Test-retest reliability of saccadic measures in subjects at-risk for Huntington disease
Tanya M. Blekher 1*,
Marjorie R Weaver 2,
Xueya Cai 3,
Siu Hui 3,
Jeanine D Marshall 2,
Jacqueline M Jackson 2,
Joanne M Wojcieszek 4,
Robert D. Yee 1,
and
Tatiana M Foroud 2
1 Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
2 Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana, United States
3 Medicine, Division of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, United States
4 Neurology, Indiana University School of Medicine, Indianapolis, Indiana, United States
* To whom correspondence should be addressed. E-mail: tblekher{at}iupui.edu.
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Abstract |
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Objective: Abnormalities in saccades appear to be sensitive and specific biomarkers in the prediagnostic stages of Huntington disease (HD). The goal of this study was to evaluate test-retest reliability of saccadic measures in prediagnostic carriers of the HD gene expansion (PDHD) and normal controls (NC).
Methods: The study sample included 9 PDHD and 12 NC who completed two study visits within an approximate one month time interval. At the first visit, all participants completed a uniform clinical evaluation. A high resolution video-based system was used to record eye movements during completion of a battery of visually guided, anti-saccade, and memory guided tasks. Latency, velocity, gain and percentage of errors were quantified. Test-retest reliability was estimated by calculating the intraclass correlation (ICC) of the saccade measures collected at the first and second visits. Additionally, an equality test based on Fisher's Z-transformation was used to evaluate the effects of group (PDHD and NC) and gender on ICC.
Results: Percentage of errors showed moderate to high reliability in the anti-saccade and memory guided tasks (ICC= 0.64- 0.93). Latency of the saccades also demonstrated moderate to high reliability (ICC= 0.55-0.89) across all tasks. The velocity and gain of the saccades showed moderate reliability. The ICC was similar in the PDHD and NC groups. There was no significant gender effect on the ICC.
Conclusions: Good reliability of saccadic latency and percentage of errors in both anti-saccade and memory guided tasks suggests that these measures could serve as potential biomarkers to evaluate progression in HD.
Key Words:
eye movements, saccadic eye movements, neuroophthalmology
