Ramaioli Cecilia, Colagiorgio Paolo, Sağlam Murat, Heuser Fabian, Schneider Erich, Ramat Stefano, Lehnen Nadine
German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany; Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy.
Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy.
PLoS One. 2014 Oct 20;9(10):e110322. doi: 10.1371/journal.pone.0110322. eCollection 2014.
Patients with bilateral vestibular dysfunction cannot fully compensate passive head rotations with eye movements, and experience disturbing oscillopsia. To compensate for the deficient vestibulo-ocular reflex (VOR), they have to rely on re-fixation saccades. Some can trigger "covert" saccades while the head still moves; others only initiate saccades afterwards. Due to their shorter latency, it has been hypothesized that covert saccades are particularly beneficial to improve dynamic visual acuity, reducing oscillopsia. Here, we investigate the combined effect of covert saccades and the VOR on clear vision, using the Head Impulse Testing Device-Functional Test (HITD-FT), which quantifies reading ability during passive high-acceleration head movements. To reversibly decrease VOR function, fourteen healthy men (median age 26 years, range 21-31) were continuously administrated the opioid remifentanil intravenously (0.15 µg/kg/min). VOR gain was assessed with the video head-impulse test, functional performance (i.e. reading) with the HITD-FT. Before opioid application, VOR and dynamic reading were intact (head-impulse gain: 0.87±0.08, mean±SD; HITD-FT rate of correct answers: 90±9%). Remifentanil induced impairment in dynamic reading (HITD-FT 26±15%) in 12/14 subjects, with transient bilateral vestibular dysfunction (head-impulse gain 0.63±0.19). HITD-FT score correlated with head-impulse gain (R = 0.63, p = 0.03) and with gain difference (before/with remifentanil, R = -0.64, p = 0.02). One subject had a non-pathological head-impulse gain (0.82±0.03) and a high HITD-FT score (92%). One subject triggered covert saccades in 60% of the head movements and could read during passive head movements (HITD-FT 93%) despite a pathological head-impulse gain (0.59±0.03) whereas none of the 12 subjects without covert saccades reached such high performance. In summary, early catch-up saccades may improve dynamic visual function. HITD-FT is an appropriate method to assess the combined gaze stabilization effect of both VOR and covert saccades (overall dynamic vision), e.g., to document performance and progress during vestibular rehabilitation.
双侧前庭功能障碍患者无法通过眼球运动完全补偿被动头部旋转，因而会经历令人不适的视振荡。为了补偿不足的前庭眼反射（VOR），他们不得不依赖重新注视扫视。有些人在头部仍在移动时能触发“隐蔽”扫视；另一些人则仅在之后才开始扫视。由于其潜伏期较短，有人推测隐蔽扫视对提高动态视力、减少视振荡特别有益。在此，我们使用头部脉冲测试装置-功能测试（HITD-FT）来研究隐蔽扫视和VOR对清晰视觉的联合作用，该装置可量化被动高加速头部运动期间的阅读能力。为了可逆地降低VOR功能，对14名健康男性（年龄中位数26岁，范围21 - 31岁）持续静脉注射阿片类药物瑞芬太尼（0.15 µg/kg/min）。通过视频头部脉冲测试评估VOR增益，用HITD-FT评估功能表现（即阅读）。在应用阿片类药物之前，VOR和动态阅读功能正常（头部脉冲增益：0.87±0.08，平均值±标准差；HITD-FT正确答案率：90±9%）。瑞芬太尼导致12/14名受试者的动态阅读功能受损（HITD-FT为26±15%），伴有短暂的双侧前庭功能障碍（头部脉冲增益0.63±0.19）。HITD-FT评分与头部脉冲增益相关（R = 0.63，p = 0.03），也与增益差异相关（用药前/用药后，R = -0.64，p = 0.02）。一名受试者头部脉冲增益正常（0.82±0.03）且HITD-FT评分较高（92%）。一名受试者在60%的头部运动中触发隐蔽扫视，尽管头部脉冲增益异常（0.59±0.03），但在被动头部运动期间仍能阅读（HITD-FT为93%），而12名没有隐蔽扫视的受试者中没有一人能达到如此高的表现。总之，早期的追赶扫视可能会改善动态视觉功能。HITD-FT是评估VOR和隐蔽扫视联合注视稳定作用（总体动态视觉）的合适方法，例如，用于记录前庭康复期间的表现和进展。
