Accommodative esotropia is an inward deviation of the eyes caused by accommodative convergence associated with accommodative effort. The underlying factor is moderate to high hyperopia. The angle of deviation decreases with full refractive correction.
It is the most common type of acquired esotropia. It accounts for about one-third of all strabismus patients, with a prevalence estimated at 1-2% of the population. There is no gender or racial predilection. Onset is most common between 1 and 3 years of age, but can occur from 4 months to 7 years.
Hyperopia of +2D or more predisposes to onset. It is rare with +8D or more. The average hyperopia in pure accommodative esotropia is +5.43D ± 2.25. The most common age of onset is around 1.5 to 3 years, when visual acuity develops and clear vision is actively sought. Rarely, early onset before 6 months of age may occur, requiring differentiation from infantile esotropia.
Since onset is at a young age, complaints of double vision are rare. The following symptoms may be observed.
Accommodative esotropia presents as comitant esotropia. Cycloplegic refraction is essential for diagnosis.
Refractive
Orthophoria with full correction: The eye position becomes orthophoric with glasses that fully correct hyperopia.
Normal AC/A ratio: The angle of deviation is similar for distance and near.
Angle of deviation: Usually 20–40 prism diopters (PD).
Binocular vision: Generally good.
Non-refractive
Partially accommodative
Residual esotropia: With full correction, the strabismus angle decreases by 10 PD or more, but residual esotropia of 10 PD or more persists.
Mixed type: Accommodative and non-accommodative esotropia coexist.
Surgical indication: Surgery is considered for residual esotropia.
Binocular visual function: Varies, often poor.
Associated with moderate hyperopia (usually +2.00 to +6.50 D). In the early stages, intermittent inward deviation is observed, which may gradually become constant. Unilateral amblyopia may be present.
The underlying cause of accommodative esotropia is excessive accommodative convergence associated with accommodative effort.
In hyperopia, accommodation is required to obtain a clear image. Accommodation stimulates convergence. Esotropia develops when fusional divergence cannot fully compensate for this convergence.
Due to an abnormally high AC/A ratio (accommodative convergence to accommodation ratio), convergence becomes excessive relative to the amount of accommodation at near. It can occur regardless of the type of refractive error.
For the diagnosis of accommodative esotropia, cycloplegic refraction and eye alignment assessment are essential.
In pediatric refraction, cycloplegic agents are mandatory due to significant accommodative interference.
If the difference between distance and near deviation angles is 10 PD or more, suspect a high AC/A ratio.
| Method | Procedure | Normal value |
|---|---|---|
| Gradient method | Change in deviation angle after +3 D addition ÷ 3 | 4 ± 2 PD/D |
| Heterophoria method | Difference between distance and near deviation angles plus interpupillary distance | 4 ± 2 PD/D |
After wearing fully corrective glasses for at least 3 months, the following criteria are used.
The time for eye alignment to stabilize after wearing glasses varies by case. In many cases, it stabilizes within 3 months, but sometimes it takes longer. The assessment should be made carefully while monitoring the use of glasses.
The goals of treatment are to restore normal eye alignment, promote binocular vision development, and prevent or treat amblyopia.
Wearing fully corrective glasses is fundamental. Prescription is based on cycloplegic refraction values (atropine sulfate eye drops are first choice in children). For pure accommodative esotropia, instill 0.5% atropine three times daily for 3–5 days, and prescribe fully corrective glasses or glasses with 0.5D less power. Full-time wear is essential, and care must be taken to prevent the frame from slipping. If orthophoria is achieved for both distance and near with fully corrective glasses, surgery is not indicated.
For distance, full refractive correction is used; for near, prescribe bifocal or progressive addition lenses with +2.5 to +3.0D addition. Prescribe the minimum addition (up to +3.00D) that restores normal ocular alignment at near. The AC/A ratio may normalize with growth, and 37–62.5% of patients can switch from bifocals to single-vision glasses or become spectacle-independent by age 8–12. Another option is drug therapy with distigmine bromide (Ubretid eye drops 1%), which reduces the AC/A ratio via cholinesterase inhibition.
Wearing fully corrective glasses is first-line treatment. Since hyperopia may increase in children under 7, repeat cycloplegic refraction before surgery to confirm no undercorrection. Surgery is performed only for the residual deviation while wearing glasses.
About 30% of patients require surgery in addition to refractive correction. Surgery is considered under the following conditions:
Main surgical procedures are as follows:
Even after surgery, continued spectacle wear for refractive correction is necessary. Since esotropia with hyperopia may shift to exotropia with age, surgery should be decided carefully.
It is sometimes used as chemical denervation for partially accommodative esotropia. Although the risk of consecutive exotropia is considered low, some reports indicate that incisional surgery yields better outcomes.
If amblyopia is present, treatment should be started promptly. Patching of the healthy eye is the basic approach, and it should be initiated as soon as the diagnosis is confirmed.
Hyperopia tends to decrease with growth. However, only about 15% of patients can maintain orthophoria without glasses in the long term. The remainder either continue to have refractive accommodative esotropia or transition to partially accommodative esotropia.
The mechanism of accommodative esotropia is based on the near response triad of accommodation, convergence, and miosis.
In hyperopic eyes, accommodation (increase in lens curvature) is required to form a clear image on the retina. Accommodation is accompanied by accommodative convergence. Normally, fusional divergence offsets this excess convergence and maintains orthophoria.
When hyperopia is moderate or higher (usually +2.00 D or more), the required accommodation increases, and accommodative convergence increases proportionally. Esotropia becomes manifest when the compensatory capacity of fusional divergence is exceeded. The AC/A ratio itself is within the normal range (4±2 PD/D), but the absolute amount of convergence becomes excessive due to the large accommodation.
Because the AC/A ratio is abnormally high (6 PD/D or more), the convergence response per unit of accommodation is excessive. Since near vision requires more accommodation than distance vision, the near deviation is markedly inward. It can occur regardless of the type of refractive error.
Newborns have about +2 D of hyperopia. Hyperopia increases until around 7–8 years of age and then decreases by around 20 years of age. This increase and decrease in hyperopia affects the onset and course of accommodative esotropia. There is also an early-onset type that develops before 1 year of age, which requires differentiation from infantile esotropia.
In constant esotropia, images from the deviated eye are suppressed in the cerebral cortex. When fixation is biased to one eye, sustained suppression of the non-dominant eye occurs, leading to strabismic amblyopia. If alternating fixation is present, visual acuity develops equally in both eyes.
Accommodative esotropia is the most common type of acquired esotropia 1), and the benefit of eye position improvement through hyperopic correction is significant. It has been suggested that eye position correction for amblyopia treatment may lead to spontaneous improvement of amblyopia 1).
As a new approach to strabismic amblyopia, treatment methods using binocular vision are being researched. Methods that separate the visual elements of both eyes and encourage attention to the amblyopic eye are being investigated. However, the mechanism is not yet understood, and well-designed controlled studies are needed 1).
For adult accommodative esotropia, there are attempts to correct hyperopia with excimer laser LASIK or PRK to achieve spectacle independence. However, adaptation for children has not been established.
