Encyclopedia of Health and Medicine

72 The Eyes
EYE CHANGES OF AGING AND THEIR EFFECTS ON VISION
Physical Change Resulting Health Condition Effect on Eyes or Vision
death of cones in the macula AGE-RELATED MACULAR DEGENERATION (ARMD) diminished VISUAL ACUITY in the center of
vision
white rim around the CORNEA arcus senilis none
LENS cloudiness and discoloration CATARACT blurred or hazy vision; faded colors;
progressive loss of vision
“STROKE” of the OPTIC NERVE that ISCHEMIC OPTIC NEUROPATHY diminished visual acuity; decreased
interrupts the flow of blood
VISUAL FIELD; progressive loss of vision
slowed chemical reactions in NIGHT BLINDNESS diminished visual acuity in low-light
the rods
circumstances
liquefaction of the vitreous humor VITREOUS DETACHMENT FLOATERS
loss of lens FLEXIBILITY PRESBYOPIA diminished ability to focus on near objects
atrophy (weakening) of the eyelid PTOSIS; ECTROPION partial occlusion of visual field; can cause
muscles and tissues, shifting of
CONJUNCTIVITIS, KERATITIS, CORNEAL INJURY
the orbital fat pads
fiers for reading and close work, adjustments on
televisions and computers to enlarge screen
images, voice-activated telephone dialers, highintensity
light sources, and screen readers with
voice output are among the devices available to
accommodate low vision.
See also GENERATIONAL HEALTH-CARE PERSPECTIVES;
VISION HEALTH.
amblyopia A VISION IMPAIRMENT, commonly called
“lazy eye,” in which the pathways between the
EYE and the BRAIN do not properly handle the
processes of sight. Amblyopia is most common in
children. The impairment often develops when
there are circumstances that allow one eye to
become dominant in sending NERVE impulses to
the brain, such as STRABISMUS (the inability of the
eyes to focus on the same object) or congenital
cataracts (opacity of the lens). Amblyopia can also
develop when there is significant disparity in the
refractive capabilities of the eyes, such as when
one eye is hyperopic (farsighted) or myopic (nearsighted)
and the other eye has normal vision. The
brain becomes accustomed to messages the dominant
eye and “ignores” nerve signals from the
nondominant, or “lazy,” eye. Untreated amblyopia
can result in permanent vision impairment or
legal blindness.
The diagnostic path includes close examination
of the eyes to determine whether other disease
processes are present that might account for the
vision deficit. Treatment targets those processes,
such as cataracts or REFRACTIVE ERRORS, when they
exist. When the eye is otherwise healthy and normal,
treatment consists of forcing the brain to rely
on the amblyopic eye, usually by patching the
dominant eye for structured periods of time.
Sometimes the ophthalmologist will substitute
atropine drops in the eye, which dilate the pupil
and distort the eye’s ability to focus, when a child
refuses to wear an eye patch or an eye patch is
otherwise not the most appropriate therapeutic
choice. The dilation interferes with the eye’s ability
to focus, forcing the brain to interpret nerve
messages from the untreated eye.
When detected and treated in children who are
under age 9, most amblyopia responds to treatment
and vision returns. Delayed or inadequate