藍光對動態視力的影響

Abstract

動態視力對於動物狩獵及人類生活都是不可或缺的重要能力，但目前關於如何增進動態視力的知識有限。先前研究已知藍光可能透過自發性感光視網膜神經節細胞(intrinsically photosensitive retinal ganglion cells, ipRGCs)增進人類的警醒能力，動物研究也發現ipRGCs對運動知覺敏感，因此推論藍光能影響與運動知覺有關的動態視力。本研究透過五個實驗探討藍光是否能增進人類的動態視力。動態視力共分成三項能力指標來檢視：眼動追蹤(eye pursuit accuracy, EPA，實驗一)、前後移動的立體動體視力(kinetic visual acuity, KVA，實驗一、二)、與水平上下左右移動的平面動體視力(dynamic visual acuity, DVA，實驗三到五)。EPA能力由眼動追蹤時的凝視點與目標物間距離計算而得；KVA是讓受試者在具有深度空間感的螢幕上觀看往前移的三個數字，並以階梯法測量速度敏感度；DVA則為在同一平面上出現三個數字，並操弄不同方向(實驗三)、不同困難度(實驗四)、以及透過操弄ipRGC刺激量的藍光濾鏡測量是否為ipRGCs的貢獻。結果顯示藍光的確能夠增進EPA，KVA則是在藍光下表現較差，而DVA的藍光增進效果只出現在實驗三的向下運動以及實驗四的低對比度等困難作業的情況。此增進效果並非來自於ipRGCs的機制，至少在如實驗五的設備下無法被證實。本研究首次探討了藍光對於不同動態視力三種指標的影響，並發現藍光能夠在困難作業下增進動體視力中DVA的敏感度。

Dynamic vision is crucial to not only animals’ hunting but also human activities, and yet little is known about how to enhance it, except for extensive training like athletics do. Exposure to blue light has been shown to enhance human alertness, perhaps through intrinsically photosensitive retinal ganglion cells (ipRGCs), which are sensitive to motion perception as revealed by animal studies. However, it remains unknown whether blue light can enhance human dynamic vision, a motion-related ability. We conducted five experiments under blue or orange light to test three important components of dynamic vision: eye pursuit accuracy (EPA, Experiment 1), kinetic visual acuity (KVA, Experiment 1 and 2), and dynamic visual acuity (DVA, Experiment 3-5). EPA was measured by the distance between fixation and target position when participants tracked a target dot. In the KVA task, participants reported three central target numbers (randomly chosen from 0-9) moving toward participants in the depth plane, with speed sensitivity calculated by a staircase procedure. In the DVA task, the three numbers were presented along the meridian line on the same depth plane, with motion direction (Experiment 3) and difficulty level (Experiment 4) manipulated, and a blue light filter lens was used to test the ipRGCs contribution (Experiment 5). Results showed that blue light enhanced EPA and DVA, but reduced KVA. Further, DVA enhancement was modulated by difficulty level: blue light enhancement effect was found only with hard task in the downward motion in Experiment 3 and with the low contrast target in Experiment 4. However, this blue light enhancement effect was not caused by mechanism of ipRGCs, at least not in the range we tested. In this first study demonstrating the relationship between different components of dynamic vision and blue light, our findings that DVA can be enhanced under blue light with hard but not easy task indicate that blue light can increase the sensitivity of dynamic visual discrimination when needed.