INTRODUCTION

Refractive accommodative esotropia is an intermittent or constant strabismus associated with uncorrected hyperopia.1 In patients with accommodative esotropia, the convergence mechanism is activated by the stimulation of the accommodative reflex, leading to a moderate to large angle-convergent strabismus. On examination, these patients typically have a hyperopic refractive error of 2.00D or greater.1–3

Accommodative esotropia has an estimated prevalence of 1% to 2% in the United States.1 Studies of the inheritance pattern of accommodative esotropia indicate that approximately 25% of accommodative esotropia patients’ first-degree relatives and 12% of second-degree relatives were affected. The high prevalence of accommodative esotropia among first- and second-degree relatives suggests a genetic component and possibly a preexisting sensory abnormality.2

Accommodative esotropia has an average age of onset at 2.5 years.3 It has been proposed that accommodative esotropia typically presents at this age as a result of patient interest in finer details compared with earlier in their life.4 This case series explores specifically the onset of accommodative esotropia prior to age 12 months. Although this phenomenon has been reported in literature, it is not the expected presentation.4–6 When esotropia presents prior to age 12 months, some practitioners may misdiagnose early onset accommodative esotropia as infantile esotropia and inappropriately recommend surgical intervention. This case series will also discuss the long-term binocular vision outcomes of these patients. No identifiable health information was included in this case report.

CASE REPORT 1

A boy aged 1 year and 1 month presented to clinic for his first eye examination with parent report of both eyes crossing at different times while viewing both distance and near objects since age 11 months. The patient was a dyzygotic twin and was born prematurely at 26 weeks gestation. His medical history was significant for dysphagia and bronchopulmonary dysplasia. The patient’s ocular history was significant for retinopathy of prematurity in both eyes, which resolved without treatment. There was no family history of amblyopia, strabismus, early childhood refractive error, or childhood onset ocular disease.

The patient’s initial examination revealed central, steady, and maintained vision in the right and left eye. Cover test revealed a comitant, 16– to 18–prism diopter variable, alternating, intermittent esotropia at distance and near. Extraocular movements were full in both the right and left eye, and no nystagmus was observed. The patient’s anterior segment was unremarkable. The patient was dilated with 1% cyclopentolate in both eyes. Cycloplegic retinoscopy revealed a refractive error of right eye +3.50 diopter sphere and left eye +3.25 diopter sphere. Posterior segment examination was unremarkable.

The patient was diagnosed with intermittent esotropia with a presumed accommodative component. He was given a spectacle prescription equivalent to the full cycloplegic retinoscopy for full-time wear and was instructed to return for follow-up to monitor alignment and visual acuity in 1 to 2 months.

At the patient’s follow-up examination 2 months later, his mother reported difficulty with compliance with spectacle wear after the patient spent 3 days in the hospital for a viral infection of his lungs. Prior to this hospital stay, however, the patient’s mother reported great compliance and good alignment of the eyes. On examination, the patient’s vision was central, steady, and maintained in each eye with his spectacles. Extraocular movements were full in each eye, and no nystagmus was observed. With his glasses, cover testing revealed that the patient’s eyes were aligned at distance and near.

The examination with spectacles confirmed the patient’s diagnosis of refractive accommodative esotropia. Because of the patient’s recent difficulty with spectacle wear, we counseled his mother on the importance of full-time spectacle wear and provided a prescription for 1% cyclopentolate, 1 drop in both eyes once daily, if he continued to have difficulty with spectacle wear. We recommended using cyclopentolate for no more than 1 week.

At the patient’s 2-month follow-up, his mother reported excellent spectacle wear compliance. His mother did not use cyclopentolate as he became accustomed to wearing his glasses again as a result of parental encouragement and return to typical daily routine. He had no esotropia with his spectacles on.

This patient has reliably followed with our clinics and is now 10 years old. At his most recent examination, his vision was 20/20 in each eye when tested with Snellen optotypes. He has never required amblyopia treatment. He showed normal central and peripheral fusion with Worth 4 Dot testing. Stereoacuity was 100 sec of arc with global stereo and 400 sec of arc with local stereo. His refractive error was right eye +5.25 - 1.75 x 180, left eye +5.00 - 1.25 x 005. His ocular health was unremarkable.

