Objectives: To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.
Methods: Typical cases of visual field defects caused by injuries to the optic chiasm, optic tracts, optic radiations, and visual cortex were selected. Visual field examinations, visual evoked potential (VEP) and multifocal visual evolved potential (mfVEP) measurements, craniocerebral CT/MRI, and retinal optical coherence tomography (OCT) were performed, respectively, and the aforementioned visual electrophysiological and neuroimaging indicators were analyzed comprehensively.
Results: The electrophysiological manifestations of visual field defects caused by optic chiasm injuries were bitemporal hemianopsia mfVEP abnormalities. The visual field defects caused by optic tract, optic radiation, and visual cortex injuries were all manifested homonymous hemianopsia mfVEP abnormalities contralateral to the lesion. Mild relative afferent pupil disorder (RAPD) and characteristic optic nerve atrophy were observed in hemianopsia patients with optic tract injuries, but not in patients with optic radiation or visual cortex injuries. Neuroimaging could provide morphological evidence of damages to the optic chiasm and its posterior visual pathway.
Conclusions: Visual field defects caused by optic chiasm, optic tract, optic radiation, and visual cortex injuries have their respective characteristics. The combined application of mfVEP and static visual field measurements, in combination with neuroimaging, can maximize the assessment of the location and degree of visual pathway damage, providing an effective scheme for the identification of such injuries.
目的: 探讨视交叉及其后部视路损伤所致视野缺损的特点及其客观评定方法。方法: 选择视交叉、视束、视放射及视皮质损伤所致视野缺损典型案例，分别进行视野、视觉诱发电位（visual evoked potential，VEP）、多焦视觉诱发电位（multifocal visual evoked potential，mfVEP）检查以及颅脑CT或MRI、视网膜光学相干断层扫描（optical coherence tomography，OCT），并对上述视觉电生理指标及神经影像学指标进行综合分析。结果: 视交叉损伤所致视野缺损的电生理学表现为双颞侧偏盲型mfVEP异常；视束、视放射及视皮质损伤所致视野缺损均表现为病变对侧的同向性偏盲型mfVEP异常。视束损伤出现偏盲眼轻度相对性传入性瞳孔障碍（relative afferent pupil disorder，RAPD）及特征性视神经萎缩表现，视放射、视皮质损伤则无此表现。神经影像学可为视交叉及其后部视路损伤提供形态学证据。结论: 视交叉、视束、视放射及视皮质损伤所致视野缺损具有各自特点，通过mfVEP视野与静态视野检查的联合应用，结合神经影像学检查，可最大程度地评价视路受损的部位和程度，为此类损伤的认定提供有效方案。.
Keywords: field of view; forensic medicine; multifocal visual evoked potential (mfVEP); optic chiasma; optic nerve injury; visual electrophysiology; visual pathway; wounds and injuries.