|Year : 2012 | Volume
| Issue : 3 | Page : 115-121
Management of congenital cataract
Department of Surgery, College of Medicine, Taif University, Taif, Saudi Arabia
|Date of Web Publication||15-Jan-2013|
Department of Surgery, College of Medicine, Taif University, PO Box 888, Taif-21974
Source of Support: None, Conflict of Interest: None
Cataracts are opacities of the crystalline lens. Because they frequently interfere with normal visual development, they represent an important problem in pediatric ophthalmology. Despite dramatic improvement in the treatment of pediatric cataract, it continues to be a major cause of decreased vision and blindness in children. By far, the most common cause of poor visual results after surgery is irreversible amblyopia.
Keywords: Amblyopia, cataract, congenital
|How to cite this article:|
Althomali T. Management of congenital cataract. Saudi J Health Sci 2012;1:115-21
| Etiology|| |
The etiology of congenital cataracts can be established in many children by careful preoperative assessment. The most common etiologies include intrauterine infections, metabolic disorders and genetically transmitted syndromes [Table 1]. In an otherwise healthy child, an extensive preoperative evaluation is not usually necessary. A pediatrician and an ophthalmologist working together can detect most of the associated ocular and systemic diseases with only few simple urine and blood tests in addition to family history, history of systemic disorders, associated ocular abnormalities and, most importantly, whether the cataract is bilateral or unilateral [Table 2].
| Surgical Management of Pediatric Cataract|| |
Choyce  implanted the first anterior chamber intraocular lens in a child for correction of uniocular aphakia in 1955. Subsequently, Bikhorst and Gobin  implanted an iris clip IOL in a child and noted that nystagmus did not preclude a marked improvement in visual acuity in children. They also noted that, in some children, amblyopia treatment was easier with IOL implantation than with contact lens rehabilitation of aphakic eyes. The recent advances of IOL technology and improved microsurgical techniques for managing the lens capsule offers pediatric cataract surgeons the ability to safely perform in-the-bag IOL placement combined with pars plana capsulotomy and anterior vitrectomy.
| Estimation of Intraocular Lens Power|| |
Historically, there were two ways of estimating IOL power in a child. Hiles implanted a standard adult power 19 diopter IOL.  In 66% of the cases, this required spectacle overcorrection of residual sphere and/or cylinder. As David Taylor has remarked in an editorial in the British Journal of Ophthalmology in 1988,  it is possibly unreasonable to remove a cataract in an infant to find that after implanting a standard adult power IOL, a large overcorrection is required to achieve emmetropia. Ben-ezra and Aron-Rosa and others have taken the approach of correcting the child for emmetropia at the time of surgery. , However, in very young infants, this would almost certainly lead to large degrees of overcorrection when the child reaches adulthood.
It was not until Gordon and Donzis  investigated the growth potential of 148 eyes of 79 patients in Tulane University Hospital that the growth pattern of the globe was accurately elucidated. They reviewed cases of 23 premature and full-term newborn infants. Nineteen patients between 2 months and 6 years and 37 patients between 5 and 36 years of age were also included. All patients underwent axial refractive cyclopegic retinoscopy, keratrometric measurement and axial length determination using applanation A-scan ultrasonography. The author used a modification of the Sanders-Retzlaff-Kraff (SRK) formula to determine IOL power. The SRK formula treats the human lens as if it were a posterior chamber IOL. In the standard SRK formula, a 1 mm change in axial length corresponds to a 2.5 diopter change in lens power, regardless of axial length. Gordon and Donzis assumed that a 4.25% change in axial length corresponded to a 2.5 diopter change in refractive power. They felt that this modification was more accurate in the very short eye, because a 1 mm reduction in axial length in a short eye represents a much larger percentage of decrease in axial length than in a larger adult eye. The measurements of axial length demonstrated very large changes between birth and adulthood. At birth, the axial length is approximately 15 mm. This increases rapidly to reach approximately 23 mm. Similarly, keratometric measurements showed marked changes in the first few months of life. A large degree of corneal flattening occurred between 2 months of prematurity and 24 months of age, the keratometry at birth being approximately 51 diopters compared with 44.1 diopters at 2 years of age. Finally, adult keratometric measurements are approximately 43.5 diopter lens to correct to emmetropia. A child of 2 years would require a 26 diopter IOL and an adult between 20 and 36 years of age would require an 18.8 diopter IOL to correct to emmetropia. This shows an almost 25 prism diopter difference between the 30-35 week age group and the adult age group. This difference is a result of an 8 mm increase in axial length. The findings of Gordon and Donzis show that the greatest changes in keratometry and axial length occur prior to 2 years of age. From 2 years of age to adulthood, one can expect a 5-6 diopter shift toward myopia.
