Cataracts in Children, Congenital and Acquired
A cataract is any light scattering opacity of the lens. It is estimated that congenital cataracts are responsible for 5% to 20% of blindness in children worldwide. Incidence varies from country to country. One retrospective study of the prevalence of infantile cataracts in the U.S. showed a rate of 3-4 visually significant cataracts per 10,000 live births. This is a similar rate to a U.K. study which showed 3.18 per 10,000.These numbers underestimate the total number since they do not take into consideration visually insignificant cataracts.
Cataracts may be unilateral or bilateral and can vary widely in size, morphology and degree of opacification from a small white dot on the anterior capsule to total opacification of the lens. Consequently, the effect on vision, course of treatment and prognosis may also be widely variable.
The causes of infantile cataracts have been the source of much speculation and research. Making a distinction between unilateral and bilateral cataracts may be useful when considering etiology.
The majority of bilateral congenital or infantile cataracts not associated with a syndrome have no identifiable cause. Genetic mutation is likely the most common cause. Over fifteen genes involved in cataract formation have been identified, and the inheritance is most often autosomal dominant although it can be X-linked or autosomal recessive. Within the same pedigree, there can be considerable morphologic variation.
Systemic associations include metabolic disorders such as galactosemia, Wilson disease, hypocalcemia and diabetes. Cataracts may be a part of a number of syndromes, the most common being trisomy 21. Intrauterine infections including rubella, herpes simplex, toxoplasmosis, varicella and syphilis are another cause.
In contrast, most unilateral cataracts are not inherited or associated with a systemic disease and are of unknown etiology although they do not rule out the possibility of an associated systemic disease. They are usually the result of local dysgenesis and may be associated with other ocular dysgenesis such as persistent fetal vasculature (PFV), posterior lenticonus or lentiglobus.
Trauma is a known cause of pediatric cataracts. If there is no known history of trauma to explain an acquired cataract in this age group, investigation must be considered in children who present with other signs suggestive of child abuse.
Regardless of the etiology, prompt treatment of visually significant cataracts is necessary to allow proper development of vision.
In many cases of congenital cataracts, there is a family history. History of prenatal and pregnancy history can also provide clues.
Cataracts present as an opacity in the lens which run a spectrum from easily visible in the undilated state and apparent to the parents or pediatrician, to much more subtle changes requiring dilation and careful examination with a slit lamp. The red reflex is an extremely useful part of the exam giving an estimate of size and location within the visual axis, even in an uncooperative child.
Cataracts are classified according to their morphological appearance and location; however, making the diagnosis of a specific type of cataract can be difficult if it spreads to involve multiple layers, obscuring the original opacity.
Cataracts may be a part of another disease or syndrome, and are sometimes the initial finding that leads to the diagnosis. A cataract may be accompanied by additional noticeable ocular abnormalities such as microcornea, megalocornea, coloboma of the iris, aniridia, and zonular dehiscence.
Often an infant with mild cataracts appears asymptomatic, delaying the diagnosis for years. At other times, lack of reaction to light, strabismus, a failure to notice toys and faces or an apparent delay in development become the cause of concern. Mild cataracts may cause photophobia only in bright lights. Dense cataracts also may be discovered if they lead to the development of sensory nystagmus.
For unilateral cataracts in an otherwise healthy child, an extensive workup is not necessary. The most critical part of the workup is a thorough ophthalmologic exam including slit lamp examination of both eyes, checking intraocular pressure, and an ultrasound of the posterior pole if not visible. If the exam reveals the classic appearance of a specific diagnosis such as persistent fetal vasculature (PFV) or posterior lenticonus, no further evaluation is necessary.
The first step in the workup of bilateral cataracts should be a family history including examination of family members. If there is a clear autosomal dominant pattern and the child is healthy, further evaluation is not necessary. In cases without clear family history, a thorough pediatric and developmental exam should be performed. Recommended lab workup includes TORCH titers, VDRL, serum calcium and phosphorus levels and urine for reducing substance. Additional systemic workup should be done in coordination with the pediatrician. Dysmorphic features may suggest the need for involvement of a geneticist.
For bilateral cataracts without a family history, the recommended workup includes a urine test for reducing sugars, TORCH (toxoplasmosis, rubella, cytomegalovirus, varicella) screening, a Venereal Disease Research Laboratory (VDRL) test for syphilis, and a blood test for calcium, phosphorus, glucose, and galactokinase levels. Dysmorphic features may suggest the need for involvement of a geneticist.
The differential diagnosis for leukocoria or white pupil includes retinoblastoma, PFV, retinopathy of prematurity, chorioretinal colobomas, toxocariasis, Coats disease, vitreous hemorrhage and other retinal tumors. These can be distinguished by a complete exam of the anterior and posterior segment, often including ultrasound.
