The layers of the eye and the lens serve as boundaries for three chambers within the eye
The chambers of the eye are
• Anterior chamber, the space between the cornea and the iris
• Posterior chamber, the space between the posterior surface of the iris and the anterior surface of the lens
• Vitreous chamber, the space between the posterior surface of the lens and the neural retina (Fig. 23.2). The cornea, the anterior and posterior chambers, and their contents constitute the anterior segment of the eye; the vitreous chamber, visual retina, RPE, posterior sclera, and uvea constitute the posterior segment.
The retractile media components of the eye alter the light path to focus it on the retina
As light rays pass through the components of the eye, they are refracted. Refraction focuses the light rays on the photoreceptors of the retina. Four transparent components of the eye, called the refractile (or dioptric) media, alter the path of the light rays:
• Cornea, the anterior window of the eye
• Aqueous humor, the watery fluid located in the anterior and posterior chambers
• Lens, a transparent, crystalline, biconcave structure suspended from the inner surface of the ciliary body by a ring of radially oriented fibers, the zonule of Zinn
• Vitreous body, composed of a transparent gel substance that fills the vitreous chamber. It contains hyaluronic acid, widely dispersed collagen fibrils, and other proteins and glycoproteins. The fluid component of the vitreous body is called the vitrous humor.
The cornea is the chief refractive element of the eye. It has a refractive index of 1.376 (air has a refractive index of 1.0). The lens is second in importance to the cornea in the refraction of light rays. Because of its elasticity, the shape of the lens can undergo slight changes in response to the tension of the ciliary muscle. These changes are important in accommodation for proper focusing on near ob-
superior rectus muscle ora serrata ciliary body conjunctiva canal of Schlemm anterior chamber pupil cornea
ora serrata inferior rectus muscle retinal pigment epithelium superior rectus muscle
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