Children with strabismus should be referred to an ophthalmologist. If an acute cranial nerve palsy is suspected, referral to a pediatric neurologist and brain imaging may be indicated.

What Shouldn’t Be Missed

Third, fourth, and sixth cranial nerve palsies may initially present with strabismus. Although some causes of these palsies are benign or self-limited, they may be due to central nervous system infections, tumors, or other serious diseases.

• 1. Accommodative esotropia. Accommodative esotropia is a form of eye crossing due to farsightedness. The majority of children in the first several years of life are farsighted. Few young children need to wear glasses, however, because the lens is able to change its shape to focus (accommodation), as if the children have a built-in pair of glasses. When children are more farsighted than normal, the effort to focus is greater, and this effort may induce esotropia. The esotropia usually resolves when the farsightedness is corrected with spectacles. Bifocal glasses are sometimes used if the eye crossing is worse when viewing near objects (Figure 10–1A and B).
  
• 2. Acute comitant esotropia. Esotropia that is not due to farsightedness may occasionally develop rapidly in children after infancy. These children often have a family history of strabismus, and they do not experience diplopia. It is felt that many of these children have had a strabismic tendency that was never noticed, and that at some point they lose the ability to control this and develop manifest strabismus. These children are usually otherwise healthy, but the acute onset may warrant evaluation to rule out other abnormalities.
  
• 3. Exotropia. Exotropia usually presents in older children, but may develop in infancy. In most patients it is intermittent, and the vision is usually normal in both eyes. It is more noticeable when children are tired, ill, or daydreaming, and it is worse when viewing distant objects (Figure 10–2).
  
• Older children with exotropia are usually otherwise healthy. It is unusual for exotropia to present before 1 year of age, and infantile exotropia may be associated with developmental delay. If the exotropia is constant at any age, there may be an underlying ocular disorder causing decreased vision (i.e., the exotropia is a secondary effect of the decreased vision).
  
• 4. Recurrent strabismus following infantile esotropia. Infantile esotropia usually appears by 3 to 4 months of age. It is treated by surgically weakening or strengthening the horizontal extraocular muscles. Patients with any form of strabismus may require more than 1 surgery to attain adequate ocular alignment, and the need for additional surgeries is more common in children with infantile esotropia. Recurrent strabismus may manifest as eye crossing (recurrent esotropia), outward drifting (consecutive exotropia), or vertical eye misalignment (dissociated vertical deviation or inferior oblique muscle overaction).
  
• 5. Duane syndrome. Duane syndrome results from a congenital miswiring of the cranial nerves that control the extraocular muscles. In the most common form, the nerve that innervates the lateral rectus muscle gets crossed with the nerve that innervates the medial rectus muscle. When the patient attempts to look to the side of the affected eye, there is no innervation to the lateral rectus muscle. The opposite eye moves normally (toward the nose), but the affected eye does not move out. Therefore, the patient appears esotropic. When the patient attempts to look toward the side of the normal eye, both the medial and lateral rectus muscles in the affected eye contract and the eye is pulled posteriorly (globe retraction), which narrows the space between the eyelids and may give the appearance of ptosis or the affected eye appearing smaller than normal (Figure 10–3).
  
• 6. Cranial nerve palsies. Cranial nerves III, IV, and VI innervate the extraocular muscles.
  
  
  
  • a. Cranial nerve III innervates the medial rectus muscle, inferior rectus muscle, inferior oblique muscle, and superior rectus muscle, as well as the eyelid levator muscle, and the iris sphincter muscle. In patients with third cranial nerve palsies the only functioning extraocular muscles are the superior oblique and lateral rectus muscles. Therefore, the affected eye is out and down, and the patient has ptosis and a dilated pupil on the affected side (Figure 10–4). Of the 3 cranial nerve palsies discussed here, third nerve palsies are the most likely to be associated with significant intracranial disorders.
    
  • b. Cranial nerve IV innervates the superior oblique muscle. This muscle moves the eye down when it is turned toward the nose. In fourth nerve palsies the affected eye is elevated. This elevation is worse when the eye is turned toward the nose or when the patient tilts his or her head toward the side of the palsy. Therefore, patients often present with a head tilt to the opposite side, which is adopted to keep the eyes aligned (Figure 10–5A–C). Fourth nerve palsies may result from intracranial pathology, but they are most commonly considered congenital and otherwise benign. They usually are not present in infancy, but become noticeable later in childhood (sometimes not until adulthood).
    
  • c. Cranial nerve VI innervates the lateral rectus muscle. Patients with sixth nerve palsies cannot turn their eyes outward, and they present with esotropia of the affected eye (Figure 10–6). Unlike most other forms of childhood strabismus, patients with sixth nerve palsies often complain of diplopia. Sixth nerve palsies may occur following viral illness, in which case they are usually benign and self-limited, but they may also occur due to increased intracranial pressure.