Not all pediatric cataracts require surgery. A small, partial or paracentral cataract can be managed by observation. Pharmacologic pupillary dilation with phenylephrine or tropicamide can be helpful. Dilation with atropine should be avoided as it is amblyogenic due to the cycloplegia. Part-time occlusion may be necessary in unilateral or asymmetric cases that develop or are at risk for amblyopia. These techniques may at least delay the need for surgery until a point when eye growth has stabilized and an IOL can be implanted with less refractive uncertainty. Because of the unpredictability in the progression of partial cataracts, these patients should be carefully monitored and if significant amblyopia develops and is unresponsive to treatment, surgical intervention should be performed.
Considerations for treatment
Decision about surgery depends upon age of patient at presentation, extent of opacity and associated conditions.
If child is <1 year of age, the surgical approach is typically lensectomy pars plana or limbal leaving anterior capsular rim (for a secondary IOL at a later point), optic rehabilitation using aphakic glasses or contact lenses and amblyopia and strabismus management. In older children, a lensectomy with primary posterior capsulotomy and anterior vitrectomy and potentially a lens implant can be considered. Management always includes amblyopia management and careful refractions for bifocals (even with IOL implantation). In children older than 5-7, a posterior capsulotomy may not be necessary if they are able to sit at the slit lamp for a Yag laser.
If the cataract(s) are felt to be visually significant, surgical intervention is the only option. The timing of surgery is critical for visual development. Most investigators recommend surgery within the first two months of life. Surgery is typically at 4-6 weeks of age for unilateral cataracts and before 3 months for bilateral cataracts. There has been evidence to suggest that before one month of age, the risk of aphakic glaucoma is increased.  In cases of bilateral cataracts, it may be advantageous to perform surgery on both eyes in the same intervention to allow for simultaneous initiation of visual rehabilitation as well as reducing exposure to general anesthesia. In this setting, treating each eye as a separate sterile procedure may reduce infection risk.
Removal of the lens can be approached through the limbus or the pars plana. The limbal approach has the advantage of maintaining the posterior capsule to facilitate posterior chamber intraocular lens (IOL) implantation if desired.
Several options exist to open the anterior capsule in pediatric cataracts. The ideal anterior capsulectomy technique is one that results in low incidence of radial tears and is easily performed. In cases of dense cataract, dye can be used to stain the anterior capsule, making this step easier and safer. A manual continuous curvilinear capsulorhexis (CCC), which is the preferred method in adult eyes, can be difficult in pediatric cases due to the elasticity of the pediatric capsule. However, when it can be controlled and completed, it creates an edge, which has a low incidence of radial tears.  A 23 G vitreous end gripping forceps using push pull technique is very effective.
A mechanized circular anterior capsulectomy, known as vitrectorhexis has been proven to be a very good, safe alternative if the CCC is not possible. The vitrector tip is placed through a stab incision at the limbus and irrigation is provided though a sleeve around the vitrector or though a separate limbal incision. The vitrector port is oriented posteriorly, and held in the center of the capsule to create an initial opening. The opening is enlarged in a circular fashion, holding the cutter just anterior to the capsule to aspirate the capsule up into the cutter. A smooth, round capsulectomy that is also resistant to radial tears can be produced.
Pediatric cataracts are soft and therefore phacoemusification is not needed. The lens cortex and nucleus can be removed with an irrigation-aspiration or vitrector hand piece.
To reduce the risk of posterior capsule opacification most surgeons perform a posterior capsulorhexis at the time of surgery. The lens capsule can be filled with viscoelastic and a posterior continuous capsulorhexis made slightly smaller than the anterior one. If an IOL is to be implanted, it can be placed in the capsular bag at this time and some advocate the technique of optic capture where the optic is pressed through the posterior capsulorhexis and the haptics remain in the bag. 
An anterior vitrectomy can be performed either though the limbal incisions, after making the posterior capsulotomy with the vitrector hand piece, or through the pars plana. The anterior vitreous is removed and the lens epithelial cells therefore cannot grow in the vitreous face.
The Infant Aphakia Treatment Study randomized children 1-7 months of age with a unilateral cataract to primary IOL implantation vs aphakia. There was no significant difference between visual acuity of operated eyes in children who underwent primary IOL implantation and those left aphakic. However, there were significantly more adverse events and additional intraoperative procedures in the IOL group.
The refractive goal of cataract surgery in children is complicated and involves many factors. Most surgeons will chose to make the child hyperopic (as to avoid high myopia in adulthood) but there is currently no agreed upon standard. Aphakic and pseudophakic children will need bifocal glasses for the rest of their lives.
A pars plana approach can be used when no IOL implantation is intended. An attempt is made to remove the whole cataract and the adjacent vitreous with a vitreous cutter.
Care should be taken to remove the viscoelastic entirely to prevent elevated intraocular pressure following surgery and the anterior chamber should be checked carefully for vitreous. The sclera in children is soft and elastic and it is difficult to achieve a self-sealing incision, thus the incision should be closed using 10-0 nylon or Vicryl suture.
