Eye diseases. The structure of the lens and vitreous body (the most important)

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Eye diseases. The structure of the lens and vitreous body (the most important)

Lecture notes, cheat sheets

Directory / Lecture notes, cheat sheets

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6. The structure of the lens and vitreous body

The transparent contents of the eyeball are represented by aqueous humor, the lens and the vitreous body.

Aqueous moisture is enclosed in the anterior and posterior chambers of the eye. Its quantity in children does not exceed 0,2 cm³, and in adults it reaches 0,45 cm³.

The anterior chamber is the space bounded by the posterior surface of the cornea in front, the iris behind, and in the region of the pupil by the lens. The chamber has the greatest depth in the center, to the periphery it gradually decreases. In a newborn, mainly due to the greater sphericity of the lens, the anterior chamber is smaller than 1,5 mm.

The place where the cornea passes into the sclera, and the iris into the ciliary body, is called the angle of the anterior chamber of the eye. Through the angle of the anterior chamber, aqueous and anterior ciliary veins, aqueous humor is drained.

The posterior chamber is the space bounded anteriorly by the iris and posteriorly by the anterior surface of the lens. Through the region of the pupil, the posterior chamber communicates with the anterior one.

The lens is a transparent elastic body, has the shape of a biconvex lens. In newborns, the lens is almost spherical in shape. With age, the lens flattens somewhat, the radius of curvature of the anterior surface increases from 6 to 10 mm, and the posterior surface from 4,5 to 6 mm. The anteroposterior size of the lens of a newborn is 4 mm, and the diameter is 6 mm; the lens of an adult is 44,5 and 10 mm, respectively.

The lens has anterior and posterior surfaces, anterior and posterior poles, a sagittal axis and an equator. The lens is held in place by the ciliary body using the ligament of cinnamon. The lens contains a capsule and lenticular, or cortical, fibers. In children, the fibers are elastic; with age, the center of the lens becomes denser, and from the age of twenty-five thirty, a core begins to form, which gradually increases in size. The lens is made up of 65% water. It performs a refractive function; in relation to the average refractive power of the eye, it accounts for up to 40 out of 7780 diopters in newborns, and by the age of fifteen, 20 out of 60 diopters.

The vitreous body is the main supporting tissue of the eyeball. Its weight in a newborn is 1,5 g, in an adult 67 g. The vitreous body is a formation of a gelatinous consistency, 98% consisting of water, containing an insignificant amount of protein and salts. In addition, it has a thin connective tissue skeleton, thanks to which it does not blur, even if taken out of the eye. On the anterior surface of the vitreous body there is a recess, the so-called plate-shaped fossa, in which lies the posterior surface of the lens.

The vitreous body, being a transparent medium, provides free passage of light rays to the retina, protects the inner membranes (retina, lens, ciliary body) from dislocation. This allows you to perform the accommodative function of the eye, one of the main functions of the organ of vision.

Author: Shilnikov L.V.

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