Prompt recognition and treatment of accommodative esotropia are critical for successful outcomes. The mainstay of treatment is spectacles, but other modalities for correction of refractive error, including contact lenses and refractive surgery, may be employed in the chronic phase. Some patients may also require strabismus surgery.
The main goals of the ophthalmologist, when treating a child with accommodative esotropia, are to maintain normal visual acuity in both eyes, restore normal ocular alignment, and maintain good binocular function. Clearly, achieving these goals is easiest during the early, intermittent stage of the deviation. However, children often present in the office beyond this stage and have developed amblyopia. In these patients, patching or atropine therapy are required to improve the visual acuity. Restoring visual acuity in patients with accommodative esotropia and amblyopia has been achieved in approximately 40% to 80% of cases. In addition, after correction of the full cycloplegic refraction, normal ocular alignment has been achieved in approximately 50% of cases, with reports ranging from 40% to 100%. Children who do not receive hyperopic correction for several months may develop a nonaccommodative component to their esotropia, resulting in residual esotropia despite full correction of their hyperopia (partially accommodative esotropia).
Spectacles: the Mainstay of Treatment
Patients with normal AC/A ratio should receive single-vision spectacles initially. Patients with high AC/A ratio on the first visit should usually receive flat-top-style bifocal (D-segment) spectacles from the beginning. Glasses involve a large investment of time and money for the parents, and the ophthalmologist’s guidance to parents in helping them understand potential problems in initiating glasses is very helpful. An information sheet on how to select attractive comfortable glasses for children is often appreciated if there is no expert optician to whom the family can be directed (also see Tables 3 and 4). It is helpful to explain up front that the glasses are for alignment and not for vision and that they require the child to relax the focusing muscles of the eyes, which can take time. Persistence and encouragement are the key ingredients for success. Reassurance and encouragement by office staff are often needed, in direct proportion to how soon the parental phone calls start. Sometimes it is easiest to have the child wear the glasses for near activities and increase use over time. If after 2 weeks the child is not wearing the glasses well, the use of cycloplegic drops at home, such as atropine 1% in each eye once a day for 1 week, can facilitate proper wear.
Several weeks to months after initiation of spectacle wear, children should be reexamined to reassess the angle of esotropia. If there is residual esotropia, the child should undergo repeat cycloplegic refraction. If additional latent hyperopia is identified, new hyperopic spectacles should be prescribed. If the child has a residual deviation only at near, bifocals are added. Children who achieve successful ocular alignment with spectacles alone typically remain in their full cycloplegic refraction until 6 to 7 years of age. Several studies have indicated that, unlike typical children who become less hyperopic with advancing age, children with accommodative esotropia generally develop increasing amounts of hyperopia until about age 7 followed by a gradual decrease thereafter. Periodic follow-up, approximately every 6 to 12 months, is necessary to manage the spectacles and monitor for amblyopia.
Use of Bifocals
Children who are orthotropic at distance with correction, but esotropic with near fixation, are considered for a bifocal (high AC/A ratio). Also, children who clearly have an increased AC/A ratio on first exam are generally placed in bifocals initially. The initial amount of bifocal correction is determined by the minimum add required to obtain orthotropia at near fixation, which is usually +2.50 D to +3.00 D. Typically, a D segment or executive-type bifocal is used. The add should be placed high enough to be engaged when the child performs near activities. In younger children, this level often bisects the pupil but can be lowered with advancing age in the child who uses the adds appropriately.
Progressive, or no-line, bifocals are cosmetically more appealing and often desired by the parents; however, the power required for good alignment is typically located too low in the smaller pediatric spectacles. As a result, this type of bifocal is often reserved for older children and teenagers who will seek out the area of greater plus power and be successful with them. It is important to explain the reason for a bifocal and inform the parents that children, unlike middle-aged adults, adapt very well, even when playing soccer. Parents will often see a chin-up position when something is held in front of the child, which indicates proper use of the bifocal.