Rather than implanting a standard adult IOL power, or implanting to correct to emmetropia in the infant age group, Gordon and Donzis suggest that in a 6-month child, for example, an IOL of 23-24 diopters could be implanted. This would require a spectacle or contact lens overcorrection in the first postoperative year. However, at the age of 2, 3 and 4 years, the child would be emmetropic. They point out that this is the age in which contact lens intolerance occurs. After this stage, some degree of contact lens or spectacle overcorrection might be required. Another approach is simply not to implant IOLs in any children under the age of 2 years. Buckley suggest that a 2-year-old child could be expected to have a myopic shift of approximately 5-6 diopters.  He recommend an undercorrection in these children by no more than 3 diopters. Any greater undercorrection would lead to anisometropia, and would conflict with amblyopia treatment. Buckley suggested that there will certainly be residual myopia in adulthood that can easily be treated by contact lenses or spectacles or use of the excimer laser.
| Management of the Anterior Lens Capsule in Pediatric Cataract Surgery|| |
The anterior continuous curvilinear capsulorhexis is a critical surgical step of modern cataract extraction and IOL implantation surgery. The can-opener capsulotomy, used in large-incision extracapsular cataract extraction, is prone to the occurrence of radial tears. This procedure can lead to unwanted surgical complications, including vitreous loss.  A continuous curvilinear capsulorhexis is smoother and much more resistant to radial tears during cataract surgery.  The integrity of the anterior capsular opening (capsulectomy with capsulotomy) is critical not only for reducing intraoperative complications, such as vitreous loss, but also for the long-term, stable centration of IOLs. ,, Therefore, the continuous curvilinear capsulorhexis has become the gold standard procedure in the management of cataracts for both adults and children. ,
In the treatment of young children, manual continuous curvilinear capsulorhexis is difficult to perform and requires good surgical skill because the lens capsule is highly elastic and more force is necessary for it to be torn.  The incidences of the radial tears of the lens capsule  and extension of the tears to the lens equator are proportional to the force used in generating the capsulorhexis.  Therefore, the large amount of force required in pediatric manual continuous curvilinear capsulorhexis increases the incidence of radial tears significantly in young eyes.
There are different ways to minimize the difficulty of manual anterior continuous curvilinear capsulorhexis in pediatric eyes, including high magnification under the operative microscope, using more viscoelastics, to vector the force more toward the center of the pupil, 1-2 mm smaller capsular tear than the target size, grasping the capsular flap more frequently during the procedure and capsular staining with indocyanine green. Various surgical approaches have been studied. Wilson et al. reported anterior vitrectorhexis (mechanized capsulectomy) as an alternative approach.  They compared mechanized capsulectomy with manual continuous curvilinear capsulorhexis using 18 pairs of postmortem pediatric eyes. They concluded that mechanized capsulectomy provides surgeons with an alternative for pediatric eyes in which standard continuous curvilinear capsulorhexis may be difficult to perform.  They also applied the anterior vitrectorhexis technique to 20 pediatric eyes. Radial tears of the anterior lens capsule occurred in 15% of the eyes. 
Radiofrequency diathermy anterior capsulectomy has been studied as an alternative technique for mature cataracts. ,, Comer et al. later reported radiofrequency diathermy anterior capsulectomy in 14 pediatric eyes with good results. Radiofrequency diathermy may have advantages over manual continuous curvilinear capsulorhexis in mature cataracts or in eyes with small pupils. , Disadvantages of this technique include common longitudinal tears of the capsulorhexis edge and increased vulnerability to radial tears during surgical manipulation. 
