Anophthalmia

Anophthalmia Definition

Anophthalmia, also referred to as Anophthalmos, is a congenital defect that leads to absence of the eyes in a newborn. It is a very rare condition characterized by the lack of the ocular tissue and the globe of the eye. This defect can occur both unilaterally (affecting one eye) and bilaterally (involving both eyes). The disorder occurs during pregnancy due to certain genetic factors and can be linked with various other birth defects. It can even lead to fetal death and stillbirth. Sometimes, an affected infant dies shortly after birth.

Anophthalmia Incidence

This is a very rare condition, with the exact prevalence statistics still not being known. A recent study, carried out in England, shows the disorder to occur in 1 out of every 10,000 births.

Anophthalmia Classification

The disorder is classified into the following three categories:

Primary Anophthalmos

It denotes complete absence of the ocular tissue as the brain region responsible for the development of the eye fails to work properly.

Secondary Anophthalmos

The eyes begin to develop normally, but the development stops prematurely due to some reason. As a result, the infant is born with extremely small eyes or only some residual eye tissue.

Degenerative Anophthalmos

In this type of the deformity, the eyes start to develop only to be degenerated due to some unknown causes. Reduced supply of blood to the eyes can be one of the causative factors.

Anophthalmia Causes

In many cases, it is not possible to determine the exact causes of this defect. Scientists have found that abnormal chromosomes and genetic mutations may be responsible for it in some children. Researches also suggest that various environmental factors, including exposure to chemicals, x-rays, pesticides, drugs, toxins, viruses and radiation can increase the risk of developing the disorder. Vitamin A deficiency in the mother during pregnancy is also counted among the risk factors of Anophthalmos.

Anophthalmia Genetics

Most cases of the condition are caused by genetic factors with mutations in the Sox2 gene being the factor responsible.  In these cases, it is known as Sox2 Anophthalmia Syndrome. The Sox2 gene controls the production of Sox2 protein, which is responsible for binding certain other genes to specific regions of DNA to regulate their activities. The protein also has a vital role in proper eye development. Mutations in the Sox2 gene hamper the Sox2 protein production. This disrupts the functioning of the protein and interrupts the maturation of the eyes of the fetus.

This form of the disorder is inherited in an autosomal dominant pattern. Sometimes, the parent carries the mutated gene only in sperm cells or eggs which is passed on to the offspring. This is referred to as germline mosaicism. At least thirty-three different Sox2 gene mutations have been identified to cause the defect. Some of these mutations stop the formation of Sox2 protein while others produce a non-functional type of the protein.

Anophthalmia Symptoms

Infants with the disorder are born without eyes, which leads to small bony orbit along with constricted mucosal socket, reduced palpebral fissure, short eyelids and malar hypoplasia. The severity of the symptoms generally varies from one patient to another. Babies born with the congenital defect can have the following symptoms:

  • Endocrine disturbance
  • Mental retardation
  • Short stature
  • Diabetes Insipidus
  • Prominent forehead
  • Ear anomalies and hearing loss
  • Epilepsy
  • Delayed puberty
  • Hypogonadism
  • Asymmetrical face
  • Hydrocephaly
  • Low set ears

Anophthalmia Associated Conditions

This disorder is often associated with the following birth defects:

  • Severe brain malformations
  • Pituitary malformation
  • Cleft lip
  • Cleft palate
  • Malformed brain ventricles
  • Scalp defect
  • Narrow pituitary stalk
  • Hypothalamus malformation
  • Thick hypothalamus

Other conditions commonly associated with it include:

  • Waardenberg Syndrome
  • Goldenhar-Gorlin Syndrome
  • Lenz Syndrome
  • Trisomy 13

Anophthalmia Diagnosis

The diagnosis can be done in two phases, the prenatal diagnosis and the postnatal diagnosis.

Prenatal Diagnosis

This can be done by:

Ultrasound

This test is useful for detecting the condition during gestation. However, its resolution makes it impossible to use the exam for the purpose before the second trimester. The 3D ultrasound and 4D ultrasound can produce more accurate images of the fetus’s eyes during pregnancy, which makes them a better alternative to standard ultrasound.

Amniocentesis

This test can also be used for this purpose. However, Amniocentesis often shows a negative result as it can diagnose the defect only if it is caused by chromosomal abnormality. But, chromosomal abnormalities very rarely lead to the condition.

Postnatal Diagnosis

It can be conducted through:

MRI and CT scan

These tests are used for scanning the orbits and the brain. They help a diagnostician to observe the internal structures of the globe as well as the extraocular muscles and optic nerve.

Physical examination

The diagnosis can be made by physicians, especially ophthalmologists, by thoroughly examining the newborn child. Sometimes, molecular genetic tests are used for detecting associated gene mutations.

Anophthalmia Differential Diagnosis

It is important to rule out the following conditions, which give rise to similar signs and symptoms, while diagnosing this disorder:

  • Severe Microphthalmia
  • Cryptophthalmos
  • Cystic Eye

Anophthalmia Treatment

At present, it is not possible to restore the vision n the absent or malformed eyes of patients. However, prosthetic eye and cosmetic surgery can be used to make the defect less noticeable.

Image of Anophthalmia

Picture 1 – Anophthalmia Image

Prosthetic Eye

Prosthetic specialists can manage the deformity by fitting a conformer into the affected eye. The conformer, made of clear plastic, can promote the growth and expansion of the socket. However, the conformer has to be changed with the growth and development of the child’s face. An expander may be required for expanding the socket before the conformer can be fitted into it. The conformer is usually replaced with a prosthetic eye once the child reaches 2 years of age. Patients should go for regular checkups to ensure that the prosthetic eye fits properly.

Cosmetic Surgery

A number of physical deformities can occur unless proper care is taken for expanding the orbit. In case any of these deformities occur, it is important to wait until the child is at least 2 years old before attempting to surgically correct them. Eye surgeries, such as lower eyelid tightening and upper eyelid ptosis, may be necessary. These surgeries are useful for restoring the function of various surrounding structures including the eyelid, which helps to improve the appearance of patients.

Anophthalmia Prognosis

The loss of vision caused by the defect is not treated, so there is no prognosis for Anophthalmos. However, cosmetic surgery and prosthetic eye placement surgery can help improve the quality of life of patients by minimizing their facial deformity.

Anophthalmia Prevention

It is not possible to prevent the disorder as it is usually caused by certain genetic factors. Prenatal testing is available to determine if an unborn child has the defect. Genetic counseling may be useful for couples with a family history of Anophthalmos to check whether they are carrying the abnormal gene. However, most of the patients do not have a family history of the birth defect.

Anophthalmia Support Groups

There are various organizations that provide facts and information regarding Anophthalmos to help the patients and their families to fight the condition. These include:

The Eyecare Trust

PO Box 804, Aylesbury

Buckinghamshire

HP20 9DF

Tel: 0845 129 5001

Email: info@eyecaretrust.org.uk

Website: http://www.eyecaretrust.org.uk/

International Children’s Anophthalmia & Microphthalmia Network (ICAN)

C/o Center for Developmental Medicine and Genetics

5501 Old York Road

Genetics, Levy 2 West

Philadelphia, Pennsylvania 19141

Phone: 1-800-580-ican

Email: ican@anophthalmia.org

Website: http://www.anophthalmia.org/index.shtml

 

Anophthalmia is an incurable birth defect affecting the eye development of the fetus. Children born with the condition remain completely or partially blind for entire life. However, proper medical care can help them to lead a relatively normal life and participate in suitable social activities.

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