Ocular deviation

Ocular deviation: Excerpt from Signs & Symptoms: A 2-in-1 Reference for Nurses

Ocular deviation refers to abnormal eye movement that may be conjugate (both eyes move together) or disconjugate (one eye moves separately from the other). This common sign may result from ocular, neurologic, endocrine, and systemic disorders that interfere with the muscles, nerves, or brain centers governing eye movement. Occasionally, it signals a life-threatening disorder such as a ruptured cerebral aneurysm.

Normally, eye movement is directly controlled by the extraocular muscles innervated by the oculomotor, trochlear, and abducens nerves (cranial nerves III, IV, and VI). Together, these muscles and nerves direct a visual stimulus to fall on corresponding parts of the retina. Disconjugate ocular deviation may result from unequal muscle tone (nonparalytic strabismus) or from muscle paralysis associated with cranial nerve damage (paralytic strabismus). Conjugate ocular deviation may result from disorders that affect the centers in the cerebral cortex and brain stem responsible for conjugate eye movement. Typically, such disorders cause gaze palsy — difficulty moving the eyes in one or more directions.

Emergency Actions

If the patient displays ocular deviation, take his vital signs immediately and assess him for altered level of consciousness (LOC), pupil changes, motor or sensory dysfunction, and severe headache. If possible, ask the patient’s family about behavioral changes. Is there a history of recent head trauma? Respiratory support may be necessary. Also, prepare the patient for emergency neurologic tests such as a computed tomography scan.

History

If the patient isn’t in distress, find out how long he has had the ocular deviation. Is it accompanied by double vision, eye pain, or headache? Also, ask if he has noticed any associated motor or sensory changes, or fever.

Check for a history of hypertension, diabetes, allergies, and thyroid, neurologic, or muscular disorders. Then obtain a thorough ocular history. Has the patient ever had extraocular muscle imbalance, eye or head trauma, or eye surgery?

Physical assessment

Perform a complete neurologic assessment, including a complete eye assessment. During the physical assessment, observe the patient for partial or complete ptosis. Does he spontaneously tilt his head or turn his face to compensate for ocular deviation? Check for eye redness or periorbital edema. Assess visual acuity; then evaluate extraocular muscle function by testing the six cardinal fields of gaze. (See Testing the six cardinal positions of gaze.)

Medical causes

Brain tumor

The nature of ocular deviation depends on the site and extent of the tumor. Associated signs and symptoms include headaches that are most severe in the morning, behavioral changes, memory loss, dizziness, confusion, vision loss, motor and sensory dysfunction, aphasia and, possibly, signs of hormonal imbalance. The patient’s LOC may slowly deteriorate from lethargy to coma. Late signs include papilledema, vomiting, increased systolic blood pressure, widening pulse pressure, and decorticate posture.

Cerebral aneurysm

When an aneurysm near the internal carotid artery compresses the oculomotor nerve, it may produce features that resemble third cranial nerve palsy. Typically, ocular deviation and diplopia are the presenting signs. Other cardinal findings include ptosis, a dilated pupil on the affected side, and a severe, unilateral headache, usually in the frontal area. Rupture of the aneurysm abruptly intensifies the pain, which may be accompanied by nausea and vomiting. Bleeding from the site causes meningeal irritation, resulting in nuchal rigidity, back and leg pain, fever, irritability, occasional seizures, and blurred vision. Other signs and symptoms associated with intracranial bleeding include hemiparesis, dysphagia, and visual defects.

Diabetes mellitus

A leading cause of isolated third cranial nerve palsy, especially in the middle-age patient with long-standing mild diabetes, diabetes mellitus may cause ocular deviation and ptosis. Typically, the patient also complains of sudden onset of diplopia and pain.

Encephalitis

Encephalitis causes ocular deviation and diplopia in some patients. Typically, it begins abruptly with fever, headache, and vomiting, followed by signs of meningeal irritation (for example, nuchal rigidity) and of neuronal damage (for example, seizures, aphasia, ataxia, hemiparesis, cranial nerve palsies, and photophobia). The patient’s LOC may rapidly deteriorate from lethargy to coma within 24 to 48 hours after onset.

