Diplopia

The Problem

“I see two of things.”

Common Causes

Physiological diplopia

Breakdown of phoria

Cranial nerve palsy

Third nerve palsy

Fourth nerve palsy

Sixth nerve palsy

Other Causes

Decompensated childhood strabismus Duane syndrome

Myasthenia gravis (discussed in ptosis chapter)

KEY FINDINGS

History

Physiological diplopia

Usually noticed about ages 5 to 6 years Most common in bright, observant children Not bothered by symptoms

Breakdown of phoria

Often no known history of strabismus

Develop strabismus and diplopia during severe illness Resolves after recovery of illness

Cranial nerve palsies Third nerve palsy

Horizontal and vertical diplopia Ptosis

Unequal pupils (anisocoria) Fourth nerve palsy

Usually gradually worsening vertical diplopia Head tilt

Sixth nerve palsy Horizontal diplopia Recent viral illness

Idiopathic intracranial hypertension Headache

Brief episodes of vision loss (transient visual obscurations)

Recent medication change Corticosteroids, isotretinoic acid, others

Examination

Physiological diplopia

Normal ophthalmic examination Normal physical examination

Breakdown of phoria

Variable esotropia or exotropia

No limitation of extraocular movements Cranial nerve palsies

Fourth nerve palsy Usually head tilt

Eyes straight when head tilted to unaffected side

Vertical misalignment when tilted to affected side

Sixth nerve palsy Esotropia

Inability to move affected eye outward Idiopathic intracranial hypertension

Obesity Papilledema

Third nerve palsy Eye out and down

Ptosis on affected side

Anisocoria (affected pupil larger in acquired third nerve palsy)

Possible other neurological signs

74 ■ Section 2: Symptoms

WHAT SHOULD YOU DO?

Most children with strabismus do not experience diplopia. This symptom warrants referral to an ophthalmologist. If the examination suggests a cranial nerve palsy, or if other neurological symptoms are present, the child should be seen promptly.

What Shouldn’t Be Missed

Acute cranial nerve palsies may be due to idiopathic intracranial hypertension or other intracranial diseases. Prompt evaluation and treatment may improve the prognosis for both vision and the underlying disorder.

COMMON CAUSES

1.Physiological diplopia. This is a normal phenomenon that is most commonly noted by bright and observant children around ages 5 to 6 years. The eyes normally focus on objects in a single plane, and these are seen as single images. Objects in front of or behind the object of attention appear to be double, but most people do not notice this. The diplopia can be demonstrated by holding one finger up at arm’s distance in front of your face, with another object (e.g., something on the wall) in the background in line with your finger. If you focus on your finger but pay attention to the object in the background, the background object will appear double. Conversely, if you focus on the background object but pay attention to your finger, the finger will appear double (Figure 11–1). Most of the time these double images are ignored, but children may become aware of them and report them to their parents.

2.Breakdown of a phoria. Many normal individuals have a phoria. A phoria is a tendency for the eyes to become misaligned when one eye is covered. The eyes are straight during normal viewing conditions with both eyes open. With a phoria, when one is covered it drifts off center (either inward or outward). The eye returns to its normal position when the eye is uncovered (Figure 11–2). In some patients, usually in association with severe illness or trauma, the ability to control the phoria is temporarily lost, and they develop manifest strabismus (esotropia or exotropia) and diplopia. This usually resolves in conjunction with recovery from the underlying problem.

3.Fourth nerve palsy. This is most often congenital and not associated with other neurological problems.

FIGURE 11–1 ■ Physiological diplopia. (Top) This can be demonstrated by holding two objects in line with each other in front of the eyes. (Middle) If the eyes focus on the near object, the far object will appear double. (Bottom) If the eyes focus on the far object, the near object will appear double (bottom figure).

FIGURE 11–2 ■ Left esophoria. (Top) The eyes are normally straight. (Middle) If a cover is placed in front of the left eye, the eye moves inward behind the cover. (Bottom) When the cover is removed, the left eye returns to its normal position.

4.Third nerve palsy. Acquired third nerve palsy may result from many different neurological problems.

5.Sixth nerve palsy. Most common causes are transient sixth nerve palsy of childhood (often associated with preceding viral illness) and increased intracranial pressure.

