A Consultant Ophthalmologist at the Lagos State University Teaching Hospital, Prof. Bola Adekoya, says congenital blindness can be caused by genetic defect, and is a condition common in consanguineous marriage — that is, a union between individuals who are closely related.
The renowned glaucoma specialist, who heads the Ophthalmology Department of LASUTH, noted that the risk of autosomal recessive disorders increases in offspring coming from such union due to increased likelihood of receiving recessive genes from both parents.
Adekoya explained that autosomal recessive is one of the several ways that a trait, disorder, or disease can be passed down through families.
“It means two copies of an abnormal gene must be present in order for the disease or trait to develop. To have an autosomal recessive disorder, one must inherit two mutated genes, one from each parent,” she added.
The glaucoma expert further said there is a 50/50 chance that parents with a particular type of disease will have it transferred to their offspring.
“Congenital blindness is more particular in places where people marry within family. The situation can arise where you have family members such as first cousins or even a little bit of distant cousins getting married.
“If any of the individuals have a genetic disorder, children from the union are most likely to inherit it.
“This is because the genetic disorder runs in the lineage and it’s more likely to be in another of the family member. When they now marry and have children, that genetic abnormality has a higher chance of manifesting,” Adekoya said.
According to a report in peer-reviewed online journal, BMJ, marrying close family members is a tradition in many countries, and which leads to higher rates of genetic disorders.
It noted that one billion people worldwide live in countries where marriage among relatives is common, adding that one in three out of the number is married to a second cousin or closer relative, or is the progeny of such a marriage.
“The frequency of genetic disorders among such children is around twice those in children of non-related parents,” the article stated.
Multidisciplinary online publication, Nature, advised that consanguineous couples should be informed about the increased risk of having children with congenital disorders, noting that on the average, first cousins have an extra risk of 1.7 to 2.8 percent of having a child with an autosomal recessive disorder.
On how often she attends to patients with congenital blindness linked to genetic defects, the consultant ophthalmologist said as a specialist, she gets to see some during clinic days, noting that it is not uncommon.
To avoid the deformity from continuing, Adekoya said, the best solution is for family members not to intermarry in the first place.
“The best thing is to prevent it from occurring in the first place,” she advised.
“We don’t want it to occur. Once family members intermarry, the possibility of having abnormality occurring in any organ in the body is very high.
“It increases their chances of having genetic problems. If the person marries into another family, there might be an issue, which might be much suppressed.
“However, marrying within the same family will make the abnormal gene dominant, and the offspring will get one from the mother and one from the father. So, there will be no normal gene for the child to be able to compensate with.”
The glaucoma expert further said any family that has been experiencing cases of congenital blindness concurrently should visit the hospital for genetic counselling and medical investigation to find out why it keeps occurring.
“Such medical investigation might trigger a change within the family. Such a family should carry out genetic screening, which might require some high tech equipment to take the DNA, which will be used to carry out genetic mapping to find out where the abnormal gene is.
“Perinatal screening can also be carried out on a foetus when the woman in such a union is pregnant. This will help to determine the inherent type of abnormality that is present.
“However, these equipment are mostly available in more technologically advanced countries.”
Adekoya said for a child with congenital blindness arising from consanguineous marriage, the only thing that can be done is to treat whatever abnormality that presents, and which appears treatable, adding, “Such treatment might involve constant medication and glaucoma or cataract surgery.”
According to the World Health Organisation, globally, an estimated 295,000 newborns die within 28 days of birth annually due to congenital anomalies.
The WHO noted that congenital anomalies can contribute to long-term disability, which may have significant impacts on individuals, families, health-care systems, and societies.
It pointed out that the most common, severe congenital anomalies include heart defects, neural tube defects and Down syndrome.
“Although congenital anomalies may be the result of one or more genetic, infectious, nutritional or environmental factors, it is often difficult to identify the exact causes.
“Some congenital anomalies can be prevented. Vaccination, adequate intake of folic acid or iodine through fortification of staple foods or supplementation, and adequate antenatal care are just three examples of prevention methods,” the WHO stated.
Speaking further on other likely causes of congenital blindness, Adekoya said it could also be due to a problem that occurred during pregnancy, which can be caused by teratogenic agents.
“A teratogen is an agent that can disturb the development of the embryo or foetus, and is likely to cause congenital malformation or birth defect in the foetus. These things include maternal infections, chemicals, drugs and inadvertent exposure to radiation.
“The defect might occur in the eye, body, heart or ear. It might just be an abnormality occurring singularly or in association with each other,” she noted.
Adekoya explained that there are some forms of infections known as ‘Torch Syndrome’ that can also distort full development of the eye, resulting in blindness.
She explained that Torch syndrome is a group of infectious diseases like rubella, herpes simplex, syphilis, among others, that can cause problems for an unborn baby.
“Fortunately, we have immunisation against Rubella, for instance, which can prevent such abnormalities.
“If pregnant women and children are well immunised, it would reduce the chance of some of such malformation if the Torch infections occur in the mother.
According to WebMD, if a woman gets one of the Torch infections while pregnant, and it spreads through the blood, the foetus can get it, too.
“Because they are still developing in the uterus, their immune system most likely won’t be able to fight it off.
“If the disease stays in their body, their organs might not develop correctly. How sick your baby can get depends on several things, including what the condition is and how far along they are in their development.
“But a number of problems can happen, from jaundice (yellowish skin or eyes) and hearing problems to miscarriage and stillbirth,” WebMD stated.
Another factor that can cause congenital blindness, Adekoya said, is Ophthalmia Neonatorum, an eye infection that occurs within the first 30 days of life.
She said it is contracted during passage through a birth canal infected with a sexually-transmitted disease.
“The infection can be serious enough to cause blindness. It can range from complete absence of the eye, to the eye being there but is very small or very big — these are the children that we say have congenital glaucoma.
“The abnormality might have to do with a specific structure of some aspect of the eye. Maybe the cornea, which is meant to be black, will appear whitish, and this is known as corneal opacity.
“Some children could have a congenital cataract, while others will have problems with the retina, which is like a film at the back of the eye. But like I said earlier, by far, the most common will be due to genetic abnormalities,” the eye expert said.
Adekoya warned pregnant women against consuming drugs that are not prescribed by their obstetrician and gynaecologist, stressing that it can also lead to birth defects.
“Let me not also forget some drugs. That is why pregnant women need to be careful about the type of medication they take because it could cause extensive damage.
“We are not just talking about orthodox medications; even local herbal concoctions, whose properties we don’t know or how they may affect an unborn child, should be prohibited.
“However, I advise that once a baby is born with any eye problem, the important thing to do is to see an eye specialist immediately.”
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