Characteristics

Accommodative esotropia describes an esotropia caused in whole, or in part, by the use of accommodation to clear vision in the presence of uncorrected hypermetropia. This association is widely attributed to Donders.¹ Accommodative esotropia is one of the most common forms of childhood strabismus accounting for about a third of all strabismus patients in most studies in Europe and North America.²

The typical age of onset ranges from 2 to 5 years old, but may present earlier (“infantile accommodative esotropia”) or, less commonly, at a later age. Caregivers typically report crossing that is intermittent initially and most apparent when the child is fixing on a near object or when fatigued. With time, the crossing occurs more frequently and, without treatment, often becomes constant. Accommodative esotropia may manifest suddenly following a minor illness, trauma, or without any obvious precipitating event.

Classification

The most widely accepted classification of accommodative esotropia includes four distinct types:

Fig. 75.1 A 3-year-old girl presents with a new onset of left esotropia (with strong fixation preference for the right eye). The deviation is 35 PD at near and distance fixation. The cycloplegic refraction is +4.25 OD and +4.50 OS.

Fig. 75.2 The same girl as in Figure 75.1 4 weeks later wearing her full hyperopic correction. She has a small left esotropia with fixation preference for her right eye. Part-time occlusion therapy of the right eye is begun.

The accommodative convergence/accommodation ratio

The accommodative convergence/accommodation ratio (AC/A) plays an important role in the development, treatment, and prognosis in accommodative esotropia. Patients with a high AC/A ratio present earlier, are more likely to require surgery, and to have a poorer prognosis for long-term binocular vision.⁵ There are different ways to calculate the AC/A ratio although in clinical practice this is not necessary. A clinical comparison of distance to near deviation is most commonly used to determine whether or not the AC/A ratio is high. Patients can be further classified based on the degree of near–distance disparity:

To calculate the AC/A ratio, either the gradient or heterophoric method can be used. For the gradient method, measure the deviation at a fixed distance while relaxing accommodation by introducing plus lenses as follows:

where p is the power of the lens used, D0 the deviation without lenses, and D1 the deviation with lenses.

In the heterophoric method, near and distance deviations are compared while taking into account the interpupillary distance (IPD) as follows:

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