Diplopia

Diplopia is double vision—seeing one object as two. This symptom results when extraocular muscles fail to work together, causing images to fall on noncorresponding parts of the retinas. What causes this muscle incoordination? Orbital lesions, the effects of surgery, or impaired function of the cranial nerves that supply extraocular muscles—oculomotor (CN III), trochlear (CN IV), and abducens (CN VI)—may be responsible. (See Testing extraocular muscles, page 246.)

Diplopia usually begins intermittently and affects near or far vision exclusively. It can be classified as monocular or binocular. More common binocular diplopia may result from ocular deviation or displacement, extraocular muscle palsies, or psychoneurosis, or it may occur after retinal surgery. Monocular diplopia may result from an early cataract, retinal edema or scarring, iridodialysis, a subluxated lens, a poorly fitting contact lens, or an uncorrected refractive error such as astigmatism. Diplopia may also occur in hysteria or malingering.

History and physical examination

If the patient complains of double vision, first check his neurologic status. Evaluate his level of consciousness (LOC); pupil size, equality, and response to light; and motor and sensory function. Then take his vital signs. Briefly ask about associated symptoms. First find out about associated neurologic symptoms, especially a severe headache, because diplopia can accompany serious disorders.

Next, continue with a more detailed examination. Find out when the patient first noticed diplopia. Are the images side by side (horizontal), one above the other (vertical), or a combination? Does diplopia affect near or far vision? Does it affect certain directions of gaze? Ask if diplopia has worsened, remained the same, or subsided. Does its severity change throughout the day? Diplopia that worsens or appears in the evening may indicate myasthenia gravis. Find out if the patient can correct diplopia by tilting his head. If so, ask him to show you. (If the patient has a fourth cranial nerve lesion, tilting the head toward the opposite shoulder causes compensatory tilting of the unaffected eye. If he has incomplete sixth cranial nerve palsy, tilting the head toward the side of the paralyzed muscle may relax the affected lateral rectus muscle.)

Explore associated symptoms such as eye pain. Ask about hypertension, diabetes mellitus, allergies, and thyroid, neurologic, or muscular disorders. Also, note a history of extraocular muscle disorders, trauma, or eye surgery.

Observe the patient for ocular deviation, ptosis, exophthalmos, eyelid edema, and conjunctival injection. Distinguish monocular from binocular diplopia by asking the patient to occlude one eye at a time. If he still sees double out of one eye, he has monocular diplopia. Test visual acuity and extraocular muscles. Also, check vital signs.

Medical causes

Alcohol intoxication

Diplopia, a common symptom of this disorder, may be accompanied by confusion, slurred speech, halitosis, staggering gait, behavior changes, nausea, vomiting and, possibly, conjunctival injection.

Botulism

The hallmark signs of botulism are diplopia, dysarthria, dysphagia, and ptosis. Early findings include dry mouth, sore throat, vomiting, and diarrhea. Later, descending weakness or paralysis of extremity and trunk muscles causes hyporeflexia and dyspnea.

Brain tumor

Diplopia may be an early symptom of a brain tumor. Associated signs and symptoms vary with the tumor’s size and location but may include eye deviation, emotional lability, decreased LOC, headache, vomiting, absence or generalized tonic-clonic seizures, hearing loss, visual field deficits, abnormal pupillary responses, nystagmus, motor weakness, and paralysis.

Cavernous sinus thrombosis

This disorder may produce diplopia and limited eye movement. Associated signs and symptoms include exophthalmos, orbital and eyelid edema, diminished or absent pupillary responses, impaired visual acuity, papilledema, and fever.

Diabetes mellitus

Among the long-term effects of this disorder may be diplopia due to isolated third cranial nerve palsy. Diplopia typically begins suddenly and may be accompanied by pain.

Encephalitis

Initially, this disorder may cause a brief episode of diplopia and eye deviation. However, it usually begins with sudden onset of high fever, severe headache, and vomiting. As the inflammation progresses, the patient may display signs of meningeal irritation, decreased LOC, seizures, ataxia, and paralysis.

Head injury

Potentially life-threatening head injuries may cause diplopia, depending on the site and extent of the injury. Associated signs and symptoms include eye deviation, pupillary changes, headache, decreased LOC, altered vital signs, nausea, vomiting, and motor weakness or paralysis.

