Schepens Eye Research Institute of Mass Eye & Ear, Harvard Medical School, Department of Ophthalmology, Boston, Massachusetts, United States.
Invest Ophthalmol Vis Sci. 2024 Jul 1;65(8):46. doi: 10.1167/iovs.65.8.46.
The purpose of this study was to investigate gaze-scanning by pedestrians with homonymous hemianopia (HH) when walking on mid-block sidewalks.
Pedestrians with right homonymous hemianopia (RHH), and left homonymous hemianopia (LHH) without and with left spatial neglect (LHSN) walked on city streets wearing a gaze-tracking system. Gaze points were obtained by combining head movement and eye-in-head movement. Mixed-effects regression models were used to compare horizontal gaze scan magnitudes and rates between the side of the hemi-field loss (BlindSide) and the seeing side (SeeingSide), among the three subject groups, and between mid-block walking and street crossing segments.
A total of 7021 gaze scans were obtained from 341 minutes of mid-block walking videos by 19 participants (6 with LHH, 7 with RHH, and 6 with LHSN). The average gaze magnitude and scanning rate in mid-block segments were significantly higher towards the BlindSide than the SeeingSide in LHH (magnitude larger by 1.9° (degrees), P = 0.006; scan rate higher by 4.2 scans/minute, P < 0.001) and RHH subjects (magnitude larger by 3.3°, P < 0.001; scan rate higher by 3.2 scans/minute, P = 0.002), but they were not significantly different in LHSN subjects. The scanning rate, in terms of scans/minute (mean, 95% confidence interval [CI]) was significantly lower in LHSN subjects (mean = 6.9, 95% CI = 5.6-8.7) than LHH (mean = 10.2, 95% CI = 8.0-13.1; P = 0.03) and RHH (mean = 11.1, 95% CI = 9.0-13.7; P = 0.007) subjects. Compared to street-crossings, the scan rate during the mid-block segments was lower by 3.5 scans/minute (P < 0.001) and the gaze magnitude was smaller by 3.8° (P < 0.001) over the 3 groups.
Evidence of compensatory scanning suggests a proactive, top-down mechanism driving gaze in HH. The presence of spatial neglect (SN) appeared to negatively impact the top-down process.
本研究旨在探讨同侧偏盲（HH）患者在穿过街区人行道时的眼球扫视行为。
研究招募了右侧 HH（RHH）、左侧 HH（LHH）和左侧空间忽视（LHSN）患者，他们在穿戴眼动追踪系统的情况下于城市街道上行走。通过头部运动和眼内运动的组合来获取眼球注视点。使用混合效应回归模型比较了三组患者在穿过街区时对患侧（盲侧）和健侧（注视侧）的水平眼球扫视幅度和速率，以及在街区行走和街道穿行阶段的比较。
本研究共纳入了 19 名参与者的 341 分钟穿过街区的视频资料，获得了 7021 次眼球扫视数据。在 LHH 患者中，街区穿行阶段的眼球扫视幅度和速率在盲侧显著大于注视侧（扫视幅度大 1.9°，P = 0.006；扫视速率快 4.2 次/分钟，P < 0.001），在 RHH 患者中也呈现出相同的趋势（扫视幅度大 3.3°，P < 0.001；扫视速率快 3.2 次/分钟，P = 0.002），但在 LHSN 患者中差异无统计学意义。在 LHSN 患者中，以每分钟扫视次数（平均值，95%置信区间[CI]）表示的扫视速率明显低于 LHH 患者（平均值=6.9，95%CI=5.6-8.7）和 RHH 患者（平均值=11.1，95%CI=9.0-13.7；P = 0.03 和 P = 0.007）。与街道穿行阶段相比，三组患者在街区穿行阶段的扫视速率都显著减慢了 3.5 次/分钟（P < 0.001），眼球扫视幅度也都减小了 3.8°（P < 0.001）。
本研究结果表明，补偿性眼球扫视提示 HH 患者的眼球运动可能存在一种主动的、自上而下的机制。空间忽视的存在似乎对这种自上而下的过程产生负面影响。
