Coloboma

This underdeveloped tissue is normally in the lower nasal (down and towards the nose) area of the eye.It occurs in about 1 in 5,000 births and develops at around five to seven weeks of pregnancy. A coloboma is present from birth and remains into adulthood.

Coloboma can

• affect one eye (unilateral) or both eyes (bilateral)
• affect different parts of the eye
• be small to large in size
• affect vision. This relates to the type and size of the coloboma and whether it is in one or both eyes

This page contains a summary of our information on coloboma. To read our full information, download our factsheet:

Coloboma forms during pregnancy while a baby is developing. The buds that become the eyes develop during the second month of pregnancy. As the eyes develop, the bottom of the eyeball fuses together in a seam-like join. In some pregnancies, this seam doesn’t join completely, affecting how fully some structures form. This causes missing tissue (coloboma) at the bottom of the structures being formed.

Coloboma can affect one or more structures within the eye. These include:

Iris

Coloboma can affect the iris at the front of the eye, meaning this tissue has not developed fully. The pupil in the centre of your iris can be oval or more keyhole shaped, depending on the size of the coloboma.

Ciliary body

Coloboma can affect tissue behind the iris called the ciliary body. Muscles in the ciliary body are attached to strands called zonules which hold the eye’s natural lens in place. If the ciliary body is affected by coloboma, the zonules will not provide equal support for the lens all the way round. This alters the lens shape by causing a notch or dent.

Retina and choroid (chorioretinal)

The retina and the choroid are layers of tissue which line the back of the eye. The choroid is the layer behind your retina, and it contains blood vessels that keep your retina healthy. Underdeveloped retinal and choroidal tissue is known as chorioretinal coloboma.

Optic disc

The retinal area where the optic nerve leaves the back of your eye is called the optic disc. An underdevelopment of this part of the optic nerve is known as an optic disc coloboma.

Yes, coloboma can affect a person’s vision. How much will depend on:

• the size of the coloboma – how much of the tissue is underdeveloped
• the type of coloboma – what structures of the eye the coloboma is affecting
• whether coloboma is in one or both eyes

It may be hard to tell how much your child’s sight is affected when they are very young. It’s therefore important they attend their hospital appointments as advised by their ophthalmologist (hospital eye doctor) and have regular eye examinations with their optometrist (optician). This gives them the best chance of developing their best possible vision.

In children, treatment may be given to make sure their vision develops fully as possible. This might include:

• Glasses or contact lenses to correct for short sightedness (myopia), long sightedness (hyperopia) or astigmatism. These focusing errors are not caused by the coloboma itself and glasses and contact lenses cannot improve any sight loss that results from the coloboma. However, correcting any additional focusing errors is important so their sight develops as well as it can.
• Patching or occluding one eye. If the coloboma is in one eye only, or it is more in one eye than the other, the brain can ‘choose an eye’ meaning that the other becomes weak. This is called amblyopia (lazy eye) and may be treated with eye patches in some cases.

It’s also important for adults with coloboma to have regular eye examinations. Regular checks ensure their overall eye health is monitored over time.

This will depend on the type of coloboma that’s present.

Iris coloboma

People with only iris coloboma may have good vision. However, iris coloboma can cause light sensitivity (photophobia) in bright conditions. Iris coloboma can mean excess light enters the eye, causing glare. Glare affects a person’s quality of vision and can cause discomfort.

Ciliary body coloboma

Vision is likely to be blurred when there is ciliary body coloboma. This is because it causes a notch or dent in the eye’s natural lens, changing its shape and ability to focus clearly. There may also be some degree of cataract in this eye. A cataract means the lens is cloudy instead of being clear. This cloudiness can cause symptoms such as blurred or misty vision, colours appearing dull and glare in your vision.

Chorioretinal (choroid and retina) coloboma or optic disc coloboma

Some people with chorioretinal coloboma may not be aware of any visual symptoms. However, the more retinal tissue that is missing, the more likely their sight is noticeably affected. Chorioretinal coloboma affects the upper field of vision (awareness of what’s above when looking straight ahead).

A person’s central vision is likely to be poor if their chorioretinal coloboma is large or they also have optic disc coloboma. If both eyes are affected by optic disc coloboma, they may also have nystagmus. Nystagmus is an eye condition where the eyes move constantly and uncontrollably.

In many cases, iris coloboma requires no treatment. However, special contact lenses can be helpful for some people, to make the keyhole-shaped pupil look rounder. This reduces light sensitivity and improves the eye’s cosmetic appearance.

