The term congenital cataract refers to a lens opacity present at birth.
Congenital cataracts cover a broad spectrum of severity: whereas some lens opacities do not progress and are visually insignificant, others can produce profound visual impairment.
Congenital cataracts may be unilateral or bilateral, total or fractional.
They can be classified by morphology, presumed or defined genetic etiology, presence of specific metabolic disorders, or associated ocular anomalies or systemic findings.
Epidemiology
- Congenital cataract are responsible for nearly 10% of all vision loss in children world wide.
- Congenital cataract are one of the most common treatable causes of visual impairment and blindness during infancy, with an estimated prevalence of 1 to 6 cases per 10,000 live births.
Kinds
Congenital cataracts occur in a variety of morphologic configurations, including lamellar, polar, sutural, coronary, cerulean, nuclear, capsular, complete, membranous.
Among the congenital cataracts are most common:
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Сapsular - IIsolated opacity of anterior or posterior capsules of the lens. Size and shape of opacities are diverse. The degree of reduction depends on the size of the capsule opacification. Capsular cataract development may be caused by diseases of the mother during pregnancy or intrauterine inflammation.
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Polar - The impairment covers both capsule and the lens material nearby the anterior or posterior poles. In most cases it's bilateral cataracts. Size and shape are extremely various, which determines its effect on vision.
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Lamellar - The most common form of congenital cataracts. In the majority of cases are bilateral. Located in the center, around the transparent (or slightly turbid) nucleus. Vision is reduced always very significantly to 0,1 D and below.
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Nuclear - Develops in both eyes, has a distinct hereditary character, in most cases vision is reduced to a very low level - 0,1 D and below. In cases where opacity is restricted to embryonic nucleus, vision may be reduced with little or no decrease at all.
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Complete - In most cases it's bilateral. The clinical picture is diverse and depends on the degree of opacification of the lens. At full development of cataract the entire lens is muddy. The child is blind, has only light perception. May develop before birth or in the first months of mature life.
The most important feature of complete cataract is its combination with other defects in eye development (microphthalmia, choroid coloboma, macular hypoplasia, nystagmus, strabismus, etc.). Full cataracts may sometimes have a tendency to resorption and then in the pupil may remain pellicle - membranous cataract. -
Сomplicated - The reason for its development can be galactosemia, diabetes, rubella virus and other serious diseases. Often accompanied by other birth defects (heart defects, deafness, etc.).
Etiology
In general, approximately one-third of congenital cataracts are a component of a more extensive syndrome or disease (e.g., cataract resulting from congenital rubella syndrome), one-third occur as an isolated inherited trait, and one-third result from undetermined causes. Metabolic diseases tend to be more commonly associated with bilateral cataracts.
- Genetic & Metabolic (Down syndrome, Hallermann-Streiff syndrome, Lowe syndrome, Galactosemia, Cockayne syndrome, Marfan syndrome, Trisomy 13- 15, Hypoglycemia, Alport syndrome, Myotonic dystrophy, Fabry disease, Hypoparathyroidism, Conradi syndrome, Incontinentia pigmenti).
- Infections (Toxoplasmosis, Rubella, Cytomegalovirus, Herpes Simplex (HSV-1, HSV-2, Other (Coxsackievirus, Syphilis, Varicella-Zoster, HIV, and Parvo B19)).
- Anomalies (Aniridia, Anterior segment dysgenesis, Persistent fetal vasculature (PFV), Posterior lenticonus)
- Toxic (Corticosteroids, Radiation)
Genes involved in congenital cataract
Approximately 50% of all congenital cataract cases may have a genetic cause which is quite heterogeneous. It is known that different mutations in the same gene can cause similar cataract patterns, while the highly variable morphologies of cataracts within some families suggest that the same mutation in a single gene can lead to different phenotypes. More than 25 loci and genes on different chromosomes have been associated with congenital cataract. Mutations in distinct genes, which encode the main cytoplasmic proteins of human lens, have been associated with cataracts of various morphologies, including genes encoding crystallins (CRYA, CRYB, and CRYG), lens specific connexins (Cx43, Cx46, and Cx50), major intrinsic protein (MIP) or Aquaporin, cytoskeletal structural proteins, paired-like homeodomain transcription factor 3 (PITX3), avian musculoaponeurotic fibrosarcoma (MAF), and heat shock transcription factor 4 (HSF4).
Evaluation
All newborns should have screening eye examinations, including an evaluation of the red reflexes.
- The red reflex test is best performed in a darkened room and involves shining a bright direct ophthalmoscope into both eyes simultaneously from a distance of 1– 2 ft. This test can be used for routine ocular screening by nurses, pediatricians, and family practitioners.
- Retinoscopy through the child's undilated pupil is helpful for assessing the potential visual significance of an axial lens opacity in a pre-verbal child. Any central opacity or surrounding cortical distortion greater than 3 mm can be assumed to be visually significant.
- Laboratory Tests : In contrast to unilateral cataracts, bilateral congenital cataracts may be associated with many systemic and metabolic diseases. A basic laboratory evaluation for bilateral cataracts of unknown etiology in apparently healthy children includes:
- - Urine test for reducing substance, galactose 1-phosphate uridyltransferase, galactokinase, amino acids
- - Infectious diseases: TORCH and varicella titers, VDRL
- - Serum calcium, phosphorus, glucose and ferritin
Surgery
In general, the younger the child, the greater the urgency in removing the cataract, because of the risk of amblyopia. For optimal visual development in newborns and young infants, a visually significant unilateral congenital cataract should be detected and removed before age 6 weeks, and visually significant bilateral congenital cataracts should be removed before age 10 weeks.
Safest and most effective method of treatment is phacoemulsification. With a diamond tool surgeon creates a micro-incision no more than 2.5 mm and all further manipulation produces through it. Using ultrasound lens is converted into an emulsion and is removed from the eye.
If there are no contraindications as associated severe eye pathology, the intraocular implantation of the foldable lens in unilateral cataract occur simultaneously. Through the micro-incision in the capsule, which previously housed the muddy lens, enter a flexible lens in a folded state, which is itself unfolds inside the eye and fixed reliably.
