HEALTH AND AGING TEXTBOOK NOTES
¾ The structures of the inner ear that sense gravity and head position can also degrade overtime, leading
to dizziness and falls.
¾ Presbycusis, or hearing loss with age, is the most common hearing problem.
¾ On average, men lose 80% of hearing capacity by age 90, but women only lose about 30%.
¾ Severe loss can result from exposure to loud noises such as factory machinery, jet planes, military
equipment and even music.
¾ The damage can be temporary, as in the loss of hearing for a day or two after a rock concert, but over
time such damage can become permanent.
¾ Risk factors included ototoxic drug use and occupations with high noise exposure, whereas exercise
was protective, probably due to its positive effects on blood flow.
¾ One may lose a sense of connection to the environment.
¾ A decreased willingness to communicate with others, or to mingle in social settings, frequently
accompanies diminished hearing. Use of hearing aids can migrate hear loss, but people often complain
that aids do not allow then to focus or screen out unwanted sounds.
¾ Tinnitus, often defined as ringing in the ears with no discernable cause, is another common problem
with age. It has many sources, including ear infections, high blood pressure, diabetes, tumors,
atherosclerosis, malnutrition, medications, and toxic chemicals.
¾ If tinnitus becomes severe, however, it can be very distracting and interfere with sleep and everyday
¾ Light passes through the cornea, a transparent structure that protects the eye. By contracting and
dilating, muscles in the iris regulate the amount of light that enters the eye.
¾ At the back of the eye is the retina, which contains photoreceptors (rods and cones).
¾ The lens focuses the image on the retina, adjusting for the distance of the object. The photoreceptors
then translate light energy into action potentials in the optic nerve.
¾ Cones are responsible for the colour vision, whereas rods only transmit information in black and white,
although they are more sensitive to light. Cones are most numerous in the macula.
¾ Rods are typically found in the more peripheral regions of the retina.
¾ The whole structure is supported by gel-like substances called humors in the chamber in the eye.
¾ Aqueous (watery) humor not only provides support but also transport nutrients and wastes, whereas the
more gel-like vitreous humor protects the eye against shock.
¾ The conjunctiva, a clear mucus membrane inside the eyelids, also provides protection.
¾ The cornea, lens, and vitreous humor all diminish in transparency, reducing the amount of light
entering the eye also scattering the light that does come in, making the eye more sensitive to glare.
¾ Yellowing of the lens also decreases its transparency and makes it difficult to differentiate blues,
greens, and violets.
¾ The lens loses elasticity with age, making it more difficult to focus on near objects. This is called
presbyopia and is the most common age-related visual problem.
¾ The muscles in the iris decrease in number and strength with age, and its collagen stiffens, reducing the
ability of the pupil to enlarge.
¾ These changes in the iris also decrease the speed at which it responds to light, so it stays open
fractionally too long when the eye is exposed to bright light and does not expand quickly enough when
the light dims. This makes older adults more vulnerable to glare and reduces their ability to see at
¾ The fluids in the eye also show age-related changes.
¾ The rate at which aqueous humor is generated also declines, and there might not be enough to properly
maintain the shape of the cornea. Vitreous humor also decreases in size and becomes more liquid.
¾ The retina also undergoes age-related changes. Cones and rods loss sensitivity progressively from
adolescents through the remainder of the lifespan.
¾ Cones are stable, but rods in the central retina are vulnerable to aging.
light. Optic nerve fibers are also lost, decreasing the quality of vision.
¾ The four most common serious diseases of the eye in late life are cataracts, macular degeneration,
glaucoma, and diabetic retinopathy.