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OCULAR SYMPTOMS

Double Vision

Contents of this Page

Introduction: Double Vision

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.

Conditions:

For eye anatomy explanations, go to ANATOMY

Strabismus

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 aligned.
  • 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 be improved.


Orbital Infection (cellulitis)


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 guide treatment.

Eye Muscle Paralysis

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 Disease

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.

Orbital Fracture

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.


Refractive Error

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 lens.

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.

 

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