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OCULAR SYMPTOMS
Floaters, Flashing, Rainbows, Abnormal Color Vision,
Distorted Vision
Contents of this Page
Introduction: Floaters,
Flashing lights, Rainbows, Abnormal Color Vision, Distorted Vision
This page discusses unusual visual phenomenon such as floaters and
different types of flashing lights. Other visual abnormalities such
as seeing rainbows around lights, abnormal color vision, and distorted
vision are discussed as well.
The first grouping of abnormalities give symptoms of
floaters or flashing lights. Separate sections
on Rainbows,
Abnormal Color Vision, Distorted
Vision, and Tunnel Vision follow.
Conditions:
For eye anatomy explanations, go to
ANATOMY
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The vitreous is a gel-like fluid which fills most
of the eye. As people age, this vitreous becomes more and more
liquefied. The vitreous has loose attachments to the retina,
and more firm attachments to the optic nerve. At some point
in a person's life, the vitreous liquefies enough to shift position
in the eye. When this occurs, usually between age 50 and 70,
the back edge of the vitreous will pull forward away from the
retina, leading to a "vitreous detachment". This is
generally a normal process, although it may happen abnormally
early in cases of high nearsightedness or trauma. As the vitreous
detaches, it tugs on the retina. This is perceived as a flash
of light, similar to a lightning flash in the corner of the
vision. It may occur especially with eye movement, since the
vitreous moves in the eye. Debris pulled off of the optic nerve
and retina are then seen as floaters, suspended in the vitreous
above the retina. Sometimes this is described as a cobweb, a
net, a string, or a fly over the vision.
These symptoms usually resolve over a period of days to weeks, although
some people will continue to see the floaters for a longer period
of time. The important thing is to determine that the retina is healthy
as the vitreous detaches. This requires a careful dilated examination
of the retina to look for tears, or other areas which may be at risk
for tearing. A retinal tear can then lead to retinal detachment, if
not treated. Thus, people experiencing these symptoms should be examined
by an ophthalmologist as soon as possible. (Note, only about 1 in
10,000 cases of vitreous detachment lead to retinal detachment, but
it still is one of the most common causes of retinal detachment.)
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A tear in the retina can occur with vitreous detachment
(see discussion above), with trauma or eye injury, or in areas
at risk for a retinal tear, such as "lattice degeneration".
The symptoms of a retinal tear usually are of a flash of light
in the peripheral vision followed by floaters. The floaters
may be debris, but may also be blood, if the tear extends through
a retinal blood vessel. Symptomatic retinal tears should be
treated by laser to prevent
retinal
detachment. Sometimes a retinal tear is discovered incidentally
as part of an eye examination. These may or may not need to
be treated. |
- Uveits refers to a large group of disorders which cause inflammation
within the eye. A similar condition,
iritis,
usually refers to an inflammation involving the front structures of
the eye associated with pain, redness, and sensitivity to light. In
this discussion, uveitis could have these symptoms, but mainly consists
of inflammation involving the back structures of the eye (the retina,
choroid, and optic nerve). Inflammatory debris liberated into the
vitreous leads to the visualization of floaters. If this liberation
continues, the vision may become substantially hazy and blurred.
There are numerous conditions leading to uveitis, and many have
floaters and blurred vision as predominant symptoms: sarcoidosis,
toxoplasmosis chorioretinitis, ocular histoplasmosis, multifocal
choroiditis, pars planitis, endophalmitis, syphillis, candidiasis,
viral uveitis, Vogt-Koyanagi-Harada syndrome, and
HIV
related unveitis.
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- The entopic phenomenon is a normal phenomenon that some people
may become suddenly aware of. This sudden awareness may lead to the
idea that there is a problem with the eyes, when actually there is
not. The entopic phenomenon can be seen especially when looking at
a bright blue sky. Small, rapid pin-point sparks of light can be seen
darting about in the central vision. Some people may think that these
sparks are floaters. In reality, they represent white blood cells
moving through the blood capillaries of the retina. This is a normal
finding, and actually may indicate normal retinal function.
