Optic Neuritis
The retina lies
in the back of the eye and is a multi-layered tissue which detects
visual images. These images are transmitted to the brain through
approximately 1 million tiny nerve fibers. These nerve fibers
converge in the back of the eye, before going to the brain, into
a bundle called the optic nerve. If some or all of the nerve
fibers are damaged, visual capability deteriorates.
When the optic nerve becomes inflamed, this condition is called
optic neuritis. The nerve tissue becomes swollen and red, and
the nerve fibers do not work properly. If many of the nerve fibers
are involved, the vision may be dramatically affected, but if
the optic neuritis is mild, vision is nearly normal. Optic neuritis
can be caused by many diseases and conditions and may affect
the optic nerve of one or both eyes.
Some people, especially children, develop optic neuritis following
a virus illness such as mumps, measles, or a cold. In others,
optic neuritis may occur as a sign of a neurologic disease affecting
nerves in various parts of the body, such as multiple sclerosis.
In a rare condition called Leber's optic neuropathy, which often
runs in families, a special kind of optic neuritis may appear
in both eyes within a short span of time. Most of the time, however,
the cause for optic neuritis is unknown. In those cases, the
eye disorder is called neuritis idiopathic, meaning that no particular
cause can be found.
Optic neuritis usually comes on suddenly, and the patient notices
vision is blurred in one or both eyes. The vision is dim, like
somebody turned down the lights, and colors may appear to be
washed out. There may be pain in the area of the eye socket,
especially when moving the eyes. The vision may continue to get
worse over a week or two, and may seem worse after exercising
or a hot bath.
A careful description of these symptoms is important to your
doctor for the diagnosis of optic neuritis. The optic nerve enters
the back of the eye where it appears as a small disc. Your eye
doctor can examine the optic nerve inside the eye by using a
special instrument called an ophthalmoscope. Swelling of the
optic nerve may or may not be visible. If the optic nerve inflammation
occurs inside the eye, it can be readily detected. If swelling
of the nerve occurs behind the eye, the doctor may not be able
to see the swollen nerve tissue.
Since optic neuritis can be confused with many other causes of
poor vision, an accurate medical diagnosis is important. Ultrasound,
CT scans or visual brain wave recordings might be ordered. Other
tests which may be performed include color vision, side vision,
and pupil reactions to light.
Unfortunately, there is no good treatment for optic neuritis.
Cortisone-like medications (steroids) can be prescribed, but
in most cases they are not effective. In many cases, patients
with optic neuritis improve without treatment. The vision may
return to normal or, in some cases, good but incomplete improvement
occurs. A few patients fail to recover normal vision, especially
those with special conditions.
