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Chapter-13 Eyes

BOOK TITLE: Optician’s Guide (A Mannual for Opticians)

Author
1. Bhootra Ajay Kumar
ISBN
9789351528241
DOI
10.5005/jp/books/14237_14
Edition
3/e
Publishing Year
2018
Pages
6
Author Affiliations
1. Kolkata, India, Kolkata, West Bengal, India, Diploma in Sportvision (UK), Krishnalaya School of Optometry, Kolkata, West Bengal, India, ICLEP FIACLE (Australia); (UK)
Chapter keywords
Eyeball, outer coat, middle coat, inner nervous coat, refractive media, aqueous humor, vision, myopia, hypermetropia, astigmatism, presbyopia, accommodation

Abstract

Eye is the organ of vision which contains two types of visual receptors, the rod cells and cone cells. Each eyeball is nearly spherical, fluid filled ball and is approximately 2.5 cm in diameter. The eyeball is covered by outer, middle, and inner coats. The outermost tough fibrous layer of the eyeball is called the fibrous coat. It has two parts; cornea and sclera. Middle coat is the vascular coat of the eyes and has choroid and ciliary body. Retina is the innermost light sensitive nervous layer and is present at the posterior side of the eyeball between the choroid and vitreous humor. Cornea, aqueous humor, lens, and vitreous humor are four refractive media of the eye, which help to converge the light rays and focus them on the retina. A detailed description on mechanism of vision, defects of vision, and accommodation has been presented in this chapter.

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