尽管产生图像的不是视觉类型，但有些完全盲的人可能无法以视觉方式感知光线。 证据始于1923年由哈佛大学研究生克莱德·基勒（Clyde Keeler）进行的研究项目。 基勒（Keeler）饲养了一种具有突变的小鼠，其眼睛缺少视网膜感光细胞。 尽管小鼠缺乏视力所需的视杆和视锥，但它们的瞳孔对光有反应，并保持昼夜周期设定的昼夜节律。 八十年后，科学家在小鼠和人眼中发现了称为固有光敏性视网膜神经节细胞（ipRGC）的特殊细胞。 ipRGC位于从视网膜向大脑传导信号的神经上，而不是视网膜本身上。 这些细胞在检测光的同时却不影响视力。 因此，如果一个人至少有一只眼睛可以接收光（无论有没有看见），理论上他或她就可以感知明暗。
新加坡物理作业代写: 周期设定
Although the image is not of a visual type, some completely blind people may not be able to visually perceive light. The evidence began in 1923 with a research project conducted by Harvard University graduate student Clyde Keeler. Keeler raised a mouse with mutations that lacked retinal photoreceptors in the eye. Although mice lack the rods and cones required for vision, their pupils respond to light and maintain the circadian rhythm set by the day and night cycle. Eighty years later, scientists discovered special cells called intrinsic photosensitive retinal ganglion cells (ipRGC) in mice and human eyes. ipRGC is located on the nerve that signals from the retina to the brain, not the retina itself. These cells detect light without affecting vision. Therefore, if a person has at least one eye that can receive light (with or without seeing it), he or she can theoretically perceive the light and shade.