Constant exotropia is encountered most often in older patients with sensory exotropia or in patients with a history of long-standing intermittent exotropia, which has decompensated. Constant exotropia also occurs in persons with infantile or consecutive exotropia. A patient with an exotropia that is constant can have basic, pseudodivergence excess, or true divergence excess exotropia—the same forms seen in intermittent exotropia.
Surgical treatment is the same as that for intermittent exotropia, discussed earlier in the chapter.
Some patients with constant exotropia have an enlarged field of peripheral vision because they have large areas of nonoverlapping visual fields. These patients may notice a field constriction when the eyes are straightened.
Infantile exotropia is much less common than infantile esotropia. Constant infantile exotropia is apparent before age 6 months as a large-angle deviation (Fig 9-1). The risk of amblyopia is higher in constant exotropia than in intermittent exotropia. Although infants with constant exotropia may be otherwise healthy, the risk of associated neurologic impairment or craniofacial disorders is increased in these patients. A careful developmental history is thus important, and referral for neurologic assessment should be considered if there are indications of developmental delay. Patients with constant infantile exotropia are operated on early in life, and outcomes are similar to those for infantile esotropia (see Chapter 8). Early surgery can lead to monofixation with gross binocular vision, but restoration of normal binocular function is rare. Dissociated vertical deviations and overelevation in adduction may develop (see Chapter 11).
Figure 9-1 Infantile exotropia. A, This 10-month-old infant with infantile exotropia also shows developmental delay. B, Krimsky test. Two base-in prisms are used to measure the large exotropia.
(Reproduced from Wilson ME. Exotropia. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 1995, module 11.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.