Indocyanine green staining of the anterior capsule was first described by Horiguchi et al. This technique was reported to facilitate the performance of circular continuous capsulorhexis in eyes with mature cataracts. Guo et al. have reported that capsulorhexis enhanced by indocyanine green staining in pediatric cataract and IOL surgery have produced excellent and consistent results. 
| Management of Posterior Lense Capsule and Anterior Vitrectomy|| |
Posterior capsule opacification occurs frequently after cataract extraction in children; in some cases, it develops soon after surgery.  In younger children, primary clouding of the visual axis occurs at a critical period in their visual development, and the major concern is amblyopia, especially in cases of monocular cataract. A clear visual axis and amblyopia therapy are necessary to achieve visual rehabilitation. Surgical removal of the posterior capsule and anterior vitreous have been considered the "gold standard" in pediatric cataract surgery, especially in patients younger than 5 years old.  The anterior vitreous face serves as the scaffold across which the lens epithelial cells migrates and transform into fibroblasts causing intense epithelial regrowth.
Some surgeons recommend leaving the posterior capsule intact even in very young children and performing neodymium:YAG laser capsulotomy later, if necessary. However, the capsule can become excessively thick in these patients, and often requires greater laser energy to open the visual axis. This high energy can cause potential complications, including IOL damage, raised intraocular pressure and retinal detachment. Furthermore, the opening after neodymium:YAG laser capsulotomy may close, requiring repeated laser treatments. Alternatively, the postoperative membrane or reopacified posterior capsule can be surgically removed with pars plana membranectomy.
The incidence of posterior capsule opacification is much higher in pediatric patients than in adults. Posterior capsule opacification has been reported to range from 44% to 100% in pediatric patients. ,,, Sharma et al.  revised 39 pediatric eyes, in which cataract extraction and IOL implantation were performed with intact posterior capsules. Posterior capsule opacification occurred in 87.2% of these patients. A total of 74.3% of the eyes needed treatment for posterior capsule opacification, including neodymium:YAG laser capsulotomy in 19 eyes (48.7%) and surgical membranectomy in 10 eyes (25.6%).
Plager et al. reported 79 pediatric eyes with cataract.  Of 71 eyes in which the posterior capsule was left intact, 90% developed posterior capsule opacification by 3.5 years after surgery and 42% (30 of 71) required a posterior capsulectomy at an average of 2 years after surgery. The authors found that the incidence of posterior capsule opacification begins to rise rapidly at 18 months after surgery. The average time for development of visually significant posterior capsule opacification was 2 years after surgery. The authors concluded that primary posterior capsulectomy with anterior vitrectomy should be considered at the time of lens implantation in children who are not expected to be candidates for neodymium:YAG capsulotomy within 18 months of surgery. 
A primary posterior capsulectomy has been reported to play an important role in the delay of posterior capsule opacification in children. A posterior capsular opening can be performed using various approaches, including posterior continuous curvilinear capsulorhexis,  vitreous-cutting devices ,, and radiofrequency diathermy capsulotomy. ,
Manual primary posterior continuous curvilinear capsulorhexis has been studied in pediatric cataract surgery. , The advantages of posterior continuous curvilinear capsulorhexis are that it (1) provides a much stronger margin that is resistant to the peripheral extension of radial tears, (2) holds the vitreous in place better when vitrectomy is needed, (3) better centers and fixes the IOL in the capsular bag and (4) makes optic capture possible. , One of the major disadvantages of posterior continuous curvilinear capsulorhexis is that it poses a technical challenge. Er et al. performed a posterior continuous curvilinear capsulorhexis without vitrectomy on 26 eyes with congenital cataracts. The visual axis remained clear in all of these eyes, with an average follow-up of 10 months.  Zetterstrom et al. reported posterior capsule opacification in only one of 21 pediatric eyes after posterior continuous curvilinear capsulorhexis without vitrectomy.  Vasavada and Desai reported different results. In their study, 62.5% (five of eight) of the eyes that underwent posterior continuous curvilinear capsulorhexis without vitrectomy required secondary pars plana vitrectomy. 
Vitrectomy posterior capsulotomy has also been used in children with cataracts. , Parks described this technique of removing all but 2 mm of the peripheral posterior lens capsule with a vitreous cutter.  Caputo et al. also reported primary posterior capasulectomy with vitrectomy using the vitrector of the SITE device (Johnson & Johnson and IOLAB, Horsham, PA, USA) in 64 pediatric eyes with good outcome.  BenEzra and Cohen reported a primary posterior capsulectomy and anterior vitrectomy using the Outcome device (Cooper Medical Devices Corp., San Leandro, CA, USA).  Plager et al. recommended that when visibility, capsule toughness and elasticity preclude the possibility of an adequate posterior continuous curvilinear capsulorhexis, a posterior capsulectomy should be made with a mechanical vitreous cutting device. 
