Infantile nystagmus

Nystagmus is a rhythmic, involuntary oscillation of one or both eyes.

The oscillation, rapid and repetitive, takes place in two phases that lead the eyes to look away and then back towards the object in focus.

Nystagmus may be horizontal, vertical or torsional (i.e. circular) or it may be non-specific (i.e. with an undefined direction).

The other characteristics of nystagmus are the frequency of eye movement (low, high and moderate), which indicates the number of shakes in the unit of time - and the amplitude of the shake movement (fine, medium and wide).

It may involve one eye (monocular nystagmus) or both eyes (binocular nystagmus); it is called 'conjugate' when the direction, frequency and amplitude of the oscillations are similar in both eyes, otherwise it is called 'dissociated'.

It can also be classified as 'pendular', when there is a constant oscillation between the two extremes of movement, or 'jerky' when it is characterised by a slow phase and a rapid phase.

It is an overall rather rare pathological condition, affecting on average 14 to 6.1 children per 10,000 live births, with a higher prevalence in premature infants.

Nystagmus can be classified into 'congenital', when it first appears within the first six months of life, and 'acquired', if it occurs later. It is defined as 'idiopathic' when the cause cannot be identified.

Through genetic mapping, a number of genes have been identified whose mutations may cause nystagmus, in particular mutations in the FRMD7 gene appear to underlie hereditary nystagmus. In most cases of acquired nystagmus, on the other hand, the origin is often due to concomitant neurological pathologies or lesions of the nervous system (cerebellum and brainstem) or the vestibular apparatus (which controls balance).

Children with nystagmus must be treated specifically in relation to the specific aetiology of the form from which they suffer

A study recently published in Eye, Nystagmus in infancy: causes, characteristics and main tools for diagnosis, thoroughly investigated the causal factors, clinical features and main diagnostic tools used to investigate childhood nystagmus. The retrospective study enrolled 147 children, aged between 0 and 1 year, whose clinical examinations, genetic tests and electroretinograms (ERG) were considered.

The most important results of this study indicate that albinism and hereditary retinal diseases are the most common causes of congenital nystagmus. Albinism was found to be the cause responsible for 59.2% of all cases, while hereditary retinal diseases were the predominant cause in 19.5% of the children examined. Albinism was diagnosed most often in children under 6 months of age, while hereditary retinal diseases were identified predominantly in older children within the patient cohort.

The researchers point out that to arrive at the final diagnosis, a comprehensive eye examination for albinism is the test of choice, while ERG in combination with genetic testing is indicated to diagnose nystagmus in children with inherited retinal diseases.

An important finding is that vertical nystagmus, which is considered to be due to neurological causes in articles published in the literature, is frequently associated with hereditary retinal diseases in the cohort of young patients examined.

Finally, magnetic resonance imaging (MRI) of the head, which is one of the most widely used tests in children with nystagmus, actually appears to have low diagnostic potential in the specific age group of children observed in this study.

On the subject of paediatric ophthalmology see also:

• Dysgraphia and visuo-postural defects - Oculist Italiano
• Retinoblastoma update - Oculista Italiano
• Paediatric vision screening - Oculista Italiano

• Goldman, E., Hendler, K. & Yahalom, C. Nystagmus in infancy: causes, characteristics and main tools for diagnosis. Eye(2024). https://doi.org/10.1038/s41433-024-03504-4
• Hvid K, Nissen KR, Bayat A, Roos L, Grønskov K, Kessel L. Prevalence and causes of infantile nystagmus in a large population-based Danish cohort. Acta Ophthalmol. 2020;98:506-13
• Self JE, Dunn MJ, Erichsen JT, Gottlob I, Griffiths HJ, Harris C, et al. Management of nystagmus in children: a review of the literature and current practice in UK specialist services. Eye. 2020;34:1515-34.