Infantile Esotropia Treatment & Management

Smaller angles of deviation may be addressed with prism lenses with or without occlusion therapy, depending on the existence of amblyopia. Perform a good refraction with full cycloplegia on all esotropic infants. A common cycloplegic combination is 2.5% phenylephrine and 1% cyclopentolate. It is necessary to occlude one eye at a time during retinoscopy to make sure that the examiner maintains accurate alignment with the visual axis. The average cycloplegic refraction of a child with infantile esotropia with no other developmental or systemic problem is a mild hyperopic spherical equivalent with mild astigmatism, which is relatively stable in the first decade of life.

Corrective lenses generally are prescribed with hyperopia greater than +2.50 diopter (D) and/or when anisometropia exceeds 1.50 D. In addition, any cylinder greater than or equal to +0.50 D should be given spectacles. On the other hand, myopia above -4.00 D warrants corrective lenses. Correcting moderate-to-severe hyperopia is performed to eliminate a significant refractive esotropia superimposing upon a preexistent infantile esotropia. Correction of myopia is performed for 2 reasons. First, it is to clear the images seen by the infant so that it increases the chances of accurate fixation and consequently generates more accurate strabismus measurements. Second, minus lenses may alter the accommodative demand and the infant's strabismus angle, particularly when fixating near targets.

If amblyopia is discovered, appropriate occlusion therapy is instituted at once. The rule of thumb observed is 1-2 weeks of high percentage (eg, 90% of waking hours) occlusion of the nonamblyopic eye per year of life, especially if a strong fixation preference for one eye is detected. The infant is reexamined after a few weeks to determine response to therapy and to ensure that occlusion-induced amblyopia has not developed in the occluded dominant eye. If close, frequent follow-up visits will not be possible, then lower percentage occlusion therapy can be initiated. The endpoint of occlusion therapy is to achieve a pattern of freely alternating equal vision.

Botulinum toxin (BOTOX®) injection into the medial rectus has recently been explored as an alternative therapy to surgery. Several studies have investigated the merits of such a procedure with contrasting results. In the work using concurrent bilateral medial rectus BOTOX® injections, McNeer et al noted a decrease in the esotropic angle in 27 patients with infantile esotropia younger than age 12 months, from 43 to 1±2 PD, and in patients younger than age 24 months, from 31±12 to 2±3 delta.^[8] Long-term studies up to 95 months postinjection follow-up were conducted by the same authors showing not only a significant reduction in esotropic angle but also successful binocular alignment (±10 PD) in 89% of the patients.^[9]

In a separate study by Scott et al, it was noted that 65% of the study patients with infantile esotropia achieved correction of 10 PD or less following BOTOX® injection, with smaller deviations (10-20 PD) more frequently corrected than larger deviations (20-110 PD).^[10] No globe perforation, amblyopia, or visual loss was reported as a result of the injections. Tejedor and Rodriguez claimed that BOTOX® injection was a rapid and less invasive alternative to reoperation in children who had been treated unsuccessfully with surgery to correct infantile esotropia.^[11]

However, not all studies were convincing of the efficacy of BOTOX® injections. Ing contended that alignment by BOTOX® injections appeared to be less effective in establishing evidence for binocularity than incisional surgery in the treatment of congenital esotropia.^[12] On the other hand, while Biglan et al agreed that BOTOX® injections may be useful in the management of patients with recent surgical overcorrections, it was not as successful as traditional strabismus surgery for the treatment of infantile esotropia.^[13] In a review of randomized controlled trials on the use of botulinum toxin for strabismus, Rowe and Noonan noted that there was no significant difference between the former and surgery for patients with infantile esotropia.^[14]

Infantile esotropia is characterized by large angles of deviation (>40 PD) and customarily is corrected surgically. Tychsen stressed that when the surgeon has documented that the infant has a constant esotropia exceeding 12 PD, surgical realignment should be performed.^[4] The surgeon must obtain 2 reasonably high-quality reproducible strabismic measurements, which agree to a range of 5-10 PD, before proceeding with the operation.

