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The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance. Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device.
Eyes can be the most visible parts of organisms, and this can act as a pressure on organisms to have more transparent eyes at the cost of function. [40] Eyes may be mounted on stalks to provide better all-round vision, by lifting them above an organism's carapace; this also allows them to track predators or prey without moving the head. [8]
An eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle helps in the movement of eyelid. The human eyelid features a row of eyelashes along the eyelid margin, which helps in protection of the eye from dust and foreign debris. The main function of eyelid is to keep the cornea moist and clean.
Swordfish also possess an impressive visual system. The eye of a swordfish can generate heat to better cope with detecting their prey at depths of 2000 feet. [58] Certain one-celled microorganisms, the warnowiid dinoflagellates have eye-like ocelloids, with analogous structures for the lens and retina of the multi-cellular eye. [59]
Their eyes transmit a message directly to the muscles without the intermediate processing provided by a brain. [21] During the Cambrian explosion, the development of the eye accelerated rapidly, with radical improvements in image-processing and detection of light direction. [30] The nautilus eye functions similarly to a pinhole camera.
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. [3]
The optical component is concerned with producing a reduced inverted image on the retina. The eye's optical system consists of not only two but four surfaces—two on the cornea, two on the lens. Rays are refracted toward the midline. Distant rays, due to their parallel nature, converge to a point on the retina.
The structure of the eye is presented as a hierarchy, starting first with the part that is most directly responsible for sight, and working down towards the parts which exists only to facilitate this function. The lens, described as white, transparent, and luminous have a composition which lends itself to quickly receive colors. As opposed to ...