Opacification of the visual axis is the most common complication of cataract surgery in children. This is a serious complication because it can lead to amblyopia. A posterior capsulorhexis and anterior vitrectomy as previously discussed is one way to avoid this. An IOL can prevent the formation of a Sommering’s ring, but it is also easier for the lens epithelial cells to migrate to the center of the pupil. Others have suggested captruring the optic by placing the haptics in the bag and pushing the optic through the posterior capsularhexis may prevent opacification. If opacification occurs, a Nd:YAG laser capsulotomy can be attempted. In this age group, general anesthesia is necessary and a surgical membranectomy may be indicated if the Nd:YAG laser is not effective or available.
Secondary glaucoma is the most sight threatening complication of pediatric cataract surgery. Approximately 20% of children will develop glaucoma following cataract surgery. Open-angle glaucoma can develop months to years after the surgery. The two most significant risk factors for development of glaucoma following pediatric cataract surgery are young age of surgery and microphthalmia. Angle-closure glaucoma can result from anterior synechiae leading to pupillary block, which can be treated with a peripheral iridectomy. Some eyes with secondary glaucoma can be controlled with topical medication, but many cases will require additional surgical intervention. Children who have had cataract surgery require lifelong monitoring for the development of glaucoma.
Fibrinous or exudative postoperative uveitis is common due to increased tissue reactivity of these eyes. Inflammation can be treated with topical steroids. The visual axis may require clearing with the Nd:YAG laser or vitrectomy/membranectomy. Tissue plasminogen activator has been recommended in cases of severe fibrin deposition on the IOL surface, threatening visual rehabilitation.
Endophalmitis is a rare but serious complication. It occurs with approximately the same frequency as adult cataract patients. Common organisms are Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus viridans.
The lifetime risk of retinal detachment after cataract surgery in pediatric patients is increased. Risk factors for retinal detachment are high myopia and repeated surgeries.
Careful surgical technique can reduce early postoperative complications such as wound leak, iris to the wound and vitreous to the wound. Retinal hemorrhages can occur, probably as a result of leaving the intraocular pressure low at the end of surgery. Iris capture of the IOL optic can cause discomfort and disfigure the pupil. This is caused by iris scarring to the posterior capsule and risk can be reduced by careful placement of the lens at the time of surgery. Cystoid macular edema in children is not common as with adults, but can be seen on rare occasions.
Amblyopia, strabismus and nystagmus which may have developed prior to cataract surgery may continue despite removal of the cataract(s) and must also be addressed.
In the postoperative period, it is important to prevent and keep under check any significant inflammatory reaction. The prolonged use of local steroids, nonsteroidal anti-inflammatory agents, and atropine are recommended for this purpose. Systemic steroids are used by some to prevent or treat secondary membranes, but often are not successful resulting in the need for Nd:YAG laser or surgery. The eye must be monitored regularly for the development of a secondary cataract or any other early or delayed problem.
Unlike adult cataract, the management of a pediatric patient is not complete when the post-operative period is over. In some ways, the more difficult and important part of management is still ahead. Neglecting the treatment and prevention of amblyopia or not giving proper refractive correction is leaving the work half done. Lifelong careful follow-up is essential for all pediatric cataract cases.
Management of pediatric aphakia depends on the age of the child, the family situation and whether there are abnormalities of other ocular structures such as the cornea and the development of the child. For infants, aphakic contact lenses are the treatment of choice for those infants who do not receive an IOL.
Although not the first choice, aphakic spectacles are an option in children who are contact lens intolerant or as a backup to contact lenses in bilateral aphakes. Spectacles should not be used for unilateral aphakes because they disrupt binocular fusion. However, for a child without binocular potential or strabismus, unilateral aphakic spectacles in combination with patching can be used. A high refractive index lens can diminish the weight and size of aphakic spectacles making them better tolerated.
Amblyopia treatment must be initiated as soon as possible. For amblyopia treatment to be effective, the amblyopic eye must have not only a clear visual axis, but also the proper corrective lenses to provide the retina with a clear image. In unilateral cases, the amount of patching required depends on the age at which the visual axis was cleared Patient and family education about amblyopia and treatment strategies is essential.
The course and prognosis of pediatric cataracts is highly variable. The likelihood and rate of progression is very difficult to predict. In addition, the presence of other ocular or systemic abnormalities contribute to the variable outcome.
The most serious complication of congenital cataracts is permanent visual impairment. When the visual axis is blocked by a lens opacity during the sensitive period of visual development, irreversible amblyopia and permanent nystagmus may result. The first two months of life are the most critical for visual development; amblyopia resulting from visual deprivation after the age of 2 to 3 months can often be reversible to some degree. Visual development continues until at least 7 years of age.
Unilateral cataracts carry a less favorable prognosis than bilateral cataracts. Even a minimal opacity can create significant amblyopia. A child with a unilateral cataract is also at greater risk for anisometropia, which can complicate the picture.
In addition to clearing the visual axis by appropriate surgical technique, proper optical correction in the form of aphakic glasses, contact lenses or intraocular lens implants is essential for good visual development. This requires an ongoing commitment from both the ophthalmologist and family of the infant.
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