Double Vision
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Diplopia is the simultaneous
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system, ...
of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often voluntary. However, when occurring involuntarily, it results in impaired function of the
extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the ot ...
, where both eyes are still functional, but they cannot turn to target the desired object. Problems with these muscles may be due to mechanical problems, disorders of the
neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation ...
, disorders of the
cranial nerves Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and ...
(
III III or iii may refer to: Companies * Information International, Inc., a computer technology company * Innovative Interfaces, Inc., a library-software company * 3i, formerly Investors in Industry, a British investment company Other uses * Ins ...
, IV, and VI) that
innervate A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
the muscles, and occasionally disorders involving the supranuclear oculomotor pathways or ingestion of
toxins A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...
. Diplopia can be one of the first signs of a
systemic disease A systemic disease is one that affects a number of organs and tissues, or affects the body as a whole. Examples * Mastocytosis, including mast cell activation syndrome and eosinophilic esophagitis * Chronic fatigue syndrome * Systemic va ...
, particularly to a muscular or neurological process, and it may disrupt a person's balance, movement, or reading abilities.


Causes

Diplopia has a diverse range of ophthalmologic, infectious, autoimmune, neurological, and neoplastic causes: *
Papilledema Papilledema or papilloedema is optic disc swelling that is caused by increased intracranial pressure due to any cause. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare. In ...


Diagnosis

Diplopia is diagnosed mainly by information from the patient. Doctors may use blood tests, physical examinations,
computed tomography A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
(CT), or magnetic resonance imaging (MRI) to find the underlying cause. Classification One of the first steps in diagnosing diplopia is often to see whether one of two major classifications may be eliminated. That involves blocking one eye to see which symptoms are evident in each eye alone. Persisting blurry or double vision with one eye closed is classified as monocular diplopia.


Binocular

Binocular diplopia is double vision arising as a result of
strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...
(in layman's terms "cross-eyed"), the misalignment of the two eyes relative to each other, either
esotropia Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usua ...
(inward) or
exotropia Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotrop ...
(outward). In such a case while the
fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy * Fovea centralis of the retina * Fovea buccalis or Dimple * Fovea of the femoral head *Trochlear fovea of the f ...
of one eye is directed at the object of regard, the fovea of the other is directed elsewhere, and the image of the object of regard falls on an extrafoveal area of the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
. Acute diplopia is a diagnostic challenge. The most common cause of acute diplopia are ocular motor nerve palsies (OMP). The brain calculates the visual direction of an object based upon the position of its image relative to the fovea. Images falling on the fovea are seen as being directly ahead, while those falling on retina outside the fovea may be seen as above, below, right, or left of straight ahead depending upon the area of retina stimulated. Thus, when the eyes are misaligned, the brain perceives two images of one target object, as the target object simultaneously stimulates different, noncorresponding, retinal areas in either eye, thus producing double vision. This correlation of particular areas of the retina in one eye with the same areas in the other is known as retinal correspondence. This relationship also gives rise to an associated phenomenon of binocular diplopia, although one that is rarely noted by those experiencing diplopia. Because the fovea of one eye corresponds to the fovea of the other, images falling on the two foveae are projected to the same point in space. Thus, when the eyes are misaligned, two different objects will be perceived as superimposed in the same space. This phenomenon is known as visual confusion'. The brain naturally guards against double vision. In an attempt to avoid double vision, the brain can sometimes ignore the image from one eye, a process known as suppression. The ability to suppress is to be found particularly in childhood when the brain is still developing. Thus, those with childhood strabismus almost never complain of diplopia, while adults who develop strabismus almost always do. While this ability to suppress might seem an entirely positive adaptation to strabismus, in the developing child, this can prevent the proper development of vision in the affected eye, resulting in
amblyopia Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. It results in decreased vision in an eye that typically appears normal in other aspects. Amb ...
. Some adults are also able to suppress their diplopia, but their suppression is rarely as deep or as effective and takes much longer to establish, thus they are not at risk of permanently compromising their vision. In some cases, diplopia disappears without medical intervention, but in other cases, the cause of the double vision may still be present. Certain people with diplopia who cannot achieve fusion and yet do not suppress may display a certain type of spasm-like irregular movement of the eyes in the vicinity of the fixation point (see: Horror fusionis).


