Selection 2: Protecting Vision and Hearing
(biology)

Many young adults who spend too much time in the sun without protecting their eyes end up with poor vision later in life. Many young adults damage their hearing so gradually that they are not aware of it until it is too late. In the selection below, you will learn about common causes of vision and hearing loss and ways you can minimize your risks of both types of damage. In the following selection, you will encounter some special terms that refer to parts and disorders of the eye and ear. They may be new to you, but they should not keep you from understanding the points the author is making about steps you can take to prevent vision and hearing loss.

Age can be accompanied by a serious loss of vision and hearing. The time to start preventive measures for such problems, however, is when we are younger.

Preventing a Loss of Vision

1. The eye is subject to both injuries and disorders. Although flying objects sometimes penetrate the cornea and damage the iris, lens, or retina, careless use of contact lenses is the most common cause of injuries to the eye. Injuries cause only 4% of all cases of blindness; the most frequent causes are retinal disorders, glaucoma, and cataracts, in that order. Retinal disorders are varied. In diabetic retinopathy, which blinds many people between the ages of 20 and 74, capillaries to the retina burst, and blood spills into the vitreous humor Careful regulation of blood glucose levels in these patients may be protective. In macular degeneration, the cones are destroyed because thickened choroid vessels no longer function as they should. Glaucoma occurs when the drainage system of the eyes fails, so that fluid builds up and destroys nerve fibers responsible for peripheral vision. Eye doctors always check for glaucoma, but it is advisable to be aware of the disorder in case it comes on quickly. Those wo have experienced acute glaucoma report that the eyeball feels as heavy as a stone. In cataracts, cloudy spots on the lens of the eye eventually pervade the whole lens. The milky yellow-white lens scatters incoming light and blocks vision.
2. There are preventive measures that we can take to reduce the chance of defective vision as we age. Accumulating evidence suggests that both macular degeneration and cataracts, which tend to occur in the elderly, are caused by long-term exposure to the ultraviolet rays of the sun. It is recommended, therefore, that everyone, especially those who live in sunny climates or work outdoors, wear glass, not plastic, sunglasses to absorb ultraviolet light. Large lenses worn close to the eyes offer further protection. Special purpose lenses that block at least 99% of UV-B and 60% of UV-A, and 20-97% of visible light are good for bright sun combined with sand, snow, or water. Healthcare providers have found an increased incidence of cataracts in heavy cigarette smokers. In men, smoking 20 cigarettes or more a day, and in women, smoking more than 35 cigarettes a day doubles the risk of cataracts. It is possible that smoking reduces the delivery of blood and therefore nutrients to the lens.

Preventing a Loss of Hearing

3. Especially when we are young, the middle ear is subject to infections that can lead to hearing impairment if they are not treated promptly by a physician. The mobility of ossicles (the stirrup, hammer, and anvil, which are the three small bones in the middle ear) decreases with age, and in the condition called otosclerosis, new filamentous bone grows over the stirrup, impeding its movement. Surgical treatment is the only remedy for this type of conduction deafness. However, age associated nerve deafness due to stereocilia damage from exposure to loud noises is preventable. Hospitals are now aware that even the ears of the newborn need to be protected from noise and are taking steps to make sure neonatal intensive care units and nurseries are as quiet as possible.
4. In today's society, exposure to excessive noise is often possible. Noise is measured in decibels, and any noise above a level of 80 decibels could result in damage to the hair cells of the spiral organ (organ of Corti). Eventually, the stereocilia and then the hair cells disappear completely. If listening to city traffic for extended periods can damage hearing, it stands to reason that frequent attendance at rock concerts, constantly playing a stereo loudly and using earphones at high volume are also damaging to hearing. The first hint of danger could be temporary hearing loss, a "full" feeling in the ears, muffled hearing, or tinnitus (e.g., ringing in the ears). If you have any of these symptoms, modify your listening habits immediately to prevent further damage. If exposure to noise is unavoidable, specially designed noise reduction earmuffs are available, and it is also possible to purchase earplugs made from a compressible, spongelike material at the drugstore or sporting-goods store. These earplugs are not the same as those worn for swimming, and they should not be used interchangeably.
5. Aside from loud music, noisy indoor and outdoor equipment, such as a rugcleaning machine or a chain saw, are also troublesome. Even motorcycles and recreational vehicles such as snowmobiles and motocross bikes can contribute to a gradual loss of hearing. Exposure to intense sounds of short duration, such as a burst of gunfire, can result in an immediate hearing loss. Hunters may have a significant hearing reduction in the ear opposite the shoulder on which the gun is carried. The butt of the rifle offers some protection to the ear nearest the gun when it is shot.
6. Finally, people need to be aware that some medicines are ototoxic (damaging to hearing and balance). Anticancer drugs, most notably cisplatin, and certain antibiotics (e.g., streptomycin, kanamycin, gentamicin) make the ears especially susceptible to hearing loss. Anyone taking such medications needs to be especially careful to protect his or her ears from any loud noises.

Source: Sylvia Mader, Biology, 8th ed., New York: The McGraw-Hill Companies, Inc., 2004, p. 727.

Writing Prompts

Directions: Type your responses to the items below.

1			In the section "Preventing a Loss of Hearing," list the four major causes of hearing loss that the author identifies. —otosclerosis from middle ear infections —exposure to excessive noise, especially prolonged exposure —exposure to intense sounds of short duration —ototoxic medicines.
2			What changes could you make in your lifestyle that would help prevent vision and hearing loss (or additional) later in your life?
3			Explain why someone who works for a lawn care or tree care company might be more likely to suffer a hearing loss than someone who works as a computer programmer.
4			Do you think a vision or hearing loss would be the more difficult condition for a person to deal with? Explain your reasoning.

To the Web

Consult one or more of the following websites that pertain to the topic of the reading selection. Then answer the questions based on information obtained from the websites.

This is the "Safety" section of the website for Prevent Blindness America.

5			What percent of eye accidents are preventable? In what setting –work, school, home, sports venues—do most eye injuries occur? Why do you think this is so? At the website, click on one of the following categories that interests you most: Home Safety, Sports Safety, Safety at Work, Car Battery Safety, UV Safety, or Fireworks Safety. (If there is a "Safety List" button for the one you choose, click on it to see the list of safety suggestions. Some of the categories also have quick, interesting quizzes you can take.)
6			Tell which category you chose, and then list at least four important safety suggestions you found there.

http://www.hear-it.org/forside.dsp?forside=yes&area=34

This selection gives statistics about the number of hearing impaired people.

7			Approximately how many people worldwide suffer from hearing loss and would benefit from using a hearing aid?
8			With regard to hearing impairment, what problems in particular are faced by people living in developing countries (poorer countries that do not have strong, industrialized economies)?

http://www.hear-it.org/page.dsp?forside=yes&area=260

This selection at the Hear-It website is entitled, "Take Care of Your Ears." It offers suggestions for preventing hearing loss.

9			Are there any of the four guidelines concerning noise that you are not currently following? If so, which ones? Explain why you would or would not follow all of the noise guidelines. If you already follow the guidelines, tell how you became aware of them, how long you have followed them, and the reason you follow them.

http://www.hear-it.org/page.dsp?page=2821

This selection is entitled, "Exercise Is Good for Your Hearing."

10			What is the reason exercise seems to be good for your hearing?
11			For people who work in noisy jobs, how important is it for them to exercise? Explain your answer.