A simple saccadic reading test to assess ocular motor function in cerebellar ataxia

Abstract

Cerebellar ataxia is a neurological disorder due to dysfunction of the cerebellum that affects coordination of fine movement, gait, and balance. Although ataxic patients commonly exhibit abnormal eye movement and have difficulties with saccadic reading, quantification of ocular motor abilities during reading in the clinical setting is rarely done. In this study, we assess visual performance with simple reading tests that can be used in the clinical setting and performed video infrared oculography in 11 patients with hereditary or acquired cerebellar ataxia and 11 age-matched controls. We found that compared with controls, ataxic patients read significantly slower on regularly and irregularly spaced 120 single-digit number reading tasks (read aloud) (p = 0.02 for both) but not on a word reading task (read silently), although there was large variability on the word reading task. Among the 3 reading tasks, the regularly spaced number reading task had the greatest difference (44%) between ataxic patients and controls. Analysis of oculography revealed that ataxic patients had slower reading speeds on the regularly spaced number reading task because of significantly higher saccade and fixation counts, impairment of small amplitude progressive saccades as well as large amplitude, line-changing saccades, greater fixation dispersion, and irregularity of scan paths and staircase gaze patterns. Our findings show that infrared oculography remains the gold standard in assessment of ocular motor difficulties during reading in ataxic patients. In the absence of this capability in the clinical setting, a simple 120 regularly spaced single-digit saccadic number reading test, which most patients can perform in less than 2 minutes, can be a possible biomarker for ocular motor abilities necessary for reading.

Quantitative Oculomotor Assessment in Hereditary Ataxia: Systematic Review and Consensus by the Ataxia Global Initiative Working Group on Digital-motor Biomarkers

“…While the dynamic visual acuity provides a functional assessment of the integrity of the rotational vestibulo-ocular reflex, this paradigm has been considered in a single study only in our literature review [ 52 ]. Other potentially suitable measures include assessments of visual stability, i.e., the amount of visual impairment by fixation instability as, e.g., SN, GEN, and SI or reading performance [ 53 ]. Future validation studies of quantitative oculomotor parameters in hereditary ataxia must include such clinician-reported or patient-reported outcome measures of oculomotor function to effectively aim for trial readiness.…”

Reading in Children Who Survived Cerebellar Tumors: Evidence from Eye Movements

“…We observed a large number of non-significant fixations during reading tasks, which were excluded from the analysis at the preprocessing stage. These abnormalities lead to more frequent and abnormal saccades and fixations during reading as well as other visual tasks [ 44 ], while healthy children executed effective eye movements, thus reducing performance time for both searching and reading tasks. Correlation between performance time for searching task and reading efficiency underline their similarity.…”

Normative Values of the Groffman Visual Tracing Test for the Assessment of Oculomotor Performance in the Adult Population

“…Oculomotor deficits can be found in patients who have suffered a stroke at a high percentage, ranging from 7% to 86% [18][19][20][21], depending on specific deficits, the time elapsed since the stroke, and the stage of recovery. In particular, oculomotor problems have been observed in association with specific cognitive deficits such as unilateral spatial neglect [22,23], neglect dyslexia [24,25], simultanagnosia [26], oculomotor apraxia [27], Balint syndrome [28], progressive supranuclear palsy (PSP) [29], and cerebellar ataxia [30].…”