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Running head: SENSORY SYSTEM Sensory System July 16, 2009 Sensory System Part 1 Cataract Cataract is a clouding of the lens in the eye. This clouding affects normal vision. In order to understand how does cataract formation represent a variance from normal anatomy and physiology, it is important to understand the lens and its functioning. The lens is a clear part of human eye helping to focus image or light on the retina (the light-sensitive tissue at the back of the human eye. In a normal eye without cataract, the light is able to pass through the clear and transparent lens directly to the retina. When the light reaches retina, it is transformed into nerve signals that are then sent to the human brain (Cataract).
In a normal eye the lens is clear and transparent, so the retina is able to receive a clear and sharp image. When the patient has a cataract, the lens is cloudy, and the patient cannot see clear images as they are blurred. There are several types of cataract. Most of them are related to aging; however, there are other types, such as traumatic, secondary, congenital and radiation cataract. There are three basic types of cataract: a subcapsular cataract (begins at the back of the lens and is often observed in patients with diabetes, retinitis pigmentosa or high farsightedness), a nuclear cataract (most common form that forms due to natural aging changes, begins in the nucleus, the center of lens), and a cortical cataract (forms in the lens cortex and extends from the outside of the lens to the center) (Learn About Cataract). A patient with cataract reports blurry or cloudy vision.
The colors usually seem faded, and lamps, headlights or sunlight seem to be too bright or blaring. Sometimes a halo appears around lights or colors may seem not as bright as they once did. The patient usually reports multiple images in one eye, and poor night vision. When the nuclear cataract develops, the patient may notice a temporary improvement in his near vision; however, this improvement never lasts long and disappears as the cataract progresses. What happens in sensorineural hearing loss? Sensorineural hearing loss (also known as sensorineural deafness or deafness) accounts for 90 % of all hearing loss.
Sensorineural hearing loss happens when there is a damage to the nerve pathways from the inner ear (retro cochlear) to the brain or to the inner ear (cochlea) (Different Types Of Hearing Loss). This is a permanent hearing loss and cannot be surgically or medically corrected. In this type of hearing loss, the damage is in the acoustic nerve, in the inner ear or both. There are over 30, 000 hearing nerve endings in the cochlea (Sensorineural Hearing Loss). The nerve endings (hair cells) in the large end react to high-pitched sounds, and the nerve endings in the small end respond to low-pitched sounds.
These endings are very susceptible to damage due to various reasons. Sensorineural hearing loss can be caused by birth injury, genetic syndromes, various diseases; as a result of viruses, noise exposure, aging, head trauma, tumors, etc. The patient suffering from a sensorineural hearing loss loses ability to hear faint sounds, and reports reduction in sound level. The ability to hear clearly and speech understanding are also impaired. The patients reports that sounds heard are distorted, quieter and less clear; high tones are less audible, sounds f, s, z are not heard (Sensorineural Hearing Loss). Sometimes the patients report difficulties in understanding speech if there is background noise.
Works Cited Cataract. (n. d. ). Retrieved July 16, 2009, from web Different Types Of Hearing Loss. (n. d. ). Retrieved July 16, 2009, from web Learn About Cataract. (n. d. ).
Retrieved July 16, 2009, from web Sensorineural Hearing Loss. (n. d. ). Retrieved July 16, 2009, from web
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Research essay sample on Running Head Sensory System
