Eye health correlates with neurological disability in people with Friedreich’s ataxia (FA), a clinical study reports.
These findings support the potential of specific measures of vision and eye health to evaluate disease progression in this patient population, the scientists said.
The study “Ocular Involvement in Friedreich Ataxia Patients and Its Relationship with Neurological Disability, a Follow-Up Study” was published in the journal Diagnostics.
Problems with eyesight are frequent among people with FA. As many as 30% of all patients are estimated to have vision-related conditions, including optic neuropathy (damage to the optic nerve), and more rarely, retinitis pigmentosa-like syndrome.
Researchers in Spain investigated how functional and structural changes in FA patients’ vision are associated with the neurological disabilities that characterize the disease.
A clinical study (NCT03285204) included eight FA patients (mean age, 36) and eight healthy controls. The mean time from FA diagnosis was about 18.3 years. Both groups had neurological and visual measures assessed at the start of the study (baseline) and at follow-up six months later.
To evaluate neurological disability, researchers used the Scale for the Assessment and Rating of Ataxia (SARA), which ranges 0 (minimal disability) to 40 (maximum disability).
As expected, healthy individuals scored 0 both at baseline and follow-up. Among FA patients, neurological disability was a mean of 28.38 at baseline and 29.38 at six months.
Patients showed lower best-corrected visual acuity (a measure of eyesight) compared to controls. At baseline, FA patients had a score of 0.68 compared to 0.99 in controls, while at follow-up patients scored 0.63 and controls 0.98.
The team also evaluated the retina (the innermost, light-sensitive tissue layer of the eye) using a non-invasive technique called optic coherence tomography (OCT).
Differences between FA patients and controls in several parameters both at baseline and follow-up were reported. Lower values in patients correlated with higher SARA scores, meaning that a decline in vision measures was associated with greater neurological disability.
In particular, researchers found the thickness of the peripapillary retinal nerve fiber layer (pRNFL) — a measure of damage to the optic nerve — was the best parameter to distinguish patients from controls, as it was lower in those with FA. Its sensitivity was 100% and its specificity (the identification of true negatives) was 87.5%.
Within the FA group, pRNFL thickness was generally lower at follow-up, although in most cases these differences were not significant compared to baseline measures.
Lower scores in other measurements — including the visual field index that evaluates residual vision, and mean deviation that assesses sensitivity loss — were also associated with greater neurological disability.
“Visual field, and especially OCT, could be good biomarkers in [FA] patients, because of both their correlation with neurological disease as well as their ability to evaluate disease progression,” the researchers wrote.
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