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In visual physiology, adaptation is the ability of the retina of the eye to adjust to various levels of light. Natural night vision, or scotopic vision, is the ability to see under low-light conditions. In humans, rod cells are exclusively responsible for night vision as cone cells are only able to function at higher illumination levels. [1]
The human eye is a sensory organ in the visual system that reacts to visible light ... full adaptation through adjustments in retinal rod photoreceptors is 80% ...
The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of "design."In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [3]
Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye [7] Most vertebrate photoreceptors are located in the retina. The distribution of rods and cones (and classes thereof) in the retina is called the retinal mosaic. Each human retina has approximately 6 million cones and 120 million rods. [8]
The visual system includes the eyes, the connecting pathways through to the visual cortex and other parts of the brain (human system shown). The eye is the sensory organ of the visual system. The iris , pupil , and sclera are visible
Right human eye cross-sectional view; ... Vision is an important adaptation in higher vertebrates. ... It passes through the other layers, ...
A horse has higher acuity through most of the visual field of its eyes than a human has, but does not match the high acuity of the human eye's central fovea region. [45] Spherical aberration limits the resolution of a 7 mm pupil to about 3 arcminutes per line pair.
The young human eye can change focus from distance (infinity) to as near as 6.5 cm from the eye. [32] [33] This dramatic change in focal power of the eye of approximately 15 dioptres (the reciprocal of focal length in metres) occurs as a consequence of a reduction in zonular tension induced by ciliary muscle contraction.