Introduction:
A cataract is a condition where a layer of film forms over the otherwise healthy lens and causes blurred vision. It happens due to many factors in which chromosomes play an important role. Cataracts caused due to chromosomal defects are called congenital cataracts (cataracts present at birth or developed during childhood). They can be seen in one or both eyes. Congenital cataracts are a significant reason behind childhood blindness. These cataracts are diagnosed during regular health screenings or only when the parents notice leukocoria (white pupil seen especially in photography). If left untreated, it will badly affect the child's life.
What Is the Genetic Theory Behind Congenital Cataracts?
The eyes develop after 22 days of gestation (the period between conception and birth). It is an autosomal dominant inherited trait. Fibroblast growth factor, bone morphogenetic protein, and genetic factors encoding the proteins like PAX6, PITX3, and FOXE3 are crucial in developing the lenses. If any of the functions are deficient, lens development gets severely affected. The mutation of genes like the beta B2 crystallin gene (CRYBB2), intrinsic protein of lens fiber gene (MIP)1, and gamma D crystallin gene (CRYGD) play a very crucial role in the formation of congenital cataracts.
What Are the Birth Defects Associated With Congenital Cataracts?
The birth defects associated with congenital cataracts are:
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Congenital rubella (rubella virus infection in children causes eye abnormalities, deafness, and genetic heart attacks).
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Down syndrome (caused by extra chromosome 21).
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Galactosemia.
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Lowe syndrome.
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Ectodermal dysplasia.
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Familial congenital cataracts.
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Sjogren syndrome (an immune disorder characterized by dry eyes and mouth).
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Chondrodysplasia (a genetic disorder affecting bone and cartilage development and is often linked to dwarfism).
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Patau syndrome (a person having three copies of chromosome 13).
Other factors that cause congenital cataracts include diabetic mothers, antibiotics like tetracycline during pregnancy, trauma, and metabolic disorders.
What Are the Types of Congenital Cataracts?
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Anterior Polar Cataracts: It is well defined and located in the lens's front part. It is often small and will not need surgical intervention.
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Posterior Polar Cataracts: It is located on the backside of the lens.
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Nuclear Cataracts: It is seen in the central part of the lens and is a common form of congenital cataract.
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Cerulean Cataracts: It is also called blue dot cataracts due to the characteristic blue and white opacities found in the nucleus of the lens. It is caused by inheriting mutated genes. The child will often be asymptomatic until two years of age.
What Are the Symptoms of Congenital Cataracts?
The child will present with:
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Impaired vision in one or both eyes.
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White layer over the pupil (it usually is black).
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Nystagmus (eyes make repetitive, uncontrolled movements).
What Are the Complications of Untreated Congenital Cataracts?
Congenital cataracts should be treated in the early stages; otherwise, they might lead to,
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Strabismus (eyes do not align in a line - squint).
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Amblyopia (reduced vision in one eye).
How to Diagnose Congenital Cataracts?
Most of the time, children with congenital cataracts will not be able to express the problem with their vision, and the parents will never know until the ophthalmologist diagnoses it during routine tests. Early diagnosis of congenital cataracts is crucial to avoid complications like amblyopia, where normal vision can never be regained.
1. Red Reflex Test:
After the child is born, the doctor will put the baby through a few tests for up to six weeks, including a red reflex test. A red reflex test is done to study the layers of the eye along with the vitreous part (a fluid that fills the eye). This test is usually performed in a dark room. The child is taken inside a dark room. The doctor will sit 50 cm away from the child and use a direct ophthalmoscope with lens power at 0 to focus on the child's eye. The child is encouraged to look at the light source, and the light is directed at the eyes of the child. There will be a red reflex from each pupil. The examiner checks for the color and brightness in both eyes. Severe defects can be predicted if there is any difference in color and intensity.
2. Ultrasonography:
This test is used to study the eye and the orbit in detail. It is also helpful in estimating the prognosis of the case.
How to Manage Congenital Cataracts Surgically?
Once diagnosed with a congenital cataract, it is always advisable to opt for surgery immediately. If left untreated for a long time, significant complications may develop. Surgery is advised when the opacity is more than 3 mm in size. Blue dot cataracts will not need surgical correction since the vision is not severely affected and can be corrected with refractive eyeglasses.
Time of Surgery:
Surgery must be done before six weeks of age if the cataract is present in one eye (unilateral).
If the cataract is present in both eyes (bilateral), surgery has to be done before eight weeks.
Choice of Anesthesia:
General anesthesia with an endotracheal tube or a laryngeal mask airway is preferred. Usually, the child will be put on an intravenous perioperative analgesic which can be replaced with sub tenon (the space between the capsule and the sclera) block or topical lignocaine.
Surgery:
Generally, cataract surgery includes removing the cataract layer and placing an artificial intraocular lens. Cataract layers will be removed in children below one year, and eyeglasses will be prescribed. Artificial intraocular lens placement in children aged six months to one year requires further study. It is usually placed only after the age of 2.
Prognosis:
The success of cataract surgery highly depends on when the surgery is done. If it is not done during the early stages, complications occurring will hamper success. Regular follow-up is necessary. Parents should make sure the children wear the prescribed glasses regularly.
Conclusion:
Though a child affected by a congenital cataract is heart wrecking, it is easier to resolve the defect. With advancing medical technologies, cataract surgery has become highly reliable. Frequent eye checkups for the child will reduce the risk to a greater extent.
