What is Coloboma?

The development of a baby's eyes in the womb is a complex process. When this development is interrupted, conditions like coloboma can arise.

This condition can result in missing tissue in one or more of the eye's structures, potentially affecting vision from birth.

Let’s discuss practical information about coloboma, its impact on vision, and how to thrive despite this condition.

How Does a Coloboma Happen?

During the early stages of pregnancy, a special groove called the optic fissure runs along the underside of each developing eye. By week seven, this fissure normally seals shut, completing the formation of eye structures. 

However, if the fissure doesn't fully close, it leaves a gap in the eye tissues, known as a coloboma. The different types of colobomas are characterized by their location:

• Lens coloboma. A lens coloboma happens when part of the zonular fibers that support the lens is missing. When this occurs, the lens can lose its normal shape, potentially resulting in a refractive error or amblyopia (lazy eye). 
• Iris coloboma. A visible notch or keyhole shape in the colored part of the eye.
• Macular coloboma. A macular coloboma occurs when the macula doesn't develop normally. This type can have a significant impact on vision.
• Eyelid coloboma. An eyelid coloboma appears as a missing piece of the upper or lower eyelid. They usually look like a notch in the eyelid. Severe cases of this condition can cause the visible part of the eyelid to be completely missing.
• Retinal or choroidal coloboma. Gaps in the retina or underlying choroid can affect central vision.
• Optic nerve coloboma. A gap involving the optic nerve head.

The “typical” or common coloboma is located in the eye's inferonasal (lower inner) area. Meanwhile, “atypical” colobomas are located elsewhere but are uncommon.

How Do Colobomas Affect Vision?

How much your child’s vision will be affected depends on the coloboma’s size, location, and which structures are involved. For instance, iris colobomas typically don't significantly impair vision.

Retinal or optic nerve colobomas, on the other hand, often lead to vision problems. They commonly result in blind spots or a loss of the upper visual field because the gap in the retina affects how the eye captures images.

Meanwhile, some types, such as iris coloboma, cause a visible anomaly in the iris. Other types, like eyelid coloboma, can cause excessive dryness in the eye.

What are the Symptoms of Coloboma?

The symptoms of a coloboma vary depending on the type. Some people don’t have any symptoms. Others may experience vision problems, such as:

• Increased light sensitivity 
• Poor vision
• Vision loss or blindness
• Blind spots or vision impairment in a specific area of the field of vision

What Causes Coloboma?

The exact cause of ocular coloboma can vary. However, causes typically include:

• Genetic factors. Having a family history of coloboma can increase your risk of developing it. Additionally, certain genetic disorders like cat-eye syndrome can cause coloboma.
• Environmental factors. Certain environmental factors, such as alcohol use during early pregnancy, can increase the risk of coloboma.
• CHARGE syndrome. CHARGE syndrome is present at birth and can affect many parts of the body. It stands for coloboma, heart defect, atresia choanae, restricted growth and development, genital abnormality, and ear abnormality.
• Wolf-Hirschhorn syndrome. Wolf-Hirschhorn syndrome (WHS) is a rare genetic disorder. Symptoms can affect many parts of the body.
• Goldenhar syndrome. This rare congenital condition is characterized by irregular eye, ear, and spine development.
• Microphthalmia. One or both eyes are atypically small. In some cases, the eyeball may be severely underdeveloped but not completely absent.

What are the Risks of Coloboma?

While some children with coloboma experience isolated eye issues, many have associated systemic features. For instance, CHARGE syndrome often includes heart defects, hearing impairment, and developmental delays. 

Other conditions, such as renal coloboma syndrome and cat eye syndrome, link eye anomalies to kidney and other organ concerns. If your child has chorioretinal colobomas, they may be at risk of retinal detachment.

Additionally, ocular coloboma can increase your child’s chances of developing eye conditions later in life, such as:

• Cataracts 
• Glaucoma 
• Refractive errors
• Retinal detachment
• Growth of new blood vessels in the back of the eye

Treatment Options for a Coloboma 

While there’s no cure for coloboma, there are several treatment options that can improve your child’s vision and relieve symptoms.

These include:

• Glasses or contacts. People with refractive errors due to coloboma can wear eyeglasses or contact lenses to see more clearly. People with iris colobomas may need to wear colored contacts to make their pupils rounder.
• Low vision aids. Low-vision devices can help patients see if their vision loss can’t be corrected with contacts or glasses.
• Eye patch or eye drops. Children with coloboma in one eye may benefit from wearing an eye patch or eye drops. These treatments help prevent lazy eye.
• Surgery. Various surgical procedures can treat different types of coloboma. For example, surgery can correct eyelid coloboma and iris coloboma.