Eye movement abnormalities may help detect, track FA progression
Over 80% of patients had same problems, suggesting they are 'core' changes
People with Friedreich’s ataxia often show abnormalities in their eye movements and looking for characteristic changes there may help diagnose the disease and track its progression, a review study finds.
“Quantitative oculomotor [eye movement] testing in [Friedreich’s ataxia] may facilitate early diagnosis and provide value in monitoring disease progression and treatment response,” the researchers wrote.
The study, “Oculomotor and Vestibular Deficits in Friedreich Ataxia – Systematic Review and Meta-Analysis of Quantitative Measurements,” was published in The Cerebellum.
Friedreich’s ataxia is a genetic disorder that mainly affects the muscles and the nervous system. It’s long been known that people with the disease may have eye movement abnormalities.
A trio of researchers in Switzerland and Australia reviewed the medical literature to describe what types of eye movement changes are most common in this disease and how they may be related to certain clinical aspects of Friedreich’s ataxia, such as its severity and duration. The review included data from 17 previously published studies of more than 180 patients.
Eye movement and FA disease severity, progression
The most common abnormalities included involuntary jerky side-to-side movements known as saccadic intrusions, issues with the eyes’ ability to follow movements, called pursuit, and abnormal angular vestibulo-ocular reflex (aVOR), which refers to the eyes’ ability to focus on one point while the head is moving.
Each of these abnormalities was seen in more than 80% of assessed patients, leading researchers to suggest they may be viewed as a “core” set of eye movement changes that are frequent in Friedreich’s ataxia and that may help identify the disease.
Patients with greater aVOR abnormalities also tended to report more severe motor symptoms and more issues with vision, analyses showed. These correlations suggest “alterations in aVOR parameters could provide insights into specific clinical manifestations,” the researchers wrote.
Disease severity also was associated with delays when performing visually guided saccades, that is, side-to-side eye movements elicited by having the patient look at two different targets.
Some data indicated patients who had square-wave jerks, a specific type of abnormal side-to-side eye movement, tended to see the onset of symptoms at an earlier age, but this finding wasn’t consistent from study to study, indicating further research was needed.
Many studies in the review used different methods to track eye movements, plus virtually all the studies assessed patients at a single point in time, so more research is needed to track how eye movement abnormalities change as the disease progresses, the researchers said.
“Future research in the field should prioritize standardized data collection methods and longitudinal observational studies to better understand [Friedreich’s ataxia] and its associated eye movement abnormalities,” they wrote.
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