Ablepharia: Description, Causes, and Risk Factors:
Congenital absence of the eyelids.
Ablepharia is a rare congenital eye defect in which the lid folds fail to separate in the embryo, resulting in a continuous sheet of skin from the forehead to the cheeks covering the eyes.
The skin over the eye is blended with the cornea, which is usually malformed. Also known as ablepharon or complete congenital symblepharon, ablepharia may be unilateral or bilateral. Its mode of genetic transmission is usually autosomal recessive, present in 15% of cases, particularly in consanguineous marriages. It usually affects siblings and lacks vertical transmission. It affects both genders and has no known chromosomal abnormality.
The pathogenesis of this condition is unknown. The most characteristic malformation present in this condition occurs in areas which remain temporarily fused in utero like the eyelids, the digits, and the vagina. The separation of eye lids occurs by a process of controlled necrosis of palpebral tissue between 17-18 weeks of gestation. Some attribute ablepharia to the defect in gene responsible for this programmed cell death. Researchers found adhesions of lens to the inner aspect of the layer of skin, and connective tissue covering the cryptophthalmic eye as a common feature. So they argued ;that the lid anomalies are sequelae to abnormal lens development. A role for vitamin A metabolism has also been suggested as a pathogenic mechanism from the observation in animal models in which mothers had hypovitaminosis A.
Other proposed theories include primary failure - of the ectodermal and mesodermal differentiation, intrauterine inflammation producing fusion of the eyelids to a globe, amniochorionic bands with pressure on eyelids and defective differentiation of the conjunctiva.
Most of the cases of isolated ablepharia are sporadic. The pattern of inheritance in our family with 2 sibs born to consanguineous parents is highly suggestive of autosomal recessive type. Prenatal diagnosis in severe cases is possible if two of the four features, viz., microphthalmia, obstructive uropathy, syndactyly, and oligohydramnios are present.
Due to multiple malformations of differentbody organs, a child with ablepharia is likely to suffer from at least partial visual,hearing or speech impairment, among othersymptoms.Another co-morbidity found in mostchildren with ablepharia may include intellectualimpairment is mainly caused by hydrocephaly(an abnormal amount of water within thebrain) or malformation (in some cases evenabsence) of one of the brain cavities.Abnormalities of kidneys, lungs anddigestive system are also quite commonin patients. Renal malfunctions in affectedinfants may include improper development(dysplasia), underdevelopment (hypoplasia)or absence of one or both kidneys (unilateralor bilateral renal agenesis).The most serious and life-threateningabnormalities associated with ablepharia are those of the kidneys and thelarynx. Lack of kidney function or blockageof the larynx is usually the cause of death forthose who are stillborn or die within the firstyear of infancy.25% of affected infants are stillborn while 20% die before the age of oneyear from renal or laryngeal defects. Ifthese anomalies are not present, the lifeexpectancy is almost normal.Although complications of the ablepharia are manifested as secondaryconditions, symptoms or other disorders,the distinction between symptoms andcomplications is unclear or arbitrary in manycases.
Differential diagnoses of ablepharia are anophthalmos and microphthalmos. Both are also rare conditions, arising from abnormal development of the optic vesicle and better differentiated histologically by orbital sections.
Ultrasonographic diagnosis of the syndrome is now feasible at 18 weeks gestation. It can be made if two of the following signs are present:
Microphthalmia - one eye being abnormally small.
- Enlarged echogenic lungs.
- Oligohydramnios - deficiency in amniotic fluid during pregnancy.
Management of complete ablepharia is difficult. Extensive reconstructive surgery is involved, including separation of the lids and placement of mucous membrane grafts to allow a conformer or prosthesis to be fitted. Reconstruction of the left eyelid coloboma involves several stages and the use of ear cartilage graft under the skin membrane over the globe to increase mass and act as a tarsal plate or the use of mucosal graft to cover the raw surface of the inner side of the upper lid and globe area.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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