8 weeks, 6 months and 3 years. Whereas the nystagmus did not regress at a postoperative visual acuity of 0.16 and 0.2 (preoperative visual acuity of R=L 0.1) in the 3-year-old child, there was a marked decrease of the nystagmus in the two babies. Figure 4 shows the best corrected visual acuity in eyes that underwent combined aspiration of the lens, anterior and posterior capsulotomy and anterior vitrectomy for treatment of unilateral congenital cataract, and figure 5 shows the best corrected postoperative visual acuity after operation of bilateral congenital cataract. One child with unilateral cataract and two of the children with bilateral

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Fig. 5 Last corrected visual acuity in correlation to age at bilateral cataract operation (Fix = fixation; nFix = no fixation, o = mentally retarded child)

cataract were substantially mentally retarded (Lowe’s syndrome; infantile myoclonic seizures), so that a precise appraisal of function could not be made in these patients. The baby with Hallermann–Streiff syndrome died 3 months after operation.

Discussion Pseudophakia in children is predicted to result in a large amount of myopic shift, particularly in very young children [29]. Children normally have a small amount of myopic shift as they grow, despite the large increase in axial length (from 16.8 mm at birth to 23.6 mm in adult life). This is because of the correspondingly large decrease in power of natural lens during this time, i.e. the natural lens power declines from +34.4 diopters to +18.8 diopters [16]. Therefore, because of the constant power of an IOL, a child with pseudophakia might be expected to experience a large myopic shift as the eye grows. Children who underwent surgery in the first 2 years of life had a significantly greater myopic shift than older children and a large variance in this shift [29]. Eye growth and refractive change are most rapid during the first 2 years of life. It would therefore follow that patients who undergo surgery at a very young age have the largest changes in axial length and refraction [13, 28, 34]. The difficulty in predicting refraction is the main disadvantage of IOL implantation. If an IOL calculated for emmetropia is implanted in the first few years of life, myopia of the eye will result after only a few months. The use of a hyperopic target refraction for an IOL is associated with the risks of amblyopia immediately post-

operatively. Owing to these difficulties in predicting the optimum refraction for an IOL, we did not implant an IOL in any patient below 3 years of age. We only used contact lenses for optical rehabilitation of aphakic eyes. In unilateral cataract, Gregg and Parks [17] stipulate that surgical lentectomy should be performed at the earliest possible date, i.e. within 24 h after birth. They report on a patient who could attain stereovision after this early operation. It is known from animal experiments that a latent phase precedes the phase of sensory adaptation of visual function in which temporary deprivation does not affect the development of normal visual function. This latent phase is 3 weeks in monkeys [32] and 12 days in cats [20]. For humans there exists a 6-week window of time, beginning at birth, during which treatment of dense congenital unilateral cataract is maximally effective. If treatment is initiated during this period and the child is compliant with contact lens wear and occlusion therapy, excellent visual acuity outcomes, i.e. visual acuity of 0.5 and better, are frequently obtained [5]. Early treatment with good compliance is also associated with a lower prevalence of strabismus and a higher prevalence of fusion and stereopsis [5, 6]. Accordingly, a dense congenital cataract should be removed within this 6-week latent phase. In all children who were referred to our hospital and had a cataract affecting their vision, the lens operation was carried out without delay. Two babies with bilateral cataract and two with unilateral cataract were operated on before the 6th week of life. All other children were referred for operation later. This explains the limited development of visual acuity in some children of our series. It must be assumed that severe deprivation amblyopia had already developed especially in unilateral cataract. The visual acuity in these eyes could not be adequately improved despite intensive orthoptic treatment. Three of the patients were also substantially mentally retarded, making precise appraisal of function impossible. Altogether, the visual results attained after operation on unilateral cataract are always inferior to the functional results after operation on bilateral cataract, since an aphakic eye cannot accommodate despite optimal correction and intensive orthoptic treatment. It thus loses out in the binocular competition with the other eye. The majority of children attained a maximum vision of 0.1 [4, 31] after operation of an unilateral cataract and contact lens correction. In exceptional cases, better functional results have been described [17, 28, 39]; only 8–24% achieve visual acuity of 0.5 and better [4, 31]. It must also be taken into consideration that a proportion of the children had already developed unilateral cataract at the time of birth, and that this only gradually developed to become a relevant optical handicap. This explains why the children we operated on attained vision between 0.1 and 0.3 after the first year of life even after an operation for unilateral cataract. Lambert [26] reviewed the long-term results after monocular IOL implantation in 23 infants less than 6

