Abstract
Ocular abnormalities occur frequently in Friedreich’s ataxia (FRDA), although visual symptoms are not always reported. We evaluated a cohort of patients with FRDA to characterise the clinical phenotype and optic nerve findings as detected with optical coherence tomography (OCT). A total of 48 patients from 42 unrelated families were recruited. Mean age at onset was 13.8 years (range 4–40), mean disease duration 19.5 years (range 5–43), mean disease severity as quantified with the Scale for the Assessment and Rating of Ataxia 22/40 (range 4.5–38). All patients displayed variable ataxia and two-thirds had ocular abnormalities. Statistically significant thinning of average retinal nerve fibre layer (RNFL) and thinning in all but the temporal quadrant compared to controls was demonstrated on OCT. Significant RNFL and macular thinning was documented over time in 20 individuals. Disease severity and visual acuity were correlated with RNFL and macular thickness, but no association was found with disease duration. Our results highlight that FDRA is associated with subclinical optic neuropathy. This is the largest longitudinal study of OCT findings in FRDA to date, demonstrating progressive RNFL thickness decline, suggesting that RNFL thickness as measured by OCT has the potential to become a quantifiable biomarker for the evaluation of disease progression in FRDA.
Highlights
Friedreich’s ataxia (FRDA) is the most frequent autosomal recessive (AR) inherited ataxia [1,2], caused by a defect in the frataxin (FXN) gene on chromosome 9 (9q13q21.1,57) [3]
A handful of studies evaluated peripapillary retinal nerve fibre layer (RNFL) changes using optical coherence tomography (OCT) [18,19,20,21,22] and reported decreased average RNFL thickness [20], which was statistically significant in comparison to controls [18,19,21,22]
Tomography 2021, 7, FOR PEER REVIEW The age-at-symptom-onset ranged between 4–40 years, while disease7 duration varied between 5–43 years
Summary
Friedreich’s ataxia (FRDA) is the most frequent autosomal recessive (AR) inherited ataxia [1,2], caused by a defect in the frataxin (FXN) gene on chromosome 9 (9q13q21.1,57) [3]. Nystagmus is less common but still frequent, and other abnormalities include ocular flutter, saccadic dysmetria, disrupted pursuits and symptomatic oscillopsia [8,10,13,15,17]. Primarily descriptive studies of the afferent visual system in FRDA reported optic disc pallor on fundus examination, documented in 30% of affected individuals [10]. A handful of studies evaluated peripapillary retinal nerve fibre layer (RNFL) changes using optical coherence tomography (OCT) [18,19,20,21,22] and reported decreased average RNFL thickness [20], which was statistically significant in comparison to controls [18,19,21,22]. FRDA was reported to be associated with the greatest degree of RNFL thinning in comparison to a range of other genetically characterised ataxias [23]
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