A cataract is an opacification of the crystalline lens. Congenital or infantile cataracts are present within the first year of life.[1] Timely diagnosis relies on pediatrician screening exams. If a visually significant cataract goes undetected in an infant, permanent visual loss may ensue.[2]
Not all cataracts are visually significant. If a lenticular opacity is in the visual axis, it is considered visually significant and may lead to blindness. If the cataract is small, in the anterior portion of the lens, or in the periphery, there may be no effect on vision.
Unilateral cataracts usually are the result of isolated, sporadic incidents. They can be associated with ocular developmental abnormalities (eg, posterior lenticonus, persistent fetal vasculature, anterior segment dysgenesis, posterior pole tumors).
Bilateral cataracts may be inherited or associated with systemic disease. Therefore, a systemic work up with genetic, metabolic, and infectious testing may be considered. Associated diseases include chromosomal trisomies (eg, Down, Edward, and Patau syndromes), metabolic conditions (eg, diabetes, hypoglycemia, and galactosemia), Lowe syndrome, and congenital infections (eg, toxoplasmosis, rubella, cytomegalovirus, and herpes simplex [TORCH]). Most unilateral cases and approximately half of all bilateral cases are idiopathic.[3]
The lens forms during the invagination of surface ectoderm overlying the optic vesicle. The embryonic nucleus develops by the sixth week of gestation. Surrounding the embryonic nucleus is the fetal nucleus. At birth, the embryonic and fetal nuclei make up most of the lens. Postnatally, cortical lens fibers are laid down from the conversion of anterior lens epithelium into cortical lens fibers.
Any insult (eg, metabolic, infectious, traumatic) to the nuclear or lenticular fibers may result in an opacity of the clear lenticular media. The location and pattern of this opacification may be used to determine the timing of the insult as well as the etiology.
In 2019, Shiels and Hejtmancik wrote that a cataract typically "is caused by the presence of high-molecular-weight (HMW) protein aggregates or disruption of the lens microarchitecture. In general, genes involved in inherited cataracts reflect important processes and pathways in the lens including lens crystallins, connexins, growth factors, membrane proteins, intermediate filament proteins, and chaperones."[4]
United States
The prevalence of congenital cataracts in the United States has been reported to be 1.2-6.0 cases per 10,000.[5]
International
The worldwide incidence of congenital cataracts is unknown and likely underestimated in underdeveloped countries. It has been reported that there are approximately 20,000-40,000 cases of children born with congenital or childhood cataracts per year.[6]
Congenital or infantile cataracts are present within the first year of life. However, timely diagnosis depends on appropriate access to medical care and pediatrician screenings.
A 2020 review of the genetics of congenital cataracts found that genetic defects are responsible for approximately one fourth of congenital cataracts. Multiple mutations have been identified in upwards of 100 genes associated with congenital cataracts.[7]
Visual morbidity may result from deprivation amblyopia, refractive amblyopia, nystagmus, strabismus, glaucoma, and retinal detachment.
Visually significant congenital cataracts result in deprivation amblyopia, which limits visual acuity. To limit the severity of deprivation amblyopia, it is recommended that unilateral congenital cataracts be removed by 6 weeks of age and bilateral congenital cataracts be removed by 10 weeks of age.[3] Timely diagnosis and surgical intervention followed by management of amblyopia is very important for improving visual outcome.[8] Depending on patient age at the time of surgical intervention, infants are often left aphakic (without an intraocular lens). Management of amblyopia requires a combination of patching and correction of refractive error either with a contact lens or aphakic glasses. In addition, patients who have had surgery for congenital cataracts require lifelong monitoring due to risk for developing complications such as posterior capsule opacification, strabismus, glaucoma, and retinal detachment.[6]
Removal of the cataract is only the beginning. Visual rehabilitation requires many years of refractive correction (with contact lenses or aphakic glasses), possible patching for amblyopia, possible strabismus surgery, and glaucoma screenings. Patients’ parents must be made aware of the risk for potential visual loss from amblyopia, glaucoma, and retinal detachment. Repeated surgical procedures, including a secondary lens implant if other modalities of refractive correction fail, may be needed. If the etiology is determined to be genetic, genetic counseling can be considered and all future offspring should have an ophthalmologic exam.
For excellent patient education resources, visit eMedicineHealth's Eye and Vision Center. Also, see eMedicineHealth's patient education article Cataracts.
Congenital cataracts are present at birth but may not be identified until later in life. Patients may be referred by the pediatrician for an abnormal or absent red reflex. It is important to obtain a full prenatal and birth history. It also is important to ask about past medical history including developmental milestones and other systemic findings such as seizures or neurologic abnormalities. Family history including history of childhood cataracts should be investigated. Finally, depending on the patient’s age, questions about visual behavior can be useful. By age 3 months, patients should begin to track with each eye, and the eyes should be straight in alignment. If there is a delay in the diagnosis of a cataract, the patient may develop strabismus or nystagmus prior to presentation.
Unilateral congenital cataracts are usually idiopathic and the result of isolated, sporadic incidents. They can be associated with other ipsilateral ocular developmental abnormalities (eg, posterior lenticonus, persistent fetal vasculature, anterior segment dysgenesis, posterior pole tumors). These cataracts do not require a systemic work up.
