All patients with exodeviations should be monitored as some will require treatment. Opinions vary widely regarding the timing of surgery and the use of nonsurgical treatments. Patients who have well-controlled, asymptomatic intermittent exotropia and good binocular fusion can be observed. Untreated strabismus often results in poor self-esteem in adults and children. Adults with strabismus report a wide range of difficulties with social interactions, which improve significantly after surgery.
Correction of refractive errors
Corrective lenses should be prescribed for significant refractive errors. Correction of even mild myopia may improve control of the exodeviation. Mild-to-moderate degrees of hyperopia are not routinely corrected in children with intermittent exotropia because refractive correction may worsen the deviation. Children with marked hyperopia (>+4.00 D) may be unable to sustain accommodation, which results in a blurred retinal image and manifest exotropia. In these patients, correction of refractive errors with glasses or contacts may improve retinal image clarity and help control the exodeviation.
In some cases, overcorrection of myopia by 2.00–4.00 D can stimulate accommodative convergence to help control the exodeviation. It can be effective as a temporizing measure to promote fusion and delay surgery in children with an immature visual system. This therapy may cause asthenopia in school-aged children, however. For patients whose initial overcorrection results in control, the prescription can be gradually tapered and surgery may be avoided.
Occlusion therapy (patching) for amblyopia may improve exotropic deviations. For patients without amblyopia, part-time patching of the dominant (nondeviating) eye or alternate patching (alternating which eye is patched each day) in the absence of a strong ocular preference can improve control of small- to moderate-sized deviations, particularly in young children. The improvement is often temporary, however, and many patients eventually require surgery.
Although they can be used to promote fusion in intermittent exotropia, base-in prisms are seldom chosen for long-term management because they can cause a reduction in fusional vergence amplitudes.
Factors influencing the decision to proceed with surgery include strabismus that is frequently manifest, poorly controlled, worsening (especially at near), symptomatic; poor self-image; and difficulty with personal or professional relationships. Strabismus surgery in adults is reconstructive, not cosmetic, and may alleviate anxiety and depression in some patients.
Surgical treatment of exotropia typically consists of bilateral lateral rectus muscle recession or unilateral lateral rectus muscle recession combined with medial rectus muscle resection. Large (>50Δ) deviations may require surgery on 3 or 4 muscles; for small deviations, single-muscle recession is sometimes performed. The optimal age for surgery and the choice of procedure are debatable. Caution is advised when surgery is considered for patients with true divergence excess exotropia, as they are at risk for postoperative diplopia and esotropia at near.
Adams GG, McBain H, MacKenzie K, Hancox J, Ezra DG, Newman SP. Is strabismus the only problem? Psychological issues surrounding strabismus surgery. J AAPOS. 2016;20(5):383–386.
Joyce KE, Beyer F, Thomson RG, Clarke MP. A systematic review of the effectiveness of treatments in altering the natural history of intermittent exotropia. Br J Ophthalmol. 2015;99(4):440–450.
A small-angle esotropia in the immediate postoperative period tends to resolve and is desirable because of its association with a reduced risk of recurrent exotropia. Patients may experience diplopia while esotropic, and they should be advised of this possibility preoperatively. An esodeviation that persists beyond 3–4 weeks or that develops 1–2 months after surgery (postsurgical esotropia) may need further treatment, such as hyperopic correction, base-out prisms, patching to prevent amblyopia, or additional surgery. Bifocal glasses can be used for a high AC/A ratio and should be discussed preoperatively with patients who have true divergence excess. Unless deficient ductions suggest a slipped or “lost” muscle, a delay of a few months is recommended before reoperation for postsurgical esotropia, as spontaneous improvement may occur.
Because of the possibility of persistent consecutive esodeviations, some ophthalmologists prefer to delay surgery in young children who have good preoperative visual acuity and stereopsis. Others, however, consider surgical delay a risk factor for recurrence of strabismus. Long-term follow-up studies of the effectiveness of surgical treatment of intermittent exotropia show high recurrence rates. Patients may require multiple surgeries to maintain ocular alignment long term.
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.