Sensory Systems: Vision and Hearing | Cardiovascular System | Respiratory System | Gastrointestinal System | Endocrine System | Musculoskeletal System | Hematological and Immune Systems | Renal System
Older adults develop significant age-related changes in the
eye, which have important effects on vision. The weakening of the
ciliary muscle, combined with decreased curvature of the lens, results
in a loss of accommodation; therefore, it becomes difficult for
an individual to focus on near objects, and bifocals may be needed.
It is also difficult for elderly people to adapt to light because
of rigidity of the pupil and increasing size and opacity of the
lens. As the lens changes with age, the increased scattering of
light produces glare, which may be bothersome to elderly people.
The pupil becomes smaller in diameter (more miotic) with age, due to
atrophy of the dilator muscle fibers and increased rigidity of the
blood vessels of the iris. This anatomical alteration in the pupil,
combined with the increased thickness of the lens, contributes to
the impairment of the visual performance of older persons at twilight.
The growth in lens thickness causes a change in the absorption of
light, with a decreased sensitivity at the violet end of the spectrum
and a decreased ability to distinguish between blues and greens.
Elderly people also show a decline in their ability to view objects
at rest (static acuity) and in motion (dynamic acuity). Reportedly,
93.5% of individuals ages 40–44 years have a corrected
visual acuity of 20/20 or better compared with 41.9% of
those ages 70–74 years (Weymouth 1960). With
age, the lens opacifies (i.e., becomes less transparent as a result
of protein aggregations), and a cataract can form. Elderly patients
are also at risk for age-related macular degeneration, which causes
loss of central vision when drusen (yellowish-white deposits) accumulate
in the retina. Age-related macular degeneration is the most common
cause of blindness in elderly people (Haegerstrom-Portnoy and Morgan 2007; Harvey 2003).