Impaired vision and blindness are common. About 3.4 million people in the US are blind or visually impaired. Vision is usually measured by visual acuity charts, and normal vision is expressed as 20/20 ...
Normal human color vision at photopic light levels is trichromatic and relies on the stimulation of three types of cone photoreceptors. While intrinsically photosensitive retinal ganglion cells ...
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