Accommodative esotropia is a common form of “crossed eyes” or strabismus, where one or both eyes turn inward toward the nose. This condition is linked to the eye’s natural effort to focus, known as accommodation, and typically appears in early childhood. It is the most frequent type of inward eye turn diagnosed in children. The underlying issue is a mismatch between the need for clear vision and the resulting eye muscle activity.
The Mechanism of Inward Eye Turning
The root cause of accommodative esotropia is often uncorrected farsightedness, or hyperopia. To see clearly, the eye must adjust its internal lens through accommodation. This focusing effort is naturally tied to a reflex that causes the eyes to turn inward, called convergence.
In a person with significant farsightedness, the effort to accommodate and achieve clear vision is excessive. This constant, strong focusing drive triggers an over-response in the convergence reflex, leading to the eye turning inward. This physiological link is known as the accommodation-convergence reflex, where the ratio between the two responses is imbalanced.
Recognizing the Visual Signs
The onset of this acquired eye turn is typically observed between two and three years of age. Parents often notice that the eye crossing is intermittent at first, appearing most frequently when the child is focusing intently, is fatigued, or is ill. If left uncorrected, the inward turning may become constant.
Observable signs include obvious eye crossing toward the nose, which may alternate between the two eyes. Younger children might exhibit increased squinting or eye rubbing as they strain to focus. Older children may complain of blurred or double vision (diplopia) or experience headaches after visual tasks. Some children may also adopt an abnormal head posture, such as a head tilt or turn, to avoid double vision.
Confirming the Diagnosis
An eye care professional, such as a pediatric ophthalmologist or optometrist, confirms accommodative esotropia through a comprehensive eye examination. A critical step in the diagnostic process is performing a cycloplegic refraction. This procedure involves using specialized eye drops to temporarily paralyze the eye’s focusing muscle.
By relaxing the focusing muscle, the doctor can accurately measure the full amount of underlying farsightedness, or hyperopia, without interference from the patient’s own accommodation. The extent of the eye misalignment, or deviation, is measured using tests like the cover/uncover test and the alternate prism cover test. These measurements are taken at both distance and near to determine how the deviation changes with different focusing demands, helping to distinguish accommodative esotropia from other forms of strabismus.
Corrective Management Options
The primary treatment for accommodative esotropia is the full-time use of corrective spectacles. The goal is to prescribe the full hyperopic correction determined during the cycloplegic refraction. These glasses neutralize the farsightedness, which eliminates the need for the child to exert the excessive focusing effort that triggers the inward eye turn.
With the focusing demand removed, the eyes often align correctly within a few days to weeks of consistent spectacle wear. Full-time wear is emphasized, as removing the glasses allows the eye crossing to reappear. If the eye still crosses significantly when looking at near objects, the child may require bifocals.
Bifocals include a separate, stronger lens segment at the bottom to further relax the near-focusing effort. If decreased vision in one eye, known as amblyopia, has developed, patching therapy may also be prescribed. This involves covering the stronger eye to encourage the weaker eye to develop better vision. Surgery is typically reserved for cases where the glasses and bifocals do not fully correct the eye turn.