Abstract
BackgroundPatients with downbeat nystagmus syndrome suffer from oscillopsia, which leads to an unstable visual perception and therefore impaired visual acuity. The aim of this study was to use real-time computer-based visual feedback to compensate for the destabilizing slow phase eye movements.MethodsThe patients were sitting in front of a computer screen with the head fixed on a chin rest. The eye movements were recorded by an eye tracking system (EyeSeeCam®). We tested the visual acuity with a fixed Landolt C (static) and during real-time feedback driven condition (dynamic) in gaze straight ahead and (20°) sideward gaze. In the dynamic condition, the Landolt C moved according to the slow phase eye velocity of the downbeat nystagmus. The Shapiro-Wilk test was used to test for normal distribution and one-way ANOVA for comparison.ResultsTen patients with downbeat nystagmus were included in the study. Median age was 76 years and the median duration of symptoms was 6.3 years (SD +/- 3.1y). The mean slow phase velocity was moderate during gaze straight ahead (1.44°/s, SD +/- 1.18°/s) and increased significantly in sideward gaze (mean left 3.36°/s; right 3.58°/s). In gaze straight ahead, we found no difference between the static and feedback driven condition. In sideward gaze, visual acuity improved in five out of ten subjects during the feedback-driven condition (p = 0.043).ConclusionsThis study provides proof of concept that non-invasive real-time computer-based visual feedback compensates for the SPV in DBN. Therefore, real-time visual feedback may be a promising aid for patients suffering from oscillopsia and impaired text reading on screen. Recent technological advances in the area of virtual reality displays might soon render this approach feasible in fully mobile settings.
Highlights
Patients with downbeat nystagmus syndrome suffer from oscillopsia, which leads to an unstable visual perception and impaired visual acuity
Ten Patients with downbeat nystagmus syndrome (DBN) (4 male) with different etiologies were included in the study (cerebellar atrophy (n = 1), CANVAS (CANVAS = cerebellar ataxia, neuropathy, vestibular areflexia syndrome; n = 3), idiopathic (n = 6))
In order to compare both groups with inferential statistics, we first tested whether the assumption of normal distribution was fulfilled
Summary
Patients with downbeat nystagmus syndrome suffer from oscillopsia, which leads to an unstable visual perception and impaired visual acuity. Many patients with nystagmus (involuntary eye movements) suffer from blurred vision, unstable visual perception and decreased visual acuity (VA), which leads to a decreased quality of life. Patients predominantly suffer from balance disorders and oscillopsia. The latter results in a decrease of VA, in particular when looking downward during reading or to the DBN intensity can be reduced in slightly over 50 % of patients [4,5,6,7] by aminopyridines, but many patients do not respond to drug therapy. Patients may not tolerate the medical treatment or they still suffer from an impaired VA including text reading. There is reason to search for other treatment principles
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