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Double vision can have many different causes, but it
is important to distinguish between double vision seen with one eye
alone, as opposed to that seen with both eyes at the same time. In other
words, if the double vision disappears when one or the other eye is
closed, it is due to a misalignment between the two eyes. Most of the
topics on this page discuss these misalignment problems. When the double
vision is present even with one eye closed, it may be due to optical
problems with the eye, or refractive problems. This can come from improper
glasses prescriptions, cataract, or corneal scars.
For eye anatomy explanations, go to
- Strabismus is a term that can be used to describe
any ocular misalignment, but most commonly it refers to a group of
conditions of ocular misalignment not due to any specific cause.
Instead, the eyes turn in or out on their own, not due to muscle
paralysis, trauma, or other cause. Usually these conditions occur in
childhood, and can signal or lead to the development of a "lazy eye",
or amblyopia. During the early years of development of the visual
system (from birth to around age 8 to 9), anything which interferes
with a clear image being received by an eye can lead to subnormal
development of the entire visual system serving that eye. If this
problem is not corrected, irreversible visual loss can occur
(amblyopia). While many things can cause amblyopia (need for glasses
prescription, childhood cataract, retinal disorders, etc.),
misalignment of the eyes is a common cause or associated condition.
Thus, it is important to have a child of any age promptly examined by
an ophthalmologist if their is any evidence
of visual problem.
There are numerous types of strabismus. Some occur constantly, and
some are evident only occasionally (intermittant). Some misalignments
of the eyes occur mainly during times of fatigue, daydreaming, or
speaking. Strangely enough, strabismus does not commonly lead to complaints
of double vision. In young children, the visual system has mechanisms
to avoid double vision. If one eye turns in the wrong direction, the
central visual area of that eye is simply turned off (suppression).
In some conditions, a peculiar head position may be adopted by a person
that minimizes double vision. Some common types of strabismus include:
- Esotropia - or inturning of the eyes. This condition may occur
in very young infants (less than 1 year old), or may develop later
in childhood. In some cases farsightedness may lead to esotropia,
and in other cases the inturning may only occur with reading.
In these situations, the use of glasses, and possibly bifocals
may alleviate the problem. Amblyopia (lazy eye) must be constantly
searched for, and treated aggressively if found (patching of the
dominant eye). Sometimes eye muscle surgery can re-align the eyes
if other therapies are not effective.
- Exotropia - or outturning of the eyes. This condition can occur
in children, and may initially only be present occasionally (during
fatigue or daydreaming). It may progress to being present at distance
or near, and may become more constant. If not treated, it can
continue into adulthood, and the person's eye may continue to
wander out at times unknowingly. In children, any uncorrected
glasses presecription or amblyopia is treated prior to muscle
realignment surgery (if needed).
- Duane's syndrome is a fairly common ocular misalignment present
from birth. Usually, one eye or the other cannot turn in toward
the nose all of the way, and so double vision can develop in certain
positions of gaze. Children with this condition often adopt a
head turn away from the affected eye. Thus, the affected eye is
usually turned away from the nose, and the eyes stay properly
- Convergence insufficiency - this indicates a problem with the
natural inturning of the eyes that occurs with reading. People
with this problem have to struggle to keep the eyes aligned when
looking at something close. Often the eyes will separate apart
at some point, the text will seem to run together, and the reading
must be temporarily stopped. This is a common cause of "eyestrain",
and can also be seen in people with certain neurological problems,
such as Parkinson's disease. Treatment can sometimes involve glasses,
holding reading material further away, and possibly "eye
exercises". This is one condition that can be helped by orthoptics,
or vision training, since the ability of the eyes to turn in can
An infection of the orbit, or boney eye socket,
can lead to severe symptoms, one of which is double vision.
Usually orbital infection spreads from adjacent sinuses, and
sometimes from a skin or eyelid infection. Symptoms include
pain, eyelid swelling and possibly a lump behind the eyelids
that can be felt, eye and eyelid redness, discharge, blurred
vision, eye displacement or protrusion, and double vision. The
double vision comes from the infection preventing normal movement
of the eye, and a misalignment may occur in certain positions
of gaze. People with this condition are usually treated in the
hospital with IV antibiotics. Diabetics are subject to a particularly
severe and destructive fungal orbital cellulitis.
NOTE: A tumor of the orbit can cause similar symptoms, although
usually with less pain, redness, and discharge. A condition known
as orbital pseudotumor ("like a tumor") is an inflammatory
condition which can simulate tumor or infection, but usually responds
to steroids. A CT scan or MRI is usually done in cases of orbital
infection, tumor, or pseudotumor to help make the diagnosis and
- There are three nerves which control the six "extra-ocular
muscles" of each eye, or the muscles that control eye movement.
These nerves are called "cranial nerves", since they come
directly from the brain rather than the spinal cord. There are twelve
cranial nerves, and they are often named by a number 1 through 12.
(Note: the optic nerve is cranial nerve number two). These nerves
pass under the brain to enter the orbit on each side, until they reach
the muscles that they control. Damage to these nerves leads to paralysis
of the muscles that they control. There are four muscles which control
the movement of the eye roughly up, down, left, and right, although
it is really more complicated than that. Two additional muscles (the
"oblique" muscles, control some up and down movement, as
well as the twisting or tilting movement of the eyes).
