Causes of the condition nystagmus in very young patients can be challenging to isolate due to limited cooperation in preverbal kids, variability in presentation and the possibility of many etiologies. In infancy, nystagmus may be present as part of an ocular condition, a neurological disorder or could be idiopathic. Because of these variable causes, comprehensive diagnostic approach embodies discretionary testing based on clinical characteristics.

Retinal dystrophy, the second most common cause of nystagmus in this study, was more difficult to identify in the child’s first six months of life due to the immaturity of the developing retina. Photo: Goldman E, et al. Eye (Lond). December 5, 2024. Click image to enlarge.

Consequently, researchers wanted to investigate the main causes for nystagmus in infants up to one year of age as well as the accompanying clinical signs and efficacy of differing diagnostic tests. The retrospective study used medical records from 147 infants seen at a tertiary hospital. Collected data included age at presentation, strabismus presence, refractive errors, auxiliary tests performed to reach diagnosis and initial vs. final diagnosis. 

The study authors found that the most common ocular pathology causing nystagmus was albinism, followed by inherited retinal diseases (IRDs). The main test that helped reach diagnosis for albinism was clinical ophthalmologic examination for albinism and electroretinogram together with genetic testing for IRDs. Vertical nystagmus was only seen in eight infants; of these, four had an IRD at final diagnosis. The most common associated clinical characteristics were high hypermetropia and strabismus.

In the discussion section of their paper for the British journal Eye, the authors emphasize that albinism was the predominant cause of nystagmus in this group, accounting for over half of cases. Although most often this is clinically diagnosed without further testing, they do note that they identified 8.2% (n=12) patients whose final diagnosis changed from idiopathic nystagmus to albinism.

IRDs were the second most common cause and, as with albinism, represented 24 cases that initially were diagnosed as idiopathic nystagmus only to have final diagnosis changed after electroretinography and genetic testing. The authors stress that IRDs play an important role in causation during infancy and can often be missed during first months of life. It should be noted that vertical nystagmus was also commonly observed in this group.

As the authors add in their paper, “this underscores the critical role of thorough clinical evaluation” as well as “the necessity of additional testing in determining the etiology of nystagmus, particularly in IRDs.”

Diagnoses associated with albinism or IRD were reached predominantly before six months of age; however, there was also a slight increase in prevalence of IRD diagnosis after six months. “We suggest that this increase indicates that its clinical signs, even though they appear during the first months of life, are still subtle, thus delaying the diagnosis,” the authors wrote. As well, lack of retinal maturity before six months could also cause delays in performing electroretinography tests that could aid this diagnosis.

Finally, the authors bring attention to the paradigm that vertical nystagmus has been primarily linked to neurological origins, but with more recent literature finding vertical forms not exclusively implying neurological basis, instead also manifesting in cases of IRD, albinism and idiopathic nystagmus. All cases in this study with neurological causes exhibited horizontal waveform pattern, with none of the vertical cases with a neurological cause. Also, because of the 50% of vertical cases found as result of IRDs, the authors prompt that “these findings underscore the notion that vertical nystagmus patterns may suggest a neurological cause but do not exclude ocular etiologies, particularly IRDs. Therefore, it is crucial to consider and investigate these potential etiologies alongside neurological ones.”