Microphthalmia is an eye abnormality that arises before birth. In this condition, one or both eyeballs are abnormally small. In some affected individuals, the eyeball may appear to be completely missing; however, even in these cases some remaining eye tissue is generally present. Such severe microphthalmia should be distinguished from another condition called anophthalmia, in which no eyeball forms at all. However, the terms anophthalmia and severe microphthalmia are often used interchangeably. Microphthalmia may or may not result in significant vision loss.

People with microphthalmia may also have a condition called coloboma. Colobomas are missing pieces of tissue in structures that form the eye. They may appear as notches or gaps in the colored part of the eye called the iris; the retina, which is the specialized light-sensitive tissue that lines the back of the eye; the blood vessel layer under the retina called the choroid; or in the optic nerves, which carry information from the eyes to the brain. Colobomas may be present in one or both eyes and, depending on their size and location, can affect a person's vision.

People with microphthalmia may also have other eye abnormalities, including clouding of the lens of the eye (cataract) and a narrowed opening of the eye (narrowed palpebral fissure). Additionally, affected individuals may have an abnormality called microcornea, in which the clear front covering of the eye (cornea) is small and abnormally curved.

Between one-third and one-half of affected individuals have microphthalmia as part of a syndrome that affects other organs and tissues in the body. These forms of the condition are described as syndromic. When microphthalmia occurs by itself, it is described as nonsyndromic or isolated.

At a glance: Anophthalmia and Microphthalmia

• Signs: Being born without one or both eyes (anophthalmia) or with unusually small eyes (microphthalmia)

• Diagnosis: Prenatal tests, physical exam

• Treatment: Prosthetics, surgery

What are anophthalmia and microphthalmia?

Anophthalmia and microphthalmia are often used interchangeably. Microphthalmia is a disorder in which one or both eyes are abnormally small, while anophthalmia is the absence of one or both eyes. These rare disorders develop during pregnancy and can be associated with other birth defects.

What causes anophthalmia and microphthalmia?

Causes of these conditions may include genetic mutations and abnormal chromosomes. Researchers also believe that environmental factors, such as exposure to X-rays, chemicals, drugs, pesticides, toxins, radiation, or viruses, increase the risk of anophthalmia and microphthalmia, but research is not conclusive. Sometimes the cause in an individual patient cannot be determined.

What's the treatment for anophthalmia and microphthalmia?

There is no treatment for severe anophthalmia or microphthalmia that will create a new eye or restore vision. However, some less severe forms of microphthalmia may benefit from medical or surgical treatments. In almost all cases improvements to a child’s appearance are possible. Children can be fitted for a prosthetic (artificial) eye for cosmetic purposes and to promote socket growth. A newborn with anophthalmia or microphthalmia will need to visit several eye care professionals, including those who specialize in pediatrics, vitreoretinal disease, orbital and oculoplastic surgery, ophthalmic genetics, and prosthetic devices for the eye. Each specialist can provide information and possible treatments resulting in the best care for the child and family. The specialist in prosthetic diseases for the eye will make conformers, plastic structures that help support the face and encourage the eye socket to grow. As the face develops, new conformers will need to be made. A child with anophthalmia may also need to use expanders in addition to conformers to further enlarge the eye socket. Once the face is fully developed, prosthetic eyes can be made and placed. Prosthetic eyes will not restore vision.

How do conformers and prosthetic eyes look?

A painted prosthesis that looks like a normal eye is usually fitted between ages one and two. Until then, clear conformers are used. When the conformers are in place the eye socket will look black. These conformers are not painted to look like a normal eye because they are changed too frequently. Every few weeks a child will progress to a larger size conformer until about two years of age. If a child needs to wear conformers after age two, the conformers will be painted like a regular prosthesis, giving the appearance of a normal but smaller eye. The average child will need three to four new painted prostheses before the age of 10.

How is microphthalmia managed if there is residual vision in the eye?

Children with microphthalmia may have some residual vision (limited sight). In these cases, the good eye can be patched to strengthen vision in the microphthalmic eye. A prosthesis can be made to cap the microphthalmic eye to help with cosmetic appearance, while preserving the remaining sight.

Microphthalmia may be caused by changes in many genes involved in the early development of the eye, most of which have not been identified. The condition may also result from a chromosomal abnormality affecting one or more genes. Most genetic changes associated with isolated microphthalmia have been identified only in very small numbers of affected individuals.

Microphthalmia may also be caused by environmental factors that affect early development, such as a shortage of certain vitamins during pregnancy, radiation, infections such as rubella, or exposure to substances that cause birth defects (teratogens).

Isolated microphthalmia is sometimes inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. In some cases, parents of affected individuals have less severe eye abnormalities.

When microphthalmia occurs as a feature of a genetic syndrome or chromosomal abnormality, it may cluster in families according to the inheritance pattern for that condition, which may be autosomal recessive or other patterns.

Often microphthalmia is not inherited, and there is only one affected individual in a family.

Anophthalmia and microphthalmia can either be diagnosed during pregnancy or after birth. During pregnancy, doctors can often identify anophthalmia and microphthalmia through an ultrasound or a CT scan (special x-ray test) and sometimes with certain genetic testing. After birth, a doctor can identify anophthalmia and microphthalmia by examining the baby. A doctor will also perform a thorough physical exam to look for any other birth defects that may be present.

There is no treatment available that will create a new eye or that will restore complete vision for those affected by anophthalmia or microphthalmia. A baby born with one of these conditions should be seen by a team of special eye doctors:

• An ophthalmologist, a doctor specially trained to care for eyes
• An ocularist, a healthcare provider who is specially trained in making and fitting prosthetic eyes
• An oculoplastic surgeon, a doctor who specializes in surgery for the eye and eye socket

The eye sockets are critical for a baby’s face to grow and develop properly. If a baby has one of these conditions, the bones that shape the eye socket may not grow properly. Babies can be fitted with a plastic structure called a conformer that can help the eye socket and bones to grow properly. As babies get older, these devices will need to be enlarged to help expand the eye socket. Also, as children age, they can be fitted for an artificial eye.

A team of eye specialists should frequently monitor children with these conditions early in life. If other conditions arise, like a cataract or detached retina, children might need surgery to repair these other conditions. If anophthalmia or microphthalmia affects only one eye, the ophthalmologist can suggest ways to protect and preserve sight in the healthy eye. Depending on the severity of anophthalmia and microphthalmia, children might need surgery. It is important to talk to their team of eye specialists to determine the best plan of action.

Babies born with these conditions can often benefit from early intervention and therapy to help their development and mobility.

Microphthalmia occurs in approximately 1 in 10,000 individuals.