Head trauma

The nature of ocular deviation depends on the site and extent of head trauma. The patient may have visible soft-tissue injury, bony deformity, facial edema, and clear or bloody otorrhea or rhinorrhea. Besides these obvious signs of trauma, he may also develop blurred vision, diplopia, nystagmus, behavioral changes, headache, motor and sensory dysfunction, and a decreased LOC that may progress to coma. Signs of increased intracranial pressure — such as bradycardia, increased systolic pressure, and widening pulse pressure — may also occur.

Multiple sclerosis

Ocular deviation may be an early sign of multiple sclerosis. Accompanying it are diplopia, blurred vision, and sensory dysfunction such as paresthesia. Other signs and symptoms include nystagmus, constipation, muscle weakness, paralysis, spasticity, hyperreflexia, intention tremor, gait ataxia, dysphagia, dysarthria, impotence, and emotional instability. In addition, the patient may experience urinary frequency, urgency, and incontinence.

Myasthenia gravis

With myasthenia gravis, ocular deviation may accompany the more common presenting signs of diplopia and ptosis. This disorder may affect only the eye muscles, or it may progress to other muscle groups, causing altered facial expression, difficulty chewing, dysphagia, weakened voice, and impaired fine hand movements. Signs of respiratory distress reflect weakness of the diaphragm and other respiratory muscles.

Ophthalmoplegic migraine

Most common in young adults, an ophthalmoplegic migraine produces ocular deviation and diplopia that persist for days after the pain subsides. Associated signs and symptoms include unilateral headache, possibly with ptosis on the same side; temporary hemiplegia; and sensory deficits. Irritability, depression, or slight confusion may also occur.

Orbital blowout fracture

In an orbital blowout fracture, the inferior rectus muscle may become entrapped, resulting in limited extraocular movement and ocular deviation. Typically, the patient’s upward gaze is absent; other directions of gaze may be affected if edema is dramatic. The globe may also be displaced downward and inward. Associated signs and symptoms include pain, diplopia, nausea, periorbital edema, and ecchymosis.

Orbital tumor

Ocular deviation occurs as the tumor gradually enlarges. Associated findings include proptosis, diplopia and, possibly, blurred vision. The eyelid may also appear edematous.

Stroke

Stroke is a life-threatening disorder that may cause ocular deviation, depending on the site and extent of the stroke. Accompanying features of a stroke are also variable and include altered LOC, contralateral hemiplegia and sensory loss, dysarthria, dysphagia, homonymous hemianopsia, blurred vision, and diplopia. In addition, the patient may develop urine retention or incontinence or both, constipation, behavioral changes, headache, vomiting, and seizures.

Thyrotoxicosis

Thyrotoxicosis may produce exophthalmos — protruding eyes — which, in turn, causes limited extraocular movement and ocular deviation. Usually, the patient’s upward gaze weakens first, followed by diplopia. Other features are lid retraction, a wide-eyed staring gaze, excessive tearing, edematous eyelids and, sometimes, inability to close the eyes. Cardinal features of thyrotoxicosis include tachycardia, palpitations, weight loss despite increased appetite, diarrhea, tremors, an enlarged thyroid, dyspnea, nervousness, diaphoresis, heat intolerance, and an atrial or ventricular gallop.

Special considerations

Continue to monitor the patient’s vital signs and neurologic status if you suspect an acute neurologic disorder. Take seizure precautions, if necessary. Also, prepare the patient for diagnostic tests, such as blood studies, orbital and skull X-rays, and computed tomography scan.

Pediatric pointers

In children, the most common cause of ocular deviation is nonparalytic strabismus. Normally, children achieve binocular vision by age 3 to 4 months. Although severe strabismus is readily apparent, mild strabismus must be confirmed by tests for misalignment, such as the corneal light reflex test and the cover test. Testing is crucial — early corrective measures help preserve binocular vision and cosmetic appearance. Also, mild strabismus may indicate retinoblastoma, a tumor that may produce no symptoms before age 2 except for a characteristic whitish reflex in the pupil.

Patient counseling

Explain the disorder and its treatment to the patient and his family. Teach them to recognize and report changes in LOC. Discuss ways to maintain a safe environment at home and to reduce environmental stress.

Pictures

Book Source Details

• Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
• Author(s): Springhouse
• Year of Publication: 2007
• Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: Signs & Symptoms: A 2-in-1 Reference for Nurses Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-58255-318-1

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