Radiofrequency diathermy posterior capsulotomy has also been reported in cataract surgery. , Radiofrequency endodiathermy was first described by Kloti in 1984.  The technique was first reported to create both primary anterior and posterior capsulotomy using diathermy in 14 pediatric eyes without anterior vitrectomy. Neither capsular tears nor posterior capsule opacification was noted in these eyes with 7-16 months of postoperative follow-up. Fenton and O'Keefe performed a posterior capsulotomy using radiofrequency diathermy without anterior vitrectomy in 32 pediatric eyes with cataracts. IOLs were inserted in 20 of these eyes. The mean follow-up was 19 months. The incidence of posterior capsule opacification requiring laser capsulotomy was 15.6% in this series. Fenton and O'Keefe concluded that primary posterior capsulotomy without anterior vitrectomy is a safe and effective procedure with a low rate of posterior capsule opacification. It is recognized that the capsulotomy edge produced by manual continuous curvilinear capsulorhexis is significantly stronger than that produced by radiofrequency diathermy. The disadvantage of the latter technique is reduced capsule tension strength and increased vulnerability to surgical manipulation. 
The important role of primary posterior capsulotomy and anterior vitrectomy during pediatric cataract surgery was reported by Parks  In 1983 and subsequently analyzed in other studies. The reported rates of reopacification of the visual axis after posterior capsulotomy and anterior vitrectomy are variable depending on the age of the patient at the time of surgery. However, these rates are significantly higher if the posterior capsulotomy is not combined with an anterior vitrectomy. , BenEzra and Cohen  evaluated the role of posterior capsulotomy in a large series of pediatric cataracts. They reported that all undergoing primary capsulotomy combined with anterior vitrectomy did not need additional surgeries, whereas all eyes in which the posterior capsule was left intact had to undergo one or more secondary interventions. 
Thus, in summary, primary postcapsulotomy with anterior vitrectomy is a safe and effective method of managing the posterior capsule in pediatric cataract with IOL implantation. Visual axis reopacification is associated with a very young age at the time of surgery. , The size of posterior capsulotomy has also been noted as an important factor in reducing posterior capsule opacification. , It has been emphasized that removal of all but 2 mm of peripheral posterior lens capsule with anterior vitrectomy eliminates the need for secondary surgery. Anterior vitrectomy is the best method for avoiding the development of amblyopia resulting from gradual posterior lens capsule opacification. 
The reported disadvantages of posterior capsulotomy and anterior vitrectomy include dislocation of IOL  and cystoid macular edema,  but the risk is minimal in children. ,,
Anterior vitrectomy is associated with the risk of vitreous incarceration to surgical wounds, which increases the risk of retinal tears and detachment. ,
| Lens Type|| |
With the advent of manual primary posterior continuous curvilinear capsulorhexis, capsular bag fixation of the IOL has become more prominent in pediatric cataract surgery. The incidence of chronically inflamed eyes with pupillary capture is low if the IOL is in the bag and a manual primary posterior continuous curvilinear capsulorhexis is created. These techniques also facilitate primary capsulotomy and anterior vitrectomy after IOL implantation. In addition, a complete manual primary posterior continuous curvilinear capsulorhexis is mandatory if the surgeon is contemplating using a recent innovation such as capsulorhexis capture or posterior continuous curvilinear capsulorhexis capture of the IOL optic. ,
Use of acrylic IOLs has been associated with a decrease in the incidence of posterior capsular opacity (PCO) in adults.  Capsular bag implantation of acrylic IOLs with a square edge enhanced the barrier effect. It has been shown that optics with a round edge might allow some cells to migrate under the tapered edge of the optic onto the posterior capsule. A truncated optic edge appears to create an abrupt and effective barrier to these cells. , Another factor that appears to play a role in preventing PCO is the stickiness of the IOL biomaterial, which might create adhesion between the capsule and the IOL optic. , However, the high activity level of lens epithelial cells in children and the greater postoperative inflammation than in adults may negate some advantages of acrylic IOLs with a square edge in the pediatric population.
