Refractive accommodative esotropia
Treatment of refractive accommodative esotropia consists of correction of the full amount of hyperopia, as determined under cycloplegia. If binocular fusion is maintained, the refractive correction can later be decreased to 1.00–2.00 D less than the full cycloplegic refraction. Amblyopia, if present, may respond to spectacle correction alone, but treatment with occlusion or atropine may be necessary if the amblyopia persists after a period of spectacle wear (see Chapter 6).
Parents must understand not only that full-time wear of the glasses is important but also that the refractive correction can only help control the strabismus, not “cure” it. Once full-time wear has begun, the esotropia may increase when the child is not wearing glasses, because the child makes a strong accommodative effort to produce an image that is as clear as the one experienced with refractive correction. Discussing these issues with the parents at the time the prescription is given is helpful.
Strabismus surgery may be required when a patient with presumed refractive accommodative esotropia does not achieve an ocular alignment within the fusion range (up to 8Δ–10Δ) with correction (partially accommodative esotropia). Before proceeding with surgery, the ophthalmologist should recheck the cycloplegic refraction to rule out latent uncorrected hyperopia.
High AC/A ratio accommodative esotropia
A high AC/A ratio can be managed optically or surgically; it can also be observed.
Bifocals. Plus lenses for hyperopia reduce accommodation and therefore accommodative convergence. Bifocal glasses further reduce or eliminate the need to accommodate for near fixation. If bifocals are used, the initial prescription should be for flat-top style bifocals (see the chapter on refraction in BCSC Section 3, Clinical Optics) with the lowest plus power needed (up to +3.00 D) to achieve ocular alignment at near fixation. To increase the likelihood that the child will use the bifocal segment, it should be set high enough that the top of the bifocal segment bisects the pupil. Progressive bifocal lenses have been used successfully in older children who know how to use bifocal glasses. An ideal response to bifocal glasses is restoration of normal binocular function (fusion and stereopsis) at both distance and near fixation. An acceptable response is fusion at distance and less than 10Δ of residual esotropia at near with bifocals (signifying the potential for fusion). While some children improve spontaneously with time, others need to be slowly weaned from bifocal glasses. The process of reducing the bifocal power in 0.50–1.00 D steps can be started at about age 7 or 8 years and should be completed by age 10–12 years. If a child cannot be weaned from bifocals, surgery may be considered.
Surgery. Surgical management of high AC/A ratio accommodative esotropia is controversial. Some ophthalmologists advocate surgery (medial rectus muscle recessions with or without posterior or pulley fixation) to normalize the AC/A ratio, which may allow discontinuation of bifocals. The risk of overcorrection at distance is low (<10%). Some ophthalmologists use prism adaptation, which entails using prisms preoperatively to neutralize a deviation for a certain length of time. The prism neutralization can then be used to predict the outcome of surgery and determine the maximum deviation.
Observation. Many patients show a decrease in the near deviation with time, and binocular vision at both distance and near fixation ultimately develops. Some ophthalmologists observe the near deviation as long as the distance alignment allows for the development of peripheral fusion.
For the long-term management of both refractive and high AC/A ratio accommodative esotropia, it is important to remember that hyperopia usually increases until age 5–7 years before it starts to decrease. Therefore, if the esotropia with correction increases, the cycloplegic refraction should be repeated and the full correction prescribed.
If glasses correct all or nearly all the esotropia and if some degree of sensory binocular cooperation or fusion is present, the clinician may begin to reduce the hyperopic correction to create a small esophoria, which is thought to stimulate fusional divergence. An increase in the fusional divergence, combined with the natural decrease of both the hyperopia and the high AC/A ratio, may enable the patient to eventually maintain straight eyes without bifocals or glasses altogether.
Partially accommodative esotropia
Treatment of partially accommodative esotropia consists of strabismus surgery for the deviation that persists while the patient wears the full hyperopic correction. It is important that the patient and parents understand before surgery that its purpose is to produce straight eyes with spectacle wear—not to enable the child to discontinue wearing glasses altogether. In older patients, refractive surgery may be considered to both reduce the hyperopic refractive error and improve the ocular alignment.
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.