For some people, surgery is an option. The gap in the iris is sewn together to correct the pupil shape and reduce light sensitivity. Your ophthalmologist will be able to discuss any treatment options with you that may be of benefit.

There is treatment available for other eye conditions which are associated with coloboma.

Sometimes, coloboma can increase the risk of other eye conditions. If you have coloboma, an optometrist or ophthalmologist will monitor for these conditions possibly developing as part of your eye health check. Therefore, it’s important to have regular eye examinations as often as you’re advised. If you develop new symptoms or are concerned about your sight between appointments, you should have your eyes examined as soon as possible.

Other eye conditions that can be associated with coloboma include:

• Strabismus (squint) and amblyopia (a “lazy eye”)
• Glaucoma
• Retinal detachment
• Choroidal neovascularisation
• Cataract.

Emotional support and counselling services

It’s completely understandable to be upset when you or your child is diagnosed with coloboma. You or your child may have normal vision or there may be some degree of sight loss. For a child, it may be difficult to predict to what extent their vision might be affected in the long term. You may find yourself worrying about the future and how you or your child will cope. You may find yourself wondering how coloboma will affect education or employment and future opportunities for you or your child.

It can sometimes be helpful to talk about how you’re feeling with someone outside of your circle of friends or family. At RNIB, we can help with our Counselling and Wellbeing team. Your GP or social worker may also find a counsellor for you if you feel this might help.

The Eye Care Liaison Officer (ECLO)

Your eye clinic may have a sight loss advisor working alongside the doctors and nursing staff. This advisor may be known as either the Eye Care Liaison Officer (ECLO), the Vision Support Officer or the Early Intervention Support Officer. They are on hand within your hospital or local sight loss charity to provide you with further practical and emotional support about eye health. To find out if there is ECLO support in your area, please contact your eye clinic directly or contact our Helpline on 0303 123 9999.

Alternatively, you can call our Helpline to speak to our advisors within our Eye Health Information service, as they would be happy to discuss any questions you may have.

Making the most of your sight

You may find some tasks are made easier by making things bigger and bolder. Using contrasting colours can also help to make some things stand out. An example of this could be making the edges of steps stand out using contrasting colours. When you have coloboma, you’ll be more comfortable if your environment causes you minimal glare. This can involve the lighting around you and the devices you’re using.

The low vision assessment

A low vision assessment may help if you’re struggling to see detail even when wearing your glasses or contact lenses. You can ask your ophthalmologist, optometrist or GP about having a low vision assessment and whether it’s appropriate for you. During this assessment, a low vision specialist can discuss with you how different magnifying aids and better lighting can help make things easier to see.

Education

Having the right support at an early age can make a big difference to children with sight loss due to coloboma. It’s important for the local authority to be aware of any specialist educational needs a child has so that a plan can be put in place to provide for this.

Local authorities can provide a specially trained qualified teacher of children and young people with vision impairment (QTVI). The QTVI can work alongside children and their families and provide information on development, play, and education. There is also educational support available within RNIB. Our family advisors can provide advice and information for young people up to the age of 25. You can get in touch with this team by calling our Helpline on 0303 123 9999.

Employment

If you have sight loss, you may be worried about finding work or staying in your job. Our employment advisors can provide specialist support and advice about employment for people with sight loss. You can contact this team via our Helpline on 0303 123 9999.

Assistive technology

There is also technology available that can help with low vision. Many smart phones and tablets are already equipped with in-built software that can be helpful. This can enable people with low vision to access information. There are also specific apps and low vision devices that may help too.

Computer software programmes are available that can also be installed. Our Digital Skills advisors would be happy to chat to you about the assistive technology that is available. You can get in touch with this team by calling our Helpline on 0303 123 9999.  

Social services support

Your local social services should also be able to offer local support if you have low vision. They can provide support with staying safe in your home and getting out and about safely.

Registration

You can ask your ophthalmologist whether you or your child is eligible to register as sight impaired (SI, previously referred to as partially sighted) or severely sight impaired (SSI, previously referred to as blind). Eligibility will depend on how much sight has been affected by coloboma. Registration can open up a host of benefits, including help from social services as well as financial concessions.  Even if you or your child is not registered, a lot of this support is still available to you.

Useful contacts

• MACS (Microphthalmia, Anophthalmia & Coloboma Support) can provide support and information to parents and carers of children with microphthalmia, anophthalmia, coloboma and related conditions.
• LOOK UK supports young people (up to age 29) and families of children living with a visual impairment.
• Guide Dogs supporting children and adults with sight loss with many services, both with and without dogs.
• Gene Vision A resource on rare genetic eye disorders for everyone