Childhood Nystagmus: for patients

• Overview
• The condition
• Treatment
• Current research
• Practical advice
• Referral to a specialist centre
• Further information and support
• A patient’s perspective
• References

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Overview

Our eyes are controlled by 6 muscles located around the eyes. These muscles work together to allow smooth movements so that the brain can see the world around us. The muscles around the eyes are controlled by the brain through electrical signals and sometimes these signals can be interrupted from a young age. This can cause involuntary movements of the eyes, called nystagmus. Nystagmus that presents within the first 6 months of life is called infantile/childhood nystagmus, which can be associated with certain eye conditions such as albinism, congenital cataracts and inherited retinal dystrophies. Sometimes, it can also occur even if there are no abnormalities of the eyes or brain. This is termed Infantile Idiopathic Nystagmus (IIN).

In general, the involuntary eye movements move horizontally, but they can also move vertically and rotationally. Childhood nystagmus occurs in about 19 per 10,000 babies.^[1] This figure can vary in nystagmus due to other eye conditions. Nystagmus can impact the visual world of children in different ways. They usually have blurred vision but DO NOT see the world moving. In some cases, nystagmus can be associated with a “lazy eye” and reduced depth perception, this can lead to the inability to recognise faces. In some cases of nystagmus that are associated with Albinism, children can be sensitive to bright lights.

Sometimes, children will use a compensatory head posture to help them see better. In cases where severe head postures are adopted which can lead to discomfort in the neck, shoulder and upper back, surgery can be undertaken to reposition the eyes so that the gaze of vision is centred.

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The condition

Symptoms

1) Abnormal visual behaviour

Apart from nystagmus, some children display features that may alert parents and healthcare workers that eyes are not working as well as expected:

• Strabismus/squint (abnormal alignment of the eyes when looking at an object)
• The child may not be responding to visual stimuli such as lights, faces or toys

2) Amblyopia (“lazy eye”)

When a baby is born, their eyes and brain work together to build a visual pathway that allows the brain to process visual information collected from the eyes. Most of the visual pathway develops up to the age of 8 years though further changes can be observed into adulthood.^[2] For this pathway to develop normally, the eyes need to constantly send clear images to stimulate the brain. Any malfunction of the structures along this pathway will result in amblyopia. Vision in the “lazy eye” may be permanently reduced if not detected and treated in time.

Nystagmus can cause blurry vision and issues with depth perception but the severity varies from child to child. In addition, some children may have an associated squint or difficulty focusing an image (requiring glasses to correct), which contributes to amblyopia development. It is important to note that visual function does not tend to deteriorate over time.

3) Abnormal head posture

Some children may adopt a compensatory head posture to optimise their vision. The adopted head position is usually where the eye movements are at their slowest and finest (medically known as the null point). The head postures vary among patients.

4) Symptoms from other conditions

Childhood nystagmus can be a manifestation of a number of conditions affecting the eye and/or other parts of the body. As a result, children may experience other symptoms as well in addition to nystagmus. Examples include:

• Albinism
• Aniridia
• Retinopathy of prematurity
• Inherited retinal dystrophies (e.g. Leber congenital amaurosis, Alstrom syndrome etc)
• Ocular coloboma
• Congenital cataract
• Optic disc atrophy
• Optic nerve hypoplasia
• Down syndrome
• Cerebral palsy

Cause

Childhood nystagmus can be caused by problems in the eyes or parts of the brain that control eye movements. In some children, it is an isolated eye condition where no abnormalities of the eye or brain are identified. Such cases are termed Infantile Idiopathic Nystagmus (IIN).

Two genes (FRMD7 and GPR143) have been identified so far that cause IIN. Scientists are working on finding the other causal genes by screening certain locations in the chromosome that are likely to be associated with IIN.

In cases where there is an association with conditions affecting the eye and/or other parts of the body, a number of genes have been identified depending on the condition.

How is it diagnosed?

All babies in the UK are screened for eye and other physical problems in the first 72 hours after birth as part of the newborn screening programme. Babies are then checked again between 6 and 8 weeks of age. Nystagmus can be detected during these examinations and babies are referred to an ophthalmologist for further assessment.

During the clinic appointment, eye drops that dilate the pupils are applied so that the eye professional can test whether glasses are required and also examine the health of the retina and optic disc. In addition, the ophthalmologist will also request further tests such as using a specialised camera called optical coherence tomography (OCT) to visualise the macula in more detail and performing electro-diagnostic tests called visual evoked potentials (VEP) and electroretinogram (ERG). VEP and ERG are non-invasive tests used to assess the function of the optic nerve and the retina respectively.  These tests are performed routinely for children presenting with nystagmus.

Sometimes, the ophthalmologist may also want to examine the parents as well even though they may be unaware of any visual problems. This is because either parent may have a very mild condition which does not affect his/her vision.

Genetic testing can be undertaken to help identify the gene(s) responsible so that families can have a more informed genetic counselling session.

If there is evidence suggesting other parts of the body may be affected, the child will be referred to a paediatrician for further evaluation which may include:

• General physical examination
• Developmental assessment
• Blood tests
• MRI (magnetic resonance imaging) of the brain

This is not an exhaustive list and other tests may be requested depending on the examination findings.

How is it inherited?