Intracranial aneurysm

This life-threatening disorder initially produces diplopia and eye deviation, perhaps accompanied by ptosis and a dilated pupil on the affected side. The patient complains of a recurrent, severe, unilateral, frontal headache. After the aneurysm ruptures, the headache becomes violent. Associated signs and symptoms include neck and spinal pain and rigidity, decreased LOC, tinnitus, dizziness, nausea, vomiting, and unilateral muscle weakness or paralysis.

Multiple sclerosis (MS)

Diplopia, a common early symptom of MS, is usually accompanied by blurred vision and paresthesia. As MS progresses, signs and symptoms may include nystagmus, constipation, muscle weakness, paralysis, spasticity, hyperreflexia, intention tremor, gait ataxia, dysphagia, dysarthria, impotence, emotional lability, and urinary frequency, urgency, and incontinence.

Myasthenia gravis

This disorder initially produces diplopia and ptosis, which worsen throughout the day. It then progressively involves other muscles, resulting in blank facial expression; nasal voice; difficulty chewing, swallowing, and making fine hand movements and, possibly, signs of life-threatening respiratory muscle weakness.

Ophthalmologic migraine

Most common in young adults, this disorder results in diplopia that persists for days after the headache resolves. Accompanying signs and symptoms include severe unilateral pain, ptosis, and extraocular muscle palsies. Irritability, depression, or slight confusion may also occur.

Orbital blowout fracture

This fracture usually causes monocular diplopia affecting the upward gaze. However, with marked periorbital edema, diplopia may affect other directions of gaze. This fracture commonly causes periorbital ecchymosis but doesn’t affect visual acuity, although eyelid edema may prevent accurate testing. Subcutaneous crepitation of the eyelid and orbit is typical. Occasionally, the patient’s pupil is dilated and unreactive, and he may have a hyphema.

Orbital cellulitis

Inflammation of the orbital tissues and eyelids causes sudden diplopia as well as eye deviation and pain, purulent drainage, eyelid edema, chemosis and redness, exophthalmos, nausea, and fever.

Orbital tumor

An enlarging tumor can cause diplopia, exophthalmos and, possibly, blurred vision.

Stroke

Diplopia characterizes this life-threatening disorder when it affects the vertebrobasilar artery. Other signs and symptoms include unilateral motor weakness or paralysis, ataxia, decreased LOC, dizziness, aphasia, visual field deficits, circumoral numbness, slurred speech, dysphagia, and amnesia.

Thyrotoxicosis

Diplopia occurs when exophthalmos characterizes the disorder. It usually begins in the upper field of gaze because of infiltrative myopathy involving the inferior rectus muscle. It’s accompanied by impaired eye movement, excessive tearing, eyelid edema and, possibly, inability to close the eyelids. Other cardinal findings include tachycardia, palpitations, weight loss, diarrhea, tremors, an enlarged thyroid, dyspnea, nervousness, diaphoresis, and heat intolerance.

Transient ischemic attack (TIA)

A TIA, which may be a warning sign of a future stroke, is generally accompanied by diplopia, dizziness, tinnitus, hearing loss, and numbness. It can last for a few seconds or up to 24 hours.

Other causes

Eye surgery

Fibrosis associated with eye surgery may restrict eye movement, resulting in diplopia.

Special considerations

Continue to monitor vital signs and neurologic status if you suspect an acute neurologic disorder. Prepare the patient for neurologic tests such as a computed tomography scan. Provide a safe environment. If the patient has severe diplopia, remove sharp obstacles and assist him with ambulation. Also, institute seizure precautions if indicated.

Pediatric pointers

Strabismus, which can be congenital or acquired at an early age, produces diplopia; however, diplopia is a rare complaint in young children because the brain rapidly compensates for double vision by suppressing one image. School-age children who complain of double vision require a careful examination to rule out serious disorders such as a brain tumor.

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Book Source Details

• Book Title: Professional Guide to Signs & Symptoms (Fifth Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Professional Guide to Signs & Symptoms (Fifth Edition), Copyright © 2006 Lippincott Williams & Wilkins.

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