What Causes Visual Impairment?
People rarely lose their eyesight during their teen years. When they
do, it's usually caused by an injury like getting hit in the eye or head with a
baseball or having an automobile or motorcycle accident.
Some babies have congenital blindness, which means they are
visually impaired at birth. Congenital blindness can be caused by a number of
things — it can be inherited, for instance, or caused by an infection (like
German measles) that's transmitted from the mother to the developing fetus
during pregnancy.
Conditions that may cause vision loss after birth include:
Amblyopia (pronounced: am-blee-oh-pee-uh)
is reduced vision in an eye caused by lack of use of that eye in early
childhood. Some conditions cause a child's eyes to send different messages to
the brain (for example, one eye might focus better than the other). The brain
may then turn off or suppress images from the weaker eye and vision from that
eye then stops developing normally. This is also known as a "lazy
eye." Strabismus (misaligned or crossed eyes) is a common cause of
amblyopia, since the brain will start to ignore messages sent by one of the
misaligned eyes.
Cataracts are cloudy areas in
part or all of the lens of the eye. In people without cataracts, the lens is
crystal clear and allows light to pass through and focus on the retina.
Cataracts prevent light from easily passing through the lens, and this causes
loss of vision. Cataracts often form slowly and usually affect people in their
60s and 70s, but sometimes babies are born with congenital cataracts. Symptoms
include double vision, cloudy or blurry vision, difficulty seeing in poorly lit
spaces, and colors that seem faded.
Diabetic retinopathy (pronounced: reh-ton-ah-pa-thee)
occurs when the tiny blood vessels in the retina are damaged due to diabetes.
People with retinopathy may not have any problems seeing at first. But if the
condition gets worse, they can become blind. Teens who have diabetes should be
sure to get regular eye exams because there are no early warning signs for this
condition. To help prevent retinopathy, people with diabetes should also avoid
smoking, keep their blood pressure under control, and keep their blood sugar at
an even level.
Glaucoma is an increase in
pressure inside the eye. The increased pressure impairs vision by damaging the
optic nerve. Glaucoma is mostly seen in older adults, although babies may be
born with the condition and children and teens can sometimes develop it as
well.
Macular degeneration (pronounced: mah-kyoo-lur
dih-jeh-nuh-ray-shun) is a gradual and progressive deterioration of the macula,
the most sensitive region of the retina. The condition leads to progressive
loss of central vision (the ability to see fine details directly in front).
Macular degeneration is often age related (it occurs in older people,
especially older than 60), but sometimes it can occur in younger people.
Excessive exposure to sunlight and smoking can increase the risk for
age-related macular degeneration. Symptoms may include increased difficulty
reading or watching TV, or distorted vision in which straight lines appear wavy
or objects look larger or smaller than normal.
Trachoma (pronounced: truh-ko-muh) occurs when a very contagious
microorganism called Chlamydia trachomatis causes inflammation in the
eye. It's often found in poor rural countries that have overcrowded living
conditions and limited access to water and sanitation. Blindness due to
trachoma has been virtually eliminated from the USA.
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