Fig. 7.3  Spasm of near reflex. Twelve-year-old boy had undergone small left medial rectus muscle resection for presumed convergence insufficiency. Four months later, he was noted to have episodic, pronounced spasm of

near reflex (large esotropia, miosis, induced myopia with blurred vision) associated with severe spasms involving eyelids and facial musculature (a). In between spasms, only small esotropia was variably present (b)

Neurologic Exotropia

The differential diagnosis of constant exotropia includes cortical visual insufficiency, craniofacial synostosis, and congenital fibrosis syndrome. Isolated infantile exotropia is a rare but well-recognized nonneurologic condition in which a large-angle exotropia is associated with the same constellation of visuovestibular disorders that accompany infantile esotropia. Some early-onset cases of intermittent exotropia also fall into this group.384 Some cases of infantile exotropia are hereditary, showing an autosomal dominant inheritance pattern.119 Nevertheless, the clinician must maintain a high index of suspicion for neurologic disease in the child with infantile exotropia.

In our experience, constant exotropia is most commonly seen in the setting of cortical visual insufficiency secondary to hypoxic-ischemic encephalopathy.118 Associated signs include horizontal conjugate gaze deviation with little or no nystagmus and mild or sectoral pallor of the optic discs.118 Because children with congenital homonymous hemianopia may develop a constant exotropia that serves to expand the existing visual field, confrontation visual fields should be checked in this setting. Signs of craniofacial disease are usually apparent on initial examination. As detailed below, fixed downgaze, associated ptosis, sparing of pupillary function, and similar findings in other family members provide clinical clues to the diagnosis of congenital fibrosis syndrome.

Convergence Insufficiency

Convergence insufficiency is a common condition characterized by:(1) diplopia or blurring at near, (2) decreased convergence amplitudes, and (3) a recessed near point of accommodation.401 It seems to afflict intelligent patients and is considered to be the one form of strabismus that is treatable with eye exercises. Convergence training has been

shown to improve proximal and tonic convergence, but not accommodative or fusional convergence.33

Convergence insufficiency is most commonly a primary condition presenting in young adults. In this setting, it is presumably caused by an inborn deficiency or acquired imbalance of vergence eye movements that has yet to be identified.33 In this setting, patients may present with sleeping on reading or near work, tearing, heavy lids, uncomfortable eyes, asthenopic symptoms, double vision, or blepharitis (from frequent rubbing of the eyes). These patients perform their near work optimally immediately after awakening.

Convergence insufficiency is also a prominent accompaniment of neurologic disease, having been reported in association with head trauma,19,130,181,450,452,483,719 neurodegenerative disorders,75,125,631 infarction,390,593 thyroid ophthalmopathy,126 myasthenia gravis, toxic agents, medications,125,738 inflammation,125,620 decompression sickness,493 whiplash injuries,134 and attention-deficit hyperactivity disorder (ADHD).310 In the last mentioned condition, it is not always clear whether convergence insufficiency is the cause or effect, whether they are comorbid conditions, or whether medications used to treat the ADHD may contribute to the convergence insufficiency.

Some believe that accommodative insufficiency is the primary source of symptoms in children diagnosed with convergence insufficiency,520 although this issue continues to be debated.680 Therefore, accommodative amplitudes and dynamic retinoscopy should be examined to rule out an underlying or associated accommodative paresis.653 It is also important to check for undetected ocular torsion, which can secondarily impair convergence. The potential pharmacological role of any medications in impairing accommodation should always be considered.130

Convergence insufficiency should not be confused with convergence paralysis, another neurologic disorder in which there is a constant exotropia at near. Although convergence exercises are the mainstay of treatment for convergence insufficiency,613 treatment with base in prisms has also been