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months of age. In summary, the 23 monocularly pseudophakic infants with 2 years and more follow-up whose cases had been reported in the literature had a mean visual acuity of 20/60, i.e. 0.3 (minimum 20/200 to maximum 20/30). These data show a better visual outcome for children with IOL correction than for contact lens correction. Now the Infant Aphakia Treatment Study is being organised to critically compare a treatment with IOL versus contact lens correction for infantile aphakia [26]. The results of this study will help us to evolve guidelines for the use of contact lenses or IOL in children for correction of aphakia. If there is bilateral cataract of the same severity with a good view into the fundus, one can wait before removing the lens, since there is no acute danger that severe deprivation amblyopia will develop. If the lens opacities are unequal, the eye with the more pronounced cataract should be operated on first, since according to Crawford [10] the eye with the greater lens opacity achieves better vision postoperatively than the partner eye. If bilateral cataract surgery is indicated, an interval of 2–7 days between the operations is recommended [8, 35]. Operating on both eyes in a single session has the advantage of an optimal rehabilitation of visual acuity with less stress from the anaesthesia and lower costs. However, it is rejected by most surgeons because of the danger of bilateral endophthalmitis. Some authors recommend bilateral occlusion to avoid deprivation between the operations. This procedure is not followed when the operation is carried out within a few days [35], and we also did not perform bilateral occlusion since the operation on the second eye always took place within 3–5 days. If the cataract operation is carried out when deprivation amblyopia with nystagmus is already present, the prognosis with regard to visual acuity is relatively poor. However, an increase in visual acuity to 0.4 and better was occasionally observed after cataract operations in manifest nystagmus [8]. Three children in our patient series had already developed nystagmus. The bilateral lens operation was performed at the age of 8 weeks, 6 months and 3 years respectively to deal with a dense cataract in both eyes. Whereas the nystagmus did not regress at a postoperative visual acuity of 0.16 and 0.2 (preoperative visual acuity of R=L 0.1) in the 3-year-old child, there was a marked decrease in the nystagmus in the two babies. On principle an approach close to the limbus or a pars plana or pars plicata approach can be chosen for the cataract operation in children. In our experience, after making a tunnel incision near to the limbus and after setting up paracenteses it is often necessary to apply a suture to these incisions owing to the relatively high content of elastic fibres in children’s eyes, so that a contact lens cannot be fitted immediately after the operation. It also appears to us that removal of the anterior one third of the vitreous via a pars plana or pars plicata approach is safer

and can be controlled better than via an incision near to the limbus. Ultimately, the decision on the surgical approach is determined by the experience of the surgeon. To date, there has been no controlled prospective study comparing and contrasting the two techniques. In the eye of the mature neonate, the pars plicata of the ciliary body is already almost fully developed, whereas the pars plana is hardly established [1, 7]. Babies born at term have a pars plana with dimensions of 1.6–1.7 mm or 1.87±0.48 mm [14, 18]. In the postnatal phase, the antero-posterior extent of the pars plana increases. However, the concrete growth dynamics of the individual patient cannot be determined exactly. The average values of various morphometric studies serve as a guide. The position of the scleral incision for a retroiridal approach depended on the patient’s age, and we did not observe perioperative complications. In our opinion the pars plana or pars plicata incision is a safe approach for lentectomy. Secondary cataract develops from residual lens epithelia which show overgrowth onto conducting structures (lens capsule, anterior vitreous) [15]. The development of secondary cataract can be definitively prevented only by lentectomy with complete removal of the capsule. However, this radical operation makes it more difficult to carry out the secondary implantation of an IOL which may be necessary later. Complete lentectomy including the posterior capsule is also associated with an increased risk that the patient will develop a retinal detachment as a late complication [22, 25, 30]. The aim of modern lentectomy is to leave in place a capsular ring as an alternative to complete lentectomy. After operation with the method we use it is possible to perform secondary implantation of an IOL into the ciliary sulcus after completion of bulbar growth. However, central posterior capsulotomy and vitrectomy of the anterior one third of the vitreous must be included in the surgical procedure in order to avoid postoperative pupillary block, malignant glaucoma and the overgrowth of regeneratory secondary cataract onto the anterior vitreous interface [12, 24]. In five eyes in our series, secondary cataract developed nevertheless. It had covered the optical axis and could be treated successfully by discission via the pars plana in all eyes. It is also important that the capsulotomy is as central and as circular as possible, since asymmetrical shrinkages can occur owing to the development of secondary cataract, resulting in displacement of the capsulotomy. Development of glaucoma is a frequent complication after operating on a congenital cataract. In the literature, an incidence of 6% [11] to 24% [36] is specified. However, most glaucomas occur only after about 7 years [36]. Asrani and Wilensky [2] specified that postoperative screening investigations are required at intervals of 3 months in the first postoperative year, twice a year in the first 10 years and then once a year. We were unable to discover any signs of glaucoma during a period of

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3 months to 4.5 years (mean 31 months) follow-up observation in our patients. The occurrence of a rhegmatogenous retinal detachment after an operation on cataract in a child is one of the late complications. The average interval between lens operation and retinal detachment is 23–34 years [24, 37]. Seventy-two per cent of the detachments occurred only after more than 10 years [37]. However, the incidence of postoperative retinal detachment after modern surgical techniques can be appraised exactly only after follow-up observation for about 30 years. A further possible complication is the development of cystoid macular oedema. This is rarely observed after

lentectomy. An incidence of 0%–4% is reported [23, 27]. We did not see macular oedema during the follow-up observation in our patients. To summarise, lentectomy via a pars plana or pars plicata approach is a suitable and safe surgical technique for treating cataract in babies and children, if placement of an IOL at the time of cataract removal is not a consideration. Now the Infant Aphakia Treatment Study is being organised and the results of this study will give us new guidelines for identifying correct indications for the use of contact lenses versus IOL implantation in babies and children after surgery for congenital cataract [26].

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