Congenital Cataract

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]  

Frequency

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]

Age

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.

Genetics

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]

Mortality/Morbidity

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.