APPROACH TO THE PATIENT

Strabismus in childhood is most commonly due to the disorders discussed in Chapters 7 and 8. In these forms of strabismus it is unusual for children to complain of diplopia because the child’s visual system typically suppresses (ignores) the image from the misaligned eye. When a child complains of diplopia, prompt investigation may be warranted if there is evidence of an acute cranial nerve palsy.

History

The primary concern in a child who reports diplopia is whether a cranial nerve palsy is present. Cranial nerve palsies may result from trauma, which is usually severe. In this case a history of injury would be easily identified. In the absence of trauma, other neurological signs or symptoms, such as headache, lethargy, nausea, and vomiting, should raise concern. A complete neurological review of systems should be obtained in these patients.

Cranial nerve palsies need to be differentiated from a breakdown of a phoria, which may also occur in association with a severe illnesses or trauma. Both may cause diplopia, and they are differentiated from one another by the examination and history (Table 11–1).

Some cranial nerve palsies in children are benign, particularly congenital fourth nerve palsies. These produce a vertical strabismus that is worse when the head is tilted to the side of the palsy. The patients typically develop a compensatory head tilt to the opposite side to minimize the strabismus. In some families, this occurs so frequently that the family no longer notices it. Evaluation of old photographs may show that a head tilt has been present since early childhood. These children often do not complain of diplopia when they are young, but when they are older they may describe vertical diplopia when their head is tilted to side of the palsy or when they look to the side.

Children may develop transient sixth nerve palsies in the absence of other neurological problems. If the children are old enough to verbalize symptoms, they usually complain of horizontal diplopia. These patients often have a history of a viral illness in the few weeks before the onset of the palsy.

CHAPTER 11 Diplopia ■ 75

Table 11–1.

Differentiating Breakdown of a Phoria From a

Cranial Nerve Palsy

Associated illness

■Phoria: Symptoms occur during acute illness or after trauma

■Cranial nerve palsy: May have neurological symptoms, often normal

History

■Phoria: Usually no history of strabismus

■Cranial nerve palsy

Sixth nerve palsy: often after viral illness

Fourth nerve palsy: often long history of head tilt

Examination

■ Phoria

Esotropia or exotropia

No limitation of extraocular movements Examination usually normal after illness resolves

■Cranial nerve palsy Fourth nerve

–Head tilt to side opposite palsy

–Vertical strabismus when head tilted to side of palsy

Third nerve

–Eye out and down

–Ptosis

–Pupil smaller on affected side

Sixth nerve

–Esotropia

–Limited outward movement of eye

–If increased intracranial pressure: papilledema

Children with physiological diplopia usually describe seeing double at approximately 5 to 6 years of age. They are usually not bothered by this phenomenon, and often it is first brought to attention during casual conversation with their parents. These children are otherwise healthy, have no neurological symptoms, and are often described as bright and observant.

Examination

The evaluation of a child with diplopia should include a complete neurological examination. Direct ophthalmoscopy should be performed to look for papilledema. Children with diplopia due to breakdown of a phoria usually have visible esotropia or exotropia during the illness that precipitates the diplopia. Their extraocular movements are otherwise normal, with no limitation, which differentiates this problem from a cranial nerve palsy. The ocular findings that occur in third, fourth, and sixth cranial nerve palsies are described in Chapter 10. Children with physiological diplopia have normal examinations.

Cranial nerve palsy

PLAN

If an acute cranial nerve palsy is suspected, children should be referred promptly for further studies. These usually include central nervous system imaging and ophthalmology and neurology consultations. If a congenital fourth nerve palsy is suspected (based on a long-standing head tilt), referral to a pediatric ophthalmologist is recommended. Most of these children do not require imaging. If physiological diplopia is suspected, referral to a pediatric ophthalmologist is indicated to verify the diagnosis (Figure 11–3).

CHAPTER 11 Diplopia ■ 77

WHAT SHOULDN’T BE MISSED

Children with the new onset of diplopia may have cranial nerve palsies, which may be due to central nervous system lesions.

When to Refer

■ Urgent referral if other abnormalities

Signs of cranial nerve palsy Signs of orbital abnormality

■ Otherwise regular referral