Caring for your vision and hearing

1. Chapter 2 Caring for your vision and hearing Lesson 4

2. My eye • Eye is the organ of vision

3. My eye • The process of vision occurs as follows: • Iris: the colored part that opens and closes to adjust the amount of light that can enter the eye. • Light enters the eye through cornea, pupil and lens. • Lens focuses light to form an image on the retina. • Retina is located at the back of the eye, and produces signals through the nerve cells in the optic nerve when it receives an image. • The brain receives the signals from the optic nerve and interprets them to produce a mental image.

4. Eye problems

5. Eye problems • Nearsightedness is a vision problem in which the retina is too far behind the lens, so, people with this problem can’t see distant objects well. • Farsightedness is a vision problem in which the retina is too close to the lens, so, people with this problem can’t see nearby objects well. • In both cases above, people will see the objects as a blurry “unclear” image. • Astigmatism is a vision problem in which the lens or cornea has a wrong shape. This causes blurred, uneven vision.

6. Eye problems nearsightedness farsightedness astigmatism

7. Eye problems • All of the eye problems can be corrected with eyeglasses or contact lenses.

8. Eye problems • Conginctivitisis an infection of the tissue on the outside of the eye and tissues under the eyelid. • Its symptoms include painful, red eyes and a thick discharge from the eyes. • Treatment is by applying clean, warm compresses “treatment pads”, and doctor may suggest eye drops.

9. Eye problems • Sty is an infection of the oil or sweat glands in the eyelid. • It is caused by the blockage of a hair follicle. • Treatment is by applying clean, warm compresses “treatment pads”, and not squeezing sites.

10. What can affect the eye? • Flying objects • Impact with an object • Ultraviolet rays: • Years of exposure to UV rays can cause cataracts; which is clouding of the lenses, and this can lead to blindness.

11. How can you protect your eyes? Avoid touching your eyes unless your hands have just been washed. Never look directly into the sun. Never share washcloths or towels with others. Keep sharp objects away from your eye. Wear safety glasses when working with dangerous objects.

12. Eye physicians • Optometrist is an eye doctor who tests eyes for focusing ability, side vision, and colors distinguishing, and then prescribes eye wear. • Ophthalmologist is an eye doctor for medical eye problems.

13. My ear • Ear is the organ of hearing.

14. My ear • The process of hearing occurs as follows: • Outer ear collects sound waves, and sends them to the eardrum. • The eardrum vibrates, and accordingly, three tiny bones in the middle ear “hammer, anvil, and stirrup” amplify vibrations. • 3. The vibrations stimulate tiny hair-like cells lining the cochlea in the inner ear, to vibrate and send signals to the brain through auditory nerve.

15. My ear •  The semicircular canals in the inner ear help keep body’s balance. • The brain senses the movement of the fluid in these canals as the body move.

16. How can you protect your ears? The ear canal is lined with hair follicles and wax-producing glands, which help keep foreign matter out of the ear. Don’t put anything -even a cotton swab- into your ear canal This is because you could puncture your delicate eardrum, so, it can become infected.

17. Effects of sounds

18. How can you protect your ears? The loudness of the sounds is measured in units called decibels. Sounds at or above 80 decibels can damage the hair cells in the cochlea causing permanent hearing loss. Wear earplugs or ear protectors if you must be near loud noise.

19. How can you protect your ears? If you listen to music with headphones, keep the volume down. If others can hear the music from your headphones, it is too loud.