Machner Björn, Sprenger Andreas, Sander Thurid, Heide Wolfgang, Kimmig Hubert, Helmchen Christoph, Kömpf Detlef
Department of Neurology, University of Lübeck, Lübeck, Germamy.
Ann N Y Acad Sci. 2009 May;1164:419-26. doi: 10.1111/j.1749-6632.2009.03769.x.
Patients with homonymous hemianopia due to occipital brain lesions show disorders of visual search. In everyday life this leads to difficulties in reading and spatial orientation. It is a matter of debate whether these disorders are due to the brain lesion or rather reflect compensatory eye movement strategies developing over time. For the first time, eye movements of acute hemianopic patients (n= 9) were recorded during the first days following stroke while they performed an exploratory visual-search task. Compared to age-matched control subjects their search duration was prolonged due to increased fixations and refixations, that is, repeated scanning of previously searched locations. Saccadic amplitudes were smaller in patients. Right hemianopic patients were more impaired than left hemianopic patients. The number of fixations and refixations did not differ significantly between both hemifields in the patients. Follow-up of one patient revealed changes of visual search over 18 months. By using more structured scanpaths with fewer saccades his search duration decreased. Furthermore, he developed a more efficient eye-movement strategy by making larger but less frequent saccades toward his blind side. In summary, visual-search behavior of acute hemianopic patients differs from healthy control subjects and from chronic hemianopic patients. We conclude that abnormal visual search in acute hemianopic patients is related to the brain lesion. We provide some evidence for adaptive eye-movement strategies developed over time. These adaptive strategies make the visual search more efficient and may help to compensate for the persisting visual-field loss.
因枕叶脑损伤导致同侧偏盲的患者存在视觉搜索障碍。在日常生活中，这会导致阅读和空间定向困难。这些障碍是由于脑损伤所致，还是反映了随时间发展形成的代偿性眼球运动策略，目前仍存在争议。首次对9例急性偏盲患者在中风后的头几天进行眼球运动记录，当时他们正在执行一项探索性视觉搜索任务。与年龄匹配的对照受试者相比，由于注视和重新注视次数增加，即对先前搜索过的位置进行重复扫描，他们的搜索持续时间延长。患者的扫视幅度较小。右侧偏盲患者比左侧偏盲患者受损更严重。患者两眼半视野的注视和重新注视次数没有显著差异。对一名患者进行随访发现，其视觉搜索在18个月内发生了变化。通过使用更结构化的扫描路径且扫视次数减少，他的搜索持续时间缩短。此外，他通过向盲侧进行更大但频率更低的扫视，形成了更有效的眼球运动策略。总之，急性偏盲患者的视觉搜索行为不同于健康对照受试者和慢性偏盲患者。我们得出结论，急性偏盲患者的异常视觉搜索与脑损伤有关。我们为随时间发展形成的适应性眼球运动策略提供了一些证据。这些适应性策略使视觉搜索更有效，并可能有助于弥补持续存在的视野缺损。