1) X-linked inheritance

The genetic changes causing Infantile Idiopathic Nystagmus is usually inherited in this manner. This means that the faulty gene is located on the X chromosome (determines our gender together with the Y chromosome). Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.

As a result, males are usually affected in conditions inherited in an X-linked manner as they only have one X-chromosome containing the faulty gene copy. On the other hand, some cells in females contain the second functioning X chromosome and thus do not display any symptoms (heterozygous carrier).

If the mother is a carrier and the father is healthy:

• Each son has a 50% chance of being affected
• Each daughter has a 50% chance of being a carrier like the mother

If the father is affected and the mother is healthy:

• None of his sons will be affected
• All of his daughters will be carriers

2) Autosomal dominant inheritance

Less commonly, IIN is inherited in this manner. This means that only one copy of the faulty gene (inherited from either parent) is required to cause disease. As a result, each new-born of the affected individual has a 50% chance of inheriting the condition regardless of gender.

If you or your child is affected by nystagmus that may be due to a genetic cause, families may choose to see a genetic counsellor to obtain more information and advice on inheritance and family planning options.

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Treatment

Is there any treatment?

The treatment for nystagmus can vary, firstly investigations need to be undertaken to determine whether the case is IIN or associated with another eye or systemic condition. In general, a patient with nystagmus may have the following treatments:

• Glasses/ contact lenses – to help sharpen the vision
• Eye drops – to help reduce the eye movement
• Occlusion therapy– The stronger eye is usually patched for several hours every day so that the weaker eye can be stimulated
• Wearing caps or hats with a wide brim which may help with sensitivity to light (if present)

Treatment with medications such as gabapentin or memantine have been shown to improve vision by reducing the extent of nystagmus^[3,4], but data of their usage in children is lacking.^[5]

Does my child require surgery?

Not in many cases. Surgery is usually only undertaken if a child is adopting an extreme head posture to optimise vision as this can lead to severe discomfort in the neck, shoulder and upper back. These issues may cause problems later on with posture if not addressed. Surgery does not correct the nystagmus but aims to re-align the position of the gaze so that the child is at a more comfortable position to make use of the null point. The procedure is done under general anaesthesia, which means the child will be unconscious during the operation.

What are the possible complications after surgery?

The following complications may occur after surgery:

• Double vision (diplopia)
• Eye infection (rare)
• Further corrections of the gaze may occasionally be required

Other considerations

If nystagmus is due to a condition that affects other parts of the body, a paediatrician is usually involved in the care of the child along with other relevant specialists.

Furthermore, visual impairment can have a negative impact on a child’s early general development.Therefore, timely referral to practitioners familiar with developmental surveillance and intervention for children with visual impairment (VI), such as developmental paediatricians as well as a Qualified Teacher of children and young people with Visual Impairment (QTVI) is crucial to optimise their developmental potential.

The Developmental Journal for babies and young children with visual impairment (DJVI), developed by Great Ormond Street Hospital Developmental Vision team is a structured early intervention programme designed to track developmental and vision progress in children from birth to three years of age. It is mainly used by qualified healthcare professionals working in services providing support to babies and young children with VI in conjunction with the child’s parents. Children with VI may be referred to specialist services such as the developmental vision clinic in the Great Ormond Street Hospital for Children or other specialist developmental services for further management.

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Current research in nystagmus

Research is currently being undertaken into the diagnosis and treatment of nystagmus. These treatments include the use of glasses^[6-8], oral medications, eyedrops^[3,4]and surgery^[9-11] to improve vision.

A clinical trial (NCT 04142307) is currently ongoing in Toronto investigating whether a technique called biofeedback training can help improve eye movement control and therefore vision in patients with Infantile Idiopathic Nystagmus.

Related links

• Research Opportunities at Moorfields Eye Hospital UK
• Searching for current clinical research or trials

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Practical advice

Living with nystagmus

The visual function of patients is highly variable but the majority still have some degree of reduced vision into adulthood. However, they are still able to lead a relatively independent life through maximising their available vision and having access to social support. Here are some ideas:

• Attending the low vision clinic which provides access to low vision specialists, Eye Clinic Liaison Officers (ECLOs) and visual aids
• Utilising assistive technologies that can improve quality of life
• Noticing your child’s preferential head position when looking at objects can help you to understand where you should hold toys or position yourself as this is often where your child finds to have the best vision (the null point)
• Getting in touch with the local education authority for access to qualified teachers for children with visual impairment (QTVI) and special educational needs co-ordinator (SENCO)
• Registering your child as sight impaired (SI) or severely sight impaired (SSI) if eligible for access to social support and financial concessions
• Getting in touch with national or local charities for advice and peer support

Related links

• Coping with sight loss
• Education and learning
• Employment support
• Family support service
• Driving and alternative transport

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Referral to a specialist centre

If you are based in the UK and would like to be seen in the nearest specialist centre for your eye condition, either to receive a more comprehensive genetic management or just to find out more about current research, you can approach your GP to make a referral or alternatively arrange for a private appointment. 

More information can be found in our “How to see a genetic eye specialist?” page.

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Further information and support

• Nystagmus Network
• Albinism Fellowship
• Royal National Institute of Blind People (RNIB)
• IN-vision

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A patient’s perspective

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References

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