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Anatomy of the Eye Anatomy of the Eye Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I, All rights reserved Eyes and Vision Eyesight provides the brain with more input than all other senses combined. Each optic nerve contains one million nerve fibers. It is estimated that more than half of the information in the conscious mind enters through the eyes. The eyes are the most complex of the four special sense organs. All rights reserved All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 1 Anatomy of the Eye Sequence of Vision Rays of light enter the eye through the clear, domed front of the eyeball, the cornea, where they are partly bent (refracted). The rays then pass through the transparent lens, which changes shape to fine-focus the image, a mechanism known as accommodation. The light continues through the fluid, or vitreous humor, within the eyeball and shines an upside-down image onto the retina lining. The retina contains over 120 million cone cells and about 7 million rod signals. All rights reserved Sequence of Vision Rods are scattered through the retina and respond to low levels of light, but do not differentiate colors. Cones are concentrated in the fovea, need brighter conditions to function, and distinguish colors and fine details. Nerve fibers from the rods and cones connect via intermediate retinal cells to the fibers that form the optic nerve. Through this, the image is transmitted to the visual cortex in the brain, where it is turned upright. All rights reserved Path of Light Childhealth-explanation.com Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 2 Anatomy of the Eye Anatomy of the Eye The Human Eye is divided into three layers: Fibrous tunic (scleretic coat) This is the external layer of the eye. Two parts: Sclera (white of the eye) and Anterior Cornea Sclera includes: Episcleral layers Schlemm’s canal Trabecular meshwork Cornea contains: The limbus The following layers: Epithelial - Bowman’s – Stroma – Descemet’s – Endothelium All rights reserved Anatomy of the Eye Vascular tunic (uvea or choroid coat) This is the middle layer that is pigmented with melanin and provides the eye with it’s blood supply. Choroid Capillary lamina of choroids Bruch’s membrane Sattler’s layer Ciliary body Ciliary processes Ciliary muscle Iris Stroma Pupil Iris dilator muscle Iris sphincter muscle All rights reserved Anatomy of the Eye Retina: This is the inner layer of the eye composed primarily of nervous tissue. Its primary function is image formation. It contains: Cells Photoreceptor cells – rods, cones, horizontal Bipolar cells Retinal ganglion cells Layers Rods and cones Retinal pigment epithelium Macula Foveola Fovea All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 3 Anatomy of the Eye Other Parts of the Eye Anterior segment: Anterior chamber Aqueous humor Posterior chamber Lens Posterior segment Vitreous body (humor) Other Globe Eyelids Lacrimal system Orbit Optic nerve and visual pathways All rights reserved Anatomy and Function Conjunctiva: Clear, moist mucous membrane Assists in lubricating the eye Produces mucus and tears along with the lacrimal system Helps prevent foreign objects from penetrating into deeper structures of the eye. All rights reserved Anatomy and Function Sclera: White part of the eye. Opaque, protective, outer layer. Maintains the shape of the globe. Offers resistance to internal and external forces. Continuous with the dura mater and the cornea. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 4 Anatomy of the Eye Anatomy and Function Cornea: Transparent fibrous coat the covers the front of the eye, including the iris, pupil and anterior chamber. Works with lens to refract light. After light enters the interior the light rays are bent so they can be brought to a fixed focus. Accounts for around two-thirds of the eye’s optical power. All rights reserved Choroid – Vascular Tunic Getty Images All rights reserved Choroid Is a highly vascular structure composed of capillaries and small arteries and veins that include connective tissue. It lies between the sclera and retina. It provides oxygen and other nutrients to the outer layers of the retina and together with the ciliary body and the iris, it forms the uveal tract. The choroid contains melanin which helps limit uncontrolled reflection within the eye that could result in the perception of mixed-up images. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 5 Anatomy of the Eye Ciliary Body Controls accommodation (the process by which the eye changes optical power to maintain a clear image as the distance changes). Regulates flow of the aqueous humor into Schlemm’s canal. Coated by the epithelium, which produces the aqueous humor. All rights reserved Iris Is the colored part of the eye. Responsible for controlling the size and diameter of the pupil and the amount of light reaching the retina. Divides the area between the lens and the cornea into an anterior and posterior chamber. This is the primary location where intraocular pressure is regulated. Failure to control intraocular pressure can lead to disease, such a glaucoma. All rights reserved Retina The retina is a light-sensitive tissue lining that covers approximately 65% of the back inner surface of the eye. Rod and cone photosensitive cells, convert light energy into signals that are carried to the brain by the optic nerve. The fovea or fovea centralis (a small dimple) is the center of the eye’s sharpest vision and has the most color perception. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 6 Anatomy of the Eye Rods and Cones All rights reserved Rods and Cones There are two distinct visual systems in the eye: Photopic vision is more sensitive to light, not color sensitive and is made up of rod cells. Scotopic vision is less sensitive to light, color sensitive and is made up of cone cells. The cylindrical shaped rod cells are located on the outer edges of the retina. Mainly used in peripheral vision, and because they require less light to function are also responsible for night vision. All rights reserved Rods and Cones There are three different types of cone cells, each of which absorb light from a different portions of the light spectrum. Cones that absorb long-wavelength light (reds) Cones that absorb middle-wavelength light (greens) Cones that absorb short-wavelength light (blues) Cone cells are a specialized type of nerve cell that are responsible for color perception and visual acuity. The macula located in the central area of the retina contains the cone cells. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 7 Anatomy of the Eye Other Parts of the Eye Anterior Chamber: Is a space in the eye filled with aqueous humor, and lies between the iris and the cornea’s endothelium. Aqueous Humor: Flows through the pupil into the anterior chamber through a narrow cleft between the front of the lens and the back of the iris. Its main function is to provide optical power to the cornea. Also maintains intraocular pressure, shapes the globe. All rights reserved Other Parts of the Eye Posterior Chamber: Is the space behind the iris and in front of the lens. Holds aqueous humor for later transport to the anterior chamber. Lens: Is just in front of the iris. When the lens is relaxed, it’s flattened (increase in diameter – more light comes in) When the lens is contracted (decrease in diameter – less light comes in) This is called curvature of the lens and it enables the eye to adjust its focus between near and far objects. All rights reserved Other Parts of the Eye Lacrimal system: Contains structures for tear production and drainage. Lacrimal gland secretes tears and with its ecretory ducts, moves the fluid to the surface of the eye providing both normal amounts on the surface of the eye and extra amounts for tears. Vitreous body: Is the transparent, colorless, gel that fills the space between the lens and the retina. It holds the eye taut. This gel does not get replenished. Keeps the retina in place by pressing against the choroids and adhering to the retina. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 8 Anatomy of the Eye Optic Nerve The optic nerve is also known as the cranial nerve (CN) II. It transmits visual information from the retina to the brain. Is considered part of the CNS Three layers: Dura Arachnoid Pia mater All rights reserved Diseases and Disorders Retinal detachment: Retina is pulled or lifted away from its normal position. Cataracts: A partial or complete clouding on or in the lens which may obscure vision Myopia – nearsightedness Hypermetropia – farsightedness Glaucoma: A group of diseases characterized by damage to the optic nerve All rights reserved Diseases and Disorders Conjunctivitis: An infection of the conjunctiva Blepharitis: An inflammation of the eyelash follicles along the edge of the eyelid Corneal ulcers: An open sore on the cornea Dacryoadenitis: An inflammation of the tear-producing lacrimal gland. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October
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