Monocular

Diplopia can also occur when viewing with only one eye; this is called monocular diplopia, or where the patient perceives more than two images, monocular polyopia. While serious causes rarely may be behind monocular diplopia symptoms, this is much less often the case than with binocular diplopia. The differential diagnosis of multiple image perception includes the consideration of such conditions as corneal surface
keratoconus Keratoconus (KC) is a disorder of the eye that results in progressive thinning of the cornea. This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, and light sensitivity leading to poor quality-of-life. U ...
,
subluxation A subluxation is an incomplete or partial dislocation of a joint or organ. According to the World Health Organization (WHO), a subluxation is a "significant structural displacement", and is therefore always visible on static imaging studies, su ...
of the lens, a structural defect within the eye, a lesion in the anterior
visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
, or nonorganic conditions, but diffraction-based (rather than geometrical) optical models have shown that common optical conditions, especially
astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at ni ...
, can also produce this symptom.


Temporary

Temporary binocular diplopia can be caused by
alcohol intoxication Alcohol intoxication, also known as alcohol poisoning, commonly described as drunkenness or inebriation, is the negative behavior and physical effects caused by a recent consumption of alcohol. In addition to the toxicity of ethanol, the main ...
or head injuries, such as
concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include loss of consciousness (LOC); memory loss; headaches; difficulty with thinking, concentratio ...
(if temporary double vision does not resolve quickly, one should see an
optometrist Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities. Optometrists are health care professionals who typically provide comprehensive primary eye care. In the Un ...
or
ophthalmologist Ophthalmology ( ) is a surgery, surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Followin ...
immediately). It can also be a side effect of
benzodiazepines Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, ...
or
opioids Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid us ...
, particularly if used in larger doses for recreation, the antiepileptic drugs
phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence seizures. The intr ...
and zonisamide, and the anticonvulsant drug
lamotrigine Lamotrigine, sold under the brand name Lamictal among others, is a medication used to treat epilepsy and stabilize mood in bipolar disorder. For epilepsy, this includes focal seizures, tonic-clonic seizures, and seizures in Lennox-Gastaut syn ...
, as well as the hypnotic drug zolpidem and the dissociative drugs
ketamine Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a recreational drug. It is one of the safest anesthetics, as, in contrast with opiates, ether, and propofol, it suppresses ...
and
dextromethorphan Dextromethorphan (DXM) is a medication most often used as a cough suppressant in over-the-counter cold and cough medicines. It is sold in syrup, tablet, spray, and lozenge forms. In 2022, the FDA approved a formulation of it combined with bu ...
. Temporary diplopia can also be caused by tired or strained eye muscles. If diplopia appears with other symptoms such as fatigue and acute or chronic pain, the patient should see an ophthalmologist immediately.


Voluntary

Some people are able to consciously uncouple their eyes, either by overfocusing closely (i.e. going cross-eyed) or unfocusing. Also, while looking at one object behind another object, the foremost object's image is doubled (for example, placing one's finger in front of one's face while reading text on a computer monitor). In this sense, double vision is neither dangerous nor harmful, and may even be enjoyable. It makes viewing stereograms possible. Monocular diplopia may be induced in many individuals, even those with normal eyesight, with simple defocusing experiments involving fine, high-contrast lines.


Treatment

The appropriate treatment for binocular diplopia depends upon the cause of the condition producing the symptoms. Efforts must first be made to identify and treat the underlying cause of the problem. Treatment options include eye exercises, wearing an eye patch on alternative eyes, prism correction, and in more extreme situations, surgery or
botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromu ...
. If diplopia turns out to be intractable, it can be managed as last resort by obscuring part of the patient's field of view. This approach is outlined in the article on diplopia occurring in association with a condition called horror fusionis.


See also

*
Binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...
*
Monocular rivalry Monocular rivalry is a phenomenon of human visual perception that occurs when two different images are optically superimposed. During prolonged viewing, one image becomes clearer than the other for a few moments, then the other image becomes clear ...
*
Orthoptics Orthoptics is a profession allied to the eye care profession. Orthoptists are the experts in diagnosing and treating defects in eye movements and problems with how the eyes work together, called binocular vision. These can be caused by issues with ...


References


Further reading

*


External links


Deciphering Diplopia
{{Eye pathology Visual disturbances and blindness Vision