Bilateral cataracts may be idiopathic, inherited, or associated with systemic disease. Therefore, a systemic work up with genetic, metabolic, and infectious testing may be considered. Associated diseases include chromosomal trisomies (eg, Down, Edward, and Patau syndromes), metabolic conditions (eg, diabetes, hypoglycemia, and galactosemia), Lowe syndrome, and congenital infections (eg, toxoplasmosis, rubella, cytomegalovirus, and herpes simplex [TORCH]).[3]
A comprehensive eye exam is necessary for evaluating congenital cataracts and determining visual significance. The red reflex should be visualized prior to dilation to determine if a central opacity of the lens is significantly obscuring the visual axis.
An irregular red reflex is the hallmark of visual problems. If an irregular red reflex is detected at the initial screening, this is an indication that a congenital cataract might be present and an ophthalmology consultation is warranted. Leukocoria, or white reflex, can be a presenting sign of a cataract.[9] In fact, in a 2008 study by Haider et al, 60% of patients who presented with leukocoria had congenital cataracts (18% unilateral and 42% bilateral).[10] Other causes included retinoblastoma (11% unilateral and 7% bilateral), retinal detachment (2.8% unilateral and 1.4% bilateral), persistent fetal vasculature (4.2%), and unilateral Coats disease (4.2%).[10]
After pupillary dilation, slit lamp examination of both eyes can confirm the presence of a cataract and also help in identifying the morphology of the cataract. Based on the morphology of the cataract, factors including visual significance, etiology, and prognosis may be determined. Common morphologies of congenital cataracts include anterior polar, fetal nuclear, lamellar, posterior polar, and total.[11] A dilated fundus examination is also recommended as part of the full ocular examination for both unilateral and bilateral cataract cases. If the cataract obstructs the view to the fundus, a B scan (ophthalmic ultrasound) is performed to evaluate for any posterior pathology such as a retinal detachment, persistent fetal vasculature, or posterior pole tumor.
Potential complications of visually significant congenital cataracts include the following:
For unilateral cataracts, work up may be deferred in the absence of any other systemic abnormalities.
For bilateral cataracts, laboratory studies to consider include CBC, CMP with calcium and phosphorus, TORCH titers, syphilis screen, galactose-1-phosphate uridyltransferase, urine test for reducing substances and amino acids, and genetic testing.
If the cataract obstructs the view to the fundus, a B scan (ophthalmic ultrasound) is performed to evaluate for any posterior pathology such as a retinal detachment, persistent fetal vasculature, or posterior pole tumor.
Other tests to consider include the following:
Medical therapy is directed at the prevention and treatment of amblyopia.
For visually significant cataracts, surgical intervention is necessary to remove the source of visual deprivation. For patients who are left without an intraocular lens (aphakic), appropriate correction of the refractive error either with contact lenses or aphakic glasses is necessary. Finally, in the case of unilateral cataracts, patching of the better seeing eye is needed to manage the resulting amblyopia.
Cataract surgery is the treatment of choice for visually significant congenital cataracts. To limit the severity of deprivation amblyopia, it is recommended that unilateral congenital cataracts be removed by 6 weeks of age and bilateral congenital cataracts be removed by 10 weeks of age.[3]
The procedure of choice is extracapsular cataract extraction with primary posterior capsulotomy and anterior vitrectomy. Vitrectomy instrumentation and irrigation/aspiration tools are used without phacoemulsification since the lens material is very soft in congenital cataracts. Pediatric eyes will develop a posterior capsular opacification, so primary posterior capsulotomy and anterior vitrectomy are required to minimize the need for a second surgical intervention.
With cataract extraction, the decision must be made whether to place an intraocular lens implant during the initial surgery. Age of surgery is an important factor in this decision. Intraocular lens implants are highly considered for patients ages 1 year and older. For younger patients, utility of intraocular lens implants is being investigated, especially since these patients can develop large refractive errors later in childhood if a lens is placed. The Infant Aphakia Treatment Study found that primary intraocular lens implantation was neither beneficial nor detrimental to visual outcomes after 10.5 years for patients ages 1 to 6 months old with unilateral congenital cataracts.[13]
If a child is left without an intraocular lens (aphakic), refractive correction with a contact lens or aphakic glasses will be required after surgery. If a child receives an intraocular lens implant, glasses are still necessary to account for residual expected refractive error. Of note, all children who have cataract surgery regardless of lens placement will require a bifocal lens to achieve distance and near vision.
A known complication of this surgery is aphakic glaucoma. While earlier intervention is important from the standpoint of amblyopia prevention and management, younger age at the time of cataract removal is associated with a higher risk of developing aphakic glaucoma.[14, 15]
An ophthalmology consultation is essential to prevent visual loss as well as to make the appropriate diagnosis of congenital cataracts. A genetics evaluation is warranted if there are bilateral congenital cataracts or any other systemic anomalies present.
If galactosemia is present, dietary restriction of galactose may reverse the progression of the classic "oil droplet" cataract.
Evaluation of the red reflex is essential not only in the newborn nursery, but also in subsequent pediatric office visits to identify and address the potential presence of a congenital cataract in a timely manner.
After surgical management of visually significant cataracts, patients require lifelong follow up. Throughout childhood, frequent monitoring and management of refractive error, amblyopia, and possible glaucoma is necessary.
Patients with congenital cataracts that are not visually significant also should be monitored to ensure that the cataracts do not progress to become visually significant.