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Migraine headaches may be preceded by a visual
"aura", lasting for 20 to 30 minutes, and then proceeding
to the headache. Some people, however, experience the aura but
do not have a headache. This visual aura can be very dramatic.
Classically, a small blind spot appears in the central vision
with a shimmering, zig-zag light inside of it. This enlarges,
and moves to one side or the other of the vision, over a 20
to 30 minute period. When it is large, this crescent shaped
blind spot containing this brightly flashing light can be difficult
to ignore, and some people fear that they are having a stroke.
In reality, it is generally a harmless phenomenon, except in
people who subsequently get the headache of migraine. Since
migraine originates in the brain, the visual effect typically
involves the same side of vision in each eye, although it may
seem more prominent in one eye or the other.
Some people get different variations of this phenomenon, with the
central vision being involved, or with the visual effect similar to
"heat rising off of a car". Some people describe a "kaleidoscope"
effect, with pieces of the vision being missing. All of these variations
are consistent with ophthalmic migraine.
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- Seeing rainbows around lights, especially at night, usually indicates
swelling of the cornea. This may occur from a variety of causes which
are discussed under
Corneal
Edema. Cataract can sometimes cause this also.
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| Colour vision is perceived mainly by the macula,
which is the central vision portion of the retina. Thus any
disorder affecting the macula may cause a disturbance in color
vision. However, about 8% of males and 0.5% of females have
some version of "colour blindness" from birth. Usually
this is an genetically inherited trait, and is of the "red-green
confusion" variety. The reds, browns, olives, and gold
may be confused. Purple may be confused with blue, and pastel
pinks, oranges, yellows, and greens look similar. Usually both
eyes are affected equally. |
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There are many obscure macular retinal disorders that can lead to
a loss of colour vision, and many of these syndromes are inherited
as well. There may also be a problem with a generalized loss of vision
with these problems as well. Other retinal problems can lead to a
temporary disturbance of colour vision, such as
Central
serous chorioretinopathy,
Macular
Edema of different causes,
Macular Degeneration and
Epiretinal
membrane.
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Certain types of cataract can gradually affect the colour vision,
but this is usually not noticed until one cataract is removed. The
cataract seems to filter out the colour blue, and everything seems
more blue after cataract extraction. Optic nerve disorders such
as
Optic
Neuritis can greatly affect colour vision, with colours seeming
washed out during or after an episode.
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- Distortion of vision refers to straight lines not appearing straight,
but instead bent, crooked, or wavy. Usually this is caused by distortion
of the retina itself. This distortion can herald a loss of vision
in
macular
degeneration, so anyone with distorted vision should seek medical
attention by an ophthalmologist promptly. Other conditions leading
to swelling of the retina can cause this distortion, such as
Macular
edema and
Central
serous chorioretinopathy.
An "Amsler grid" can be supplied by an ophthalmologist
so that the vision can be monitored for distortion in people who
may be predisposed to this problem.
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- "Tunnel vision" implies that the peripheral vision, or
side vision, is lost, while the central vision remains. Thus, the
vision is like looking through a tunnel, or through a paper towel
roll. Some disorders that can cause this include:
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Glaucoma
- severe glaucoma can result in loss of nearly all of the
peripheral vision, with a small "island" of central
vision remaining. Sometimes even this island of vision can be
lost as well.
- Retinitis pigmentosa - This is usually a hereditary disorder
which can be part of numerous syndromes. It is more common in
males. The peripheral retina develops pigmentary deposits, and
the peripheral vision gradually becomes worse and worse. The central
vision can be affected eventually as well. People with this problem
may have trouble getting around in the dark. Cataract can be a
complication as well. There is no known treatment for this disorder,
and supplements of Vitamin A have not been proven to help.
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Stroke
- a stroke involving both sides of the visual part of the
brain may wipe out nearly all of the peripheral vision. Fortunately,
this is a very rare occurrence
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