Nursing 109

N109: Foundations in Nursing Practice Study Guide • Presbyopia: This is a condition in which the lens of the eye loses its ability to focus, making it difficult to see objects up close. The lens of the eye needs to change its length or shape to focus on smaller objects, or objects that get closer or farther away. This is called the elasticity of the lens. This elasticity is slowly lost as people age. The result is a slow decrease in the ability of the eye to focus on nearby objects. People usually notice the condition at around age 45, when they realize that they need to hold reading materials further away in order to focus on them. Presbyopia is a natural part of the aging process and it affects everyone. This condition can be corrected with glasses or contact lenses. • Myopia : This is also called nearsightedness, and is a condition in which the focusing power (refraction) of the eye is greater than that required for clear vision of distant objects. Myopia is a common cause of visual disability throughout the world. This condition can be corrected with glasses, contact lenses, or surgical intervention. • Hyperopia : This is also called farsightedness, and is greater difficulty seeing near objects than distant objects. Farsightedness is the result of the visual image being focused behind the retina rather than directly on it. It may be caused by the eyeball being too small or the focusing power being too weak. This condition can be corrected with glasses, contact lenses, or surgical intervention. • Photophobia: This is eye discomfort in bright light and is usually a symptom of another eye disorder. Photophobia can be caused by corneal abrasions, some medications, excessive wearing of contact lenses, headaches, eye diseases, and any condition that causes pupil dilation. The treatment is avoiding bright light until theunderlying condition is corrected. • Astigmatism: This is an irregular curvature or uneven contour of the cornea, resulting in impaired light refraction. This causes blurred vision at all distances. Other symptoms include headaches, dizziness, and close work or difficulty reading. Astigmatism can be corrected with glasses or contact lenses. 5.4 Structure and Function of the Ear The ear is a complex organ with multiple functions. First, it receives sound and transmits sound to create the sense of hearing. Second, the ear functions as an aid in balance and body position (proprioception). Sound is a form of energy that moves through air, water, and other matter in waves of pressure. The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz (the audio range). Although the sensation of hearing requires an intact and functioning auditory portion of the central nervous system, as well as a working ear, human deafness (extreme insensitivity to sound) most commonly occurs because of abnormalities of the inner ear, rather than the nerves or tracts of the central auditory system. The ear is commonly divided into three major parts: outer, middle, and inner ear.

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