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Eye color. The irises of human eyes exhibit a wide spectrum of colours. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye 's iris [1] [2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. [3] : 9. In humans, the pigmentation of the iris varies ...
3–6 million per year (US) [1] [3] Conjunctivitis, also known as pink eye, [4] is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. [5] It makes the eye appear pink or reddish. [1] Pain, burning, scratchiness, or itchiness may occur. [1] The affected eye may have increased tears or be "stuck ...
Infectious bovine keratoconjunctivitis ( IBK ), also known as pinkeye, New Forest eye or blight, [1] is a veterinary infection of cattle caused by Moraxella bovis, a Gram-negative, β-haemolytic, aerobic, rod-shaped bacterium. It is spread by direct contact or by flies serving as vectors. It is the most common ocular disease of cattle (mostly ...
Whatever the cause may be, pinkeye -- or what's referred to medically as conjunctivitis -- is uncomfortable. "Conjunctivitis basically means inflammation of the conjunctiva, which is the clear ...
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] However, he went on that despite the difficulty in ...
Trachoma is an infectious disease caused by bacterium Chlamydia trachomatis. [ 2] The infection causes a roughening of the inner surface of the eyelids. [ 2] This roughening can lead to pain in the eyes, breakdown of the outer surface or cornea of the eyes, and eventual blindness. [ 2] Untreated, repeated trachoma infections can result in a ...
The evolution of color vision in primates is highly unusual compared to most eutherian mammals. A remote vertebrate ancestor of primates possessed tetrachromacy, [1] but nocturnal, warm-blooded, mammalian ancestors lost two of four cones in the retina at the time of dinosaurs. Most teleost fish, reptiles and birds are therefore tetrachromatic ...
Color vision. Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity. Color perception is a part of the larger visual system and is mediated by a complex process between neurons that begins with differential stimulation of different ...