Figure 1a shows a 5-year-old with a comitant esotropia that was greater at near than distance fixation and consistent with a diagnosis of refractive accommodative esotropia with a high AC/A ratio. His cycloplegic refraction was +3.00 D sphere bilaterally. He was placed in a bifocal spectacle with +3.00 D adds. His esotropia with distance fixation resolved when looking through the top segment of his spectacles (Figure 1b). However, because of the high AC/A ratio, he developed esotropia when looking over the bifocal with near fixation (Figure 1c). The esotropia at near resolves when he looks through the bifocal segment for near fixation (Figure 1d).
Adjustments for Hyperopia
It has been shown that the hyperopia in accommodative esotropia begins to plateau at about age 6 to 7, and starts to regress slowly. If the child is overplussed because of growth, the parent may notice that the child begins to look over the top of the frames. Control over eye position often improves at this age as well, allowing the power of the correction to be reduced. This can be determined by holding minus lenses over the spectacles in the office and measuring the ocular alignment. The hyperopia is then reduced by the amount tolerated without inducing manifest esotropia or a phoria of greater than about 6 PD. Often the reduction is in steps of 1/2 to 1 D. This process is repeated at follow-up evaluations, typically every 6 to 12 months, until the spectacles are successfully weaned or reduced to the minimum required to prevent esotropia. Bifocals can be weaned in a similar manner, although the jump from available +1.00 adds to nothing may take longer. Eliminating the bifocal segment is a high priority because the older child can then switch to contact lenses, which are becoming more popular in that age group.
Approximately 80% of patients with accommodative esotropia will only require correction of hyperopia with spectacles if they are seen early before amblyopia develops. The development of a nonaccommodative component to the angle of esotropia is often related to a delay in diagnosis, undercorrecting the hyperopia, a high AC/A ratio, earlier onset of the esotropia, inferior oblique overaction, amblyopia, and poor compliance with spectacle wear, increasing the chance of needing surgery to as much as 50%.
Traditionally, surgery consists of medial rectus muscle recessions based on the residual esotropia at distance fixation while wearing the full cycloplegic refraction. Some advocate using the near angle measurement, and others suggest an average of the near measurements with and without spectacles. These other approaches derive from a higher frequency of postoperative undercorrection with the more traditional approach of operating based on the distance deviation.
Children with high AC/A ratios and residual esotropia even with the bifocals may also require surgical correction. The surgical approach in these cases typically involves medial rectus muscle recessions, but often with some modification. Some advocate operating for the angle of deviation measured at near in patients with a high AC/A ratio. Others recommend placement of posterior fixation sutures (Faden operation) on the recessed medial rectus muscles to weaken them in their field of action and not disrupt their action in the primary position. However, this surgery is technically more difficult and has had a greater incidence of scleral perforation than simple recessions. Kushner found that augmented bilateral medial rectus muscle recessions, based on the amount that the near deviation exceeds the distance deviation with spectacles, was more successful than standard bilateral medial rectus muscle recessions with posterior fixation (Faden operation). Kushner recommended augmenting standard medial rectus muscle recessions by 1 mm for a difference of 10 PD, 1.5 mm for 15 PD, and 2 mm for 20 PD or more, to a maximum recession of 6.5 mm. For the teenager who still requires bifocals, medial rectus recessions for the near deviation with the full cycloplegic refraction in place can be very successful in eliminating the need for bifocals.
Prism adaptation has also been used as a preoperative tool in patients with acquired esotropia. The Prism Adaptation Study of 1990 showed that preoperative prism adaptation improved the chance of good postoperative surgical alignment. Prism adaptation required the use of Fresnel membrane prisms applied to glasses and additional office visits for adjustment and replacement, depending on the angle of strabismus, prior to strabismus surgery. Patients who were identified as “responders” (stable esotropia of 8 PD or less through the prisms and fusion of the Worth four-dot test at near) had an 83% success rate with strabismus surgery versus 72% in those without prism adaptation. Prism adaptation is not widely employed likely due to significantly increased time and cost, a substantial minority (one-third) who do not respond to adaptation, and the minimally increased surgical success rate.