Papageorgiou Eleni, Hardiess Gregor, Mallot Hanspeter A, Schiefer Ulrich
Center for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Germany.
Vision Res. 2012 Jul 15;65:25-37. doi: 10.1016/j.visres.2012.06.004. Epub 2012 Jun 18.
Aim of the present study was to identify efficient compensatory gaze patterns applied by patients with homonymous visual field defects (HVFDs) under virtual reality (VR) conditions in a dynamic collision avoidance task. Thirty patients with HVFDs due to vascular brain lesions and 30 normal subjects performed a collision avoidance task with moving objects at an intersection under two difficulty levels. Based on their performance (i.e. the number of collisions), patients were assigned to either an "adequate" (HVFD(A)) or "inadequate" (HVFD(I)) subgroup by the median split method. Eye and head tracking data were available for 14 patients and 19 normal subjects. Saccades, fixations, mean number of gaze shifts, scanpath length and the mean gaze eccentricity, were compared between HVFD(A), HVFD(I) patients and normal subjects. For both difficulty levels, the gaze patterns of HVFD(A) patients (N=5) compared to HVFD(I) patients (N=9) were characterized by longer saccadic amplitudes towards both the affected and the intact side, larger mean gaze eccentricity, more gaze shifts, longer scanpaths and more fixations on vehicles but fewer fixations on the intersection. Both patient groups displayed more fixations in the affected compared to the intact hemifield. Fixation number, fixation duration, scanpath length, and number of gaze shifts were similar between HVFD(A) patients and normal subjects. Patients with HVFDs who adapt successfully to their visual deficit, display distinct gaze patterns characterized by increased exploratory eye and head movements, particularly towards moving objects of interest on their blind side. In the context of a dynamic environment, efficient compensation in patients with HVFDs is possible by means of gaze scanning. This strategy allows continuous update of the moving objects' spatial location and selection of the task-relevant ones, which will be represented in visual working memory.
本研究的目的是确定在虚拟现实（VR）条件下，患有同向性视野缺损（HVFDs）的患者在动态避撞任务中所采用的有效代偿性注视模式。30例因脑血管病变导致HVFDs的患者和30名正常受试者在两个难度级别下，对交叉路口处移动的物体执行避撞任务。根据他们的表现（即碰撞次数），通过中位数分割法将患者分为“充分”（HVFD(A)）或“不充分”（HVFD(I)）亚组。14例患者和19名正常受试者有眼动和头部追踪数据。比较了HVFD(A)组、HVFD(I)组患者和正常受试者之间的扫视、注视、平均注视转移次数、扫描路径长度和平均注视离心率。对于两个难度级别，与HVFD(I)组患者（N = 9）相比，HVFD(A)组患者（N = 5）的注视模式表现为向患侧和健侧的扫视幅度更长、平均注视离心率更大、注视转移更多、扫描路径更长，且对车辆的注视更多，但对交叉路口的注视更少。与健侧半视野相比，两组患者在患侧半视野的注视都更多。HVFD(A)组患者和正常受试者之间的注视次数、注视持续时间、扫描路径长度和注视转移次数相似。成功适应视觉缺陷的HVFDs患者表现出独特的注视模式，其特征是眼球和头部的探索性运动增加，尤其是朝向其盲侧感兴趣的移动物体。在动态环境中，HVFDs患者通过注视扫描有可能实现有效的代偿。这种策略允许不断更新移动物体的空间位置，并选择与任务相关的物体，这些物体将在视觉工作记忆中得到表征。
