What Causes Low Vision?
Several eye diseases may be responsible for low vision, including:
Macular Degeneration – A disorder that
affects the retina, the light sensitive lining at the back of the eye where
images are focused. The macula—the area on the retina responsible for sharp
central vision—deteriorates, gradually causing blurred vision, difficulty
reading, and finally, a blind spot in the central area of vision. This is known
as the "dry" form of macular degeneration, is age-related, and the leading cause
of blindness in people over 50, with some 13 million of the U.S. population
affected. The exact cause is unknown, but may be related to smoking, and
possibly long-term exposure to high levels of the sun's ultraviolet radiation
and blue light. More rapid and severe vision loss comes from the "wet" form,
when abnormal blood vessels develop under the macula and leak fluid and blood.
There are also juvenile forms which are hereditary.
Diabetic Retinopathy – Diabetes can cause
blood vessels that nourish the retina to leak, develop brush-like branches or
enlarge. This can interfere with vision and, over time, may destroy the retina.
Laser procedures and surgical treatments are used to reduce its progression.
Retinitis Pigmentosa – Gradually destroys night vision, severely reduces side
vision, and may result in total blindness. An inherited disease, it usually
produces its first symptom—night blindness—in childhood or adolescence.
Retrolental Fibroplasia (retinopathy of prematurity) – Occurs in infants
born prematurely and, in some cases, is caused by high oxygen levels in
incubators during the first 10 days of life.
Retinal Detachment – Can result in total blindness in the detached area of
the affected eye. It involves the retina separating from its underlying layer.
Causes are holes in the retina, eye trauma, infection, blood vessel disturbance
or a tumor. Through early diagnosis, most detached retinas can be surgically
re-attached with partial restoration of vision.
Cataracts – A clouding of part or all of the
lens inside the eye. This prevents light from reaching the retina at the back of
the eye, resulting in a generalized loss of vision. Causes are aging, long-term
exposure to the sun's ultraviolet radiation, injury, disease and inherited
disorders. If the eye is healthy, the cataract can be surgically removed and
vision restored, usually with intraocular lens implants. Cataract surgery has a
high success rate but a small number of those for whom it is not successful will
require low vision care.
Glaucoma – The internal pressure in the eye
builds up because of problems with the flow or drainage of fluid within the eye,
damaging the optic nerve and causing partial or total loss of sight. There are
no early symptoms in the most common form, but the first signs of damage are
side vision defects. Early diagnosis and treatment with drugs or sometimes
surgery can minimize vision loss.
Vision can also be lost or damaged as a result of head injuries, brain damage
and strokes.
