Ocular Involvement in Friedreich Ataxia Patients and its Relationship with Neurological Disability, a Follow-up Study

Abstract

: Background: This study compared functional and structural visual changes in Friedreich ataxia (FRDA) patients with healthy controls (HC) and correlated these changes with neurological disability.

Methods: Eight FRDA Spanish patients and eight HC were selected from 2014 to 2018. Best corrected visual acuity (BCVA), visual field (VF), optic coherence tomography (OCT), and neurological disability measured by "scale for the assessment and rating of ataxia" (SARA) were taken in a basal exploration and repeated after 6 months. A linear mixed analysis and Bonferroni p-value correction were performed.

Results: FRDA baseline and follow-up patients showed statistically significant decreases in BCVA, VF, and OCT parameters compared with the HC. Some of the VF measurements and most of the OCT parameters had an inverse mild-to-strong correlation with SARA. Moreover, the analysis of the ROC curve demonstrated that the peripapillary retinal nerve fiber layer (pRNFL) average thickness was the best parameter to discriminate between FRDA patients and HC.

Conclusions: The follow-up study showed a progression in OCT parameters. Findings showed a sequential effect in pRNFL, ganglion cell complex (GCC), and macula. The VF and the OCT could be useful biomarkers in FRDA, both for their correlation with neurological disease as well as for their ability to evaluate disease progression.

Keywords: FRDA; Friedreich ataxia; OCT; SARA; neurodegeneration; neurological disability; visual field.

Figure 1

Optic coherence tomography outcomes, follow-up study. Vertical axis in microns. (A) OCT pRNFL (peripapillary retinal nerve fiber layer) quadrants. Aver: average, Q: quadrants, S: superior, T: temporal, I: inferior, N: nasal. (B) OCT pRNFL horary sectors. H: clock-hour position. (C) OCT macula. CMT: central macular thickness. IMR: inner macular ring; OMR: outer macular ring; S: superior, T: temporal, N: nasal, I: inferior. (D) OCT GCC (ganglion cell complex). Sup: superior, Inf: inferior, T: temporal, N: nasal, Aver: average, Min: minimum.

Figure 2

ROC curve. (A) The average peripapillary retinal nerve fiber layer (pRNFL) thickness was the best parameter to discriminate between Friedreich ataxia (FRDA) patients and healthy controls (HC) with an area under the curve (AUC) of 0.984. (B) The cut-off point was 80.5 microns.