InterviewSolution
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InterviewSolution
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What are human eye |
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Answer» Parts of eye\tThe adult human eye ball is nearly a spherical structure.\tThe wall of the eye ball is composed of three layers\texternal layer is composed of a dense connective tissue and is called the\xa0sclera\tanterior portion of this layer is called the\xa0cornea\tmiddle layer is\xa0choroid, which contains many blood vessels and looks bluish in colour.\tThe choroid layer is thin over the posterior two-thirds of the eye ball, but it becomes thick in the anterior part to form the ciliary body.\tThe ciliary body itself continues forward to form a pigmented and opaque structure called the\xa0iris\xa0which is the visible coloured portion of the eye.\tThe eye ball contains a transparent crystalline lens which is held in place by ligaments attached to the ciliary body.\tIn front of the lens, the aperture surrounded by the iris is called the\xa0pupil.\tThe diameter of the pupil is regulated by the muscle fibres of iris.\tThe inner layer is the retina and it contains three layers of cells, from inside to outside ganglion cells,\xa0bipolar cells photoreceptor cells.\tThere are two types of photoreceptor cells rods\tPhotoreceptor cells contain the light-sensitive proteins called the\xa0photopigments.\tThe daylight vision and colour vision are functions of cones and the twilight vision is the function of the rods.\tThe rods contain a purplish-red protein called the\xa0rhodopsin\xa0or visual purple, which contains a derivative of Vitamin A.\tIn the human eye, there are three types of cones which possess their own characteristic photopigments that respond to red, green and blue lights.\tThe optic nerves leave the eye and the retinal blood vessels enter it at a point medial to and slightly above the posterior pole of the eye ball.\tPhotoreceptor cells are not present the medial region and hence it is called the\xa0blind spot.\tAt the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called\xa0macula lutea\xa0with a central pit called the\xa0fovea, is a thinned-out portion of the retina where only the cones are densely packed.\tThe space between the cornea and the lens is called the\xa0aqueous chamber\xa0and contains a thin watery fluid called\xa0aqueous humor.\tThe space between the lens and the retina is called the\xa0vitreous chamber\xa0and is filled with a transparent gel called\xa0vitreous humor. The human eye is an organ that reacts with light and allows light perception, color vision and depth perception |
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