Over the years, a number of surgical techniques have been developed, but most of them involve bilateral medial rectus recession, wherein the insertion of the muscles into the globe is transferred posteriorly consequently weakening their adducting action. An alternative is a unilateral medial rectus recession - lateral rectus resection (shortening of the muscle leading to increased abducting power). A randomized comparison of the effectivity of the two procedures noted no significant difference.^[15] Variations in technique depend on the total number of muscles initially involved (eg, 2, 3, or 4, wherein lateral rectus resection or shortening also is performed) and the amount of medial rectus recession carried out.

Adjustment of the amount of correction is just as important. Chang et al described a one-stage intraoperative adjustment of strabismus surgery with adjustable sutures to be a simple, well-tolerated, and effective procedure.^[16]

A controversial issue is the timing of surgery. While the beneficial effect of accurate alignment by age 2 years has been well established and widely practiced, the earliest age at which surgery should be performed has yet to be defined convincingly. Whether or not to undertake alignment procedures before age 1 year has triggered much debate and vigorous investigations. Studies have shown that performing strabismus surgery at or before 10-11 months of age enhances sensory and ocular motor development and that strabismus surgery does not need to be delayed while waiting for the angle of deviation to be stabilized.

Zak and Morin claimed that corrective surgery from age 5-24 months produced successful alignment of the eyes to within 10 PD of orthophoria with a higher prevalence of fusion and stereopsis and a lower prevalence of dissociated vertical deviation (DVD).^[17] Furthermore, inferior oblique overaction and amblyopia were less frequent when the initial operation had been performed before age 12 months.

Shirabe et al concurred with such findings but added that it was necessary to confirm a stable angle of deviation with accurate preoperative evaluation and to maintain good postoperative eye alignment throughout the follow-up period to achieve and maintain the binocular visual function resulting from early corrective surgery.^[18] Birch et al explained that better stereopsis is achieved with early surgical alignment because the duration of misalignment is shortened and not because alignment is achieved during an early critical period of visual maturation.^[19]

The long-term outcome of early surgical correction of infantile esotropes (mean postoperative follow-up period is 14.7±3.7 y) showed that an eventual loss of binocular alignment occurred in some patients but at a much later age, with reduced chances of developing oblique muscle overactions. Children who undergo surgical alignment at age 6 months have a higher prevalence of coarse stereopsis than those who are corrected surgically at age 7-15 months.

Moreover, in a separate study of infantile esotropes who underwent surgical alignment before age 1 year, 3 distinct groups were defined, as follows: (1) those who remained stable following their initial early alignment, (2) those who were well aligned and remained stable for prolonged periods of time and then decompensated, and (3) those who were unstable throughout the observation period.

These findings illustrate the instability of the conditions of patients with infantile esotropia. While apparent benefits with regard to improved binocularity and visual acuity had been demonstrated with early surgical correction of infantile esotropia, a need exists for repeated thorough observations in the first decade of the patient's life.

Over the years, new surgical modalities have been proposed to address childhood esotropia and concomitant ocular problems in children.

• Lueder and Norman performed strabismus surgery as an alternative to bifocal glasses in treating accommodative esotropia with favorable results.^[20] They concluded that strabismus surgery may eliminate the need for bifocal glasses in patients with accommodative esotropia with a high accommodative convergence/accommodation (AC/A) ratio.
• Ticho et al noted that simultaneous extraocular muscle and lens surgery is an option for patients with strabismus and lens abnormalities.^[21] The authors recommended using standard strabismus surgical amounts. Very few postoperative complications were reported.
• Godts et al reported that preoperative intermittent or manifest strabismus was not a contraindication for refractive surgery, provided some specific recommendations are taken into account, such as an adequate preoperative orthoptic examination and a goal of emmetropia for both eyes.^[22]

Consultation with a pediatric ophthalmologist may be indicated.

Upon fully recovering from general anesthesia, the child is allowed to roam and play freely. Parents can bathe and wash the patient's face without undue concern, especially if a fornix approach was used for the incision. Occlusion therapy is discontinued during the first postoperative week. However, spectacles should be worn during this time.