A recent study by O'Keefe and coauthors  found no correlation between PCO and IOL material in the 26 eyes of 13 children. Wilson et al. report a similar postoperative neodymium:YAG capsulotomy rate between implantation of para-Methoxy-N-methylamphetamine (PMMA) IOLs (50%) and AcrySof IOLs (45%) in eyes with an intact posterior capsule.
Ram et al. observed no difference in the incidence of PCO between the hydrophobic acrylic IOL with truncated edges and the PMMA IOL. One difference was that eyes with acrylic IOLs developed PCO 6-8 months after primary surgery and those with PMMA lenses developed PCO approximately 3 months after primary surgery. This delay in visual axis opacification allowed more time for amblyopia management by occlusion therapy. 
Stager and coauthors  evaluated 26 eyes with an intact posterior capsule and acrylic IOL. The mean time from surgery to development of PCO was 8 months. However, Wilson et al. found no difference in the surgery-PCO interval between acrylic and PMMA IOLs (18.6 months and 18.3 months, respectively).
| What is the Youngest Age at Which IOL Can Be Implanted?|| |
Implantation of posterior chamber IOL at the time of cataract surgery in children has become common practice. Good to excellent visual results with very low complication rates have been reported in numerous series. ,, The vast majority of children in these studies were older than 2 years of age at the time of surgery, but recent reports have included some infants. ,,, Some data reporting complications after IOL surgery in infancy have been published. The first report from a pilot study of pooled data from five institutions for the Infant Aphakia Treatment Study (IATS) project described a high rate of complications requiring reoperations (eight of 11, 73%). Soon after surgery, in a group of infants undergoing IOL implantation,  there have been several other sporadic reports that include IOL in infants a few babies. ,,
David et al. reported the complications occurring in the first year following surgery in a series of 15 consecutive eyes of 13 infants under 6 months of age undergoing surgery at one center. He found that 12 of the 15 eyes (80%) developed secondary opacification across the visual axis posterior to the IOL requiring a second Pars Plana Vitrectomy (PPV) and one eye developed pseudophakic glaucoma. Two patients required a third PPV to keep the visual axis clear.  The retrolental opacification appears to be done to an aggressive proliferation and migration of lens, especially epithelial cells across the posterior surface of IOL. We noticed that eight of 15 patients had Persistent Hyperplasic Primary Vitreous (PHPV), which was associated with more complications and difficult surgery.
Until we find a surgical technique, IOL style or material or postoperative medication to effectively prevent aggressive opacification of the visual axis, it may be prudent to caution families preoperatively about the likelihood of the need for a second surgery after initial lensectomy/IOL/vitrectomy in pediatric patients less than 6 months.
| Our Experience in Pediatric Cataract Management|| |
A continuous curvilinear capsulorhexis of the anterior capsule with a foldable acrylic IOL and primary posterior capsulotomy with anterior vitrectomy is preferable in children above 6 months and below 6 years, whereas lensectomy with foldable IOL without posterior capsulotomy is the preferred approach for pediatric patients older than 6 year or for those who would cooperate for YAG laser capsulotomy at a later time. The posterior capsule was left intact in older children (older than 6 year) or in those who cooperate for laser treatment when indicated. IOL insertion in pediatric patients below 6 months can be done for unilateral cataract and in patients with a high risk of amblyopia after surgery due to expected poor family compliance with ambyopia management.
| Patient Selection|| |
Patients in whom a lensectomy is performed must be fully informed of the possible outcomes. Many parents do not understand that a lens is vital for visual function. They may not understand that amblyopia is present and may feel that once the cataract is removed, the child will see normally again. Parents must be instructed that once the cataract is removed, the child will need a contact lens or IOL in order to compensate for the loss of the physiological crystalline lens function. They then need to be informed that tight amblyopia treatment is essential to the final outcome. This may require spectacle overcorrection and occlusion regiments for many years. Parents should be encouraged to help the physician to come to a decision as to how the individual child's aphakia should best be corrected. It may be a truism that compliant patients will do well with either a contact lens or IOL, but those who are likely to be noncompliant with a contact lens should consider the use of IOL. Patients presenting with late congenital cataracts should be informed that visual results are likely to be poor after lens removal and aphakic correction, but that some degree of improvement may be possible.
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[Table 1], [Table 2]