- Paralysis of Cranial Nerve number Three: The third cranial nerve
controls four of the six eye muscles, as well as the abilitiy
of the eye to focus and pupil to constrict. The muscle that is
controls turn the eye up, down, and in. Paralysis of this nerve
leads to the affected eye being unable to turn in, and it is often
turned out and down. The pupil may or may not be dilated as well.
Causes of this condition can be serious, such as an expanding
aneurysm on an artery at the base of the brain, or tumor. Stroke
can also cause dysfunction of this nerve. In some cases, people
with diabetes and other vascular disease can develop a temporary
paralysis of this nerve that resolves over a period of a few months.
Often the pupil is not affected in the diabetic type of paralysis.
A third cranial nerve paralysis is usually treated an an emergency.
- Paralysis of Cranial Nerve number Four: The forth cranial nerve
controls only one eye muscle, the "superior oblique muscle".
This muscle is involved in the twisting or rotation of the eye,
and somewhat in downgaze (especially when also looking in). Paralysis
of this nerve can give variable symptoms. Sometimes people will
notice double vision on in some extreme position of gaze. Others
may develop a more severe vertical double vision (things separated
up and down), often with a tilted effect as well. This nerve is
particularly prone to damage from head trauma, sometimes even
just a bad bump on the head. Vascular problems such as diabetes
can rarely cause this as well. Prisms placed in glasses can usually
reduce double vision until the nerve function returns.
- Paralysis of Cranial Nerve number Six: The sixth cranial nerve
controls the muscle that turns the eye outward. Thus, is paralyzed,
the eye will turn inward, and often cannot often cross the midline
back toward the outside. This leads to severe horizontal double
vision (side to side), usually bad enough to require patching
of one eye to prevent the double vision. This is commonly caused
by vascular problems such as diabetes, and the nerve function
returns in 1 to 3 months. Other problems such as tumor, temporal
arteritis, and stroke can cause this as well.
- Thyroid dysfunction can affect the tissues around the eye and in
the orbit in a condition called "thyroid related orbitopathy".
Usually this is associated with hyperthyroidism (over-acting thyroid)
as in "Grave's disease", although it can occur in a normal
or even under-acting thyroid. It is felt to be an auto-immune problem
where the immune system attacks the tissues around the eye, and possibly
also the thyroid gland. This leads to a variety of eye symptoms.
- Swelling of the eyelids and tissues around the eyes.
- Eyelid "retraction", or excessive opening. This leads
to a wide-open eye staring appearance. The white of the eye is
often visible above and below the iris.
- Eye protrusion, where swelling of the tissues in the orbit behind
the eye literally push the eye outward.
- Corneal drying and breakdown can occur from exposure of the
cornea due to the eye protrusion and eyelid opening.
- Double vision can occur due to swelling and dysfunction of the
eye muscles. Especially involved are the muscle the turn the eye
downward. Thus, the eye becomes tethered and has difficulty looking
upward, especially when turned out also. Double vision due to
misalignment of the eyes occurs in certain positions of gaze,
and it usually is a vertical double vision. It may be highly variable.
- Compression of the optic nerve in the orbit due to the swelling
of the eye muscles can lead to visual loss, blind spots in the
vision, loss of color vision, and swelling of the optic nerve.
This can be an ophthalmic emergency and may take high dose steroids
or surgery to reverse.
Thyroid related eye problems tend to come and go, and the eyes
may remain unaffected for long periods of time between attacks.
Supportive treatment during symptomatic periods such as eye lubrication
and steroids to reduce swelling may help.
||Blunt trauma to the eye and bones around the eye
(such as by a fist) can lead to a fracture in the thin bones
of the orbit behind the eye. Anyone with such injury should
seek out a complete eye examination to rule out any other eye
injury promptly. The floor and inside wall of the orbit are
especially thin, and sinuses are on the other side of the bone.
Blunt trauma can cause what is termed a "blow-out fracture",
where the sudden rise in pressure in the orbit literally blows
a fracture through the bone and into the sinus. If this involves
the floor of the orbit, the cheek below the eye and upper gums
in the mouth can often become numb due to damage to a sensory
nerve that runs in the floor of the orbit.
If the fracture of large enough, the contents of the orbit can start
to slip into the sinus, and the eye will appear to sink backwards.
Sometimes an eye muscle can get trapped in an orbital fracture and
become stuck. This leads to double vision especially if looking up,
with pain. A CT scan of the orbit can diagnose fractures and entrapment
of muscles. Entrapped muscles often have to be released surgically.
Antibiotics are usually given after an orbital fracture, due to risk
of infection from the sinus into the orbit.
- An uncorrected glass prescription, especially if nearsighted or
with astigmatism, can lead to ghost images or slight double vision.
Unlike double vision caused by misalignment of the eyes, this type
of double vision remains if one eye is closed. It is often worse at
night when the pupil dilates some.
Irregular astigmatism, or an uneven curvature of the cornea, can
lead to ghost images which may only be treatable using a contact
Certain types of cataract can lead to double vision due to distortion
of images passing through the lens of the eye, and from glare. Intraocular
lens implants can cause double vision if they slip out of position
(rare), and the edge of the lense comes close to the pupil center.
Some people after glaucoma or cataract surgery have an iridectomy
done at the time of surgery. This is a hole cut into the iris usually
hidden by the upper eyelid. In some with an iridectomy, double vision
may occur with light passing through this opening.