CASE REPORT 2

An infant aged 4 months 16 days presented to clinic because of parental concern of crossing of the eyes. Parents reported that both eyes crossed and that the crossing was becoming more frequent over time. The patient’s prenatal and birth history were insignificant, and she was meeting all developmental milestones as expected. There was no family history of amblyopia, strabismus, early childhood refractive error, or childhood onset ocular disease.

Initial examination revealed vision that was central, steady, and maintained in each eye. Cover testing revealed an 18– to 20–prism diopter variable, constant, alternating esotropia with near fixation. Distance fixation was unable to be assessed because of the patient’s young age and visual capabilities. Extraocular muscle movements were full in each eye, and no nystagmus was observed. The patient’s anterior segment was unremarkable. The patient was dilated with Cyclomydril (0.5% cyclopentolate and 0.5% tropicamide) in both eyes. Cycloplegic retinoscopy revealed a refractive error of right eye +7.50 diopter sphere and left eye +7.50 diopter sphere. Posterior segment examination was unremarkable.

Because of the presence of esotropia in the setting of high hyperopia, the decision was made to initiate glasses wear. A prescription was given equivalent to the full cycloplegic refraction, and the patient was advised to follow up in 2 months to monitor vision development and eye alignment.

The patient presented to clinic as recommended at the age of 6 months 17 days. Parents reported great compliance with her glasses. Vision assessment revealed central, steady, and maintained vision in each eye. Cover testing revealed orthophoria with glasses. The patient continued to have normal extraocular muscle movements and no nystagmus. The diagnosis of refractive accommodative esotropia was confirmed when the patient’s glasses were removed and she demonstrated an 18–prism diopter constant esotropia.

This patient has reliably followed with our clinics and is now 8 years old. At her most recent examination, her visual acuity assessed by Snellen optotypes was 20/25+2 in the right eye and 20/20 in the left eye. This patient never required amblyopia treatment as her acuity consistently measured within 1 line of equal. At some visits, her right eye was slightly decreased compared with her left, and at other visits her left eye was slightly decreased compared with her right. These acuity findings are consistent with her clinical presentation of a small-angle intermittent alternating esotropia. Subjective binocular vision assessment results included alternating intermittent peripheral and central suppression with Worth 4 Dot and 400 sec of arc with both global and local stereoacuity tests. Cover testing showed a 7–prism diopter intermittent alternating esotropia with distance and near fixation. Cycloplegic retinoscopy results were right eye +7.00 - 2.00 x 010, left eye +7.00 - 2.00 x 175. Her ocular health examination was unremarkable.

CASE REPORT 3

An infant aged 7 months 27 days presented to clinic with parental concern for crossing of the eyes, occurring since age 4 months. The crossing was reported to be worsening over time. The patient’s medical history was complex, including a diagnosis of cerebral palsy and periventricular leukomalacia secondary to premature birth at 29 weeks gestational age. He had history of retinopathy of prematurity, which resolved without treatment. Otherwise, his ocular health was unremarkable. There was no family history of amblyopia, strabismus, early childhood refractive error, or childhood onset ocular disease.

On initial examination, the patient was observed to be orthophoric with cover test with distance and near fixation. Visual acuity was recorded as fix and follow in each eye. The patient was dilated with cyclopentolate 1% in both eyes. Cycloplegic retinoscopy was right eye +3.50 diopter sphere, left eye +3.50 - 0.50 x 180. Ocular health was unremarkable. Because of no esotropia being observed during the examination, close observation was recommended.

At follow-up examination 2 months later, cover testing revealed a 16- to 20-prism diopter intermittent alternating esotropia with both distance and near fixation. Cycloplegic retinoscopy was right eye +3.50 diopter sphere, left eye +4.00 - 1.00 x 180. At this visit, glasses equivalent to the full cycloplegic refractive error were prescribed for full-time wear.

The patient returned for follow-up as scheduled in 6 weeks. On presentation with glasses, he was well aligned with cover test. In addition, his vision was central, steady, and maintained in each eye.

His clinical presentation was consistent throughout the first year of his life. Unfortunately, at 2 years old, the patient started to refuse glasses wear despite no changes in his refractive error. His esotropia decompensated over the next 2 years to a partially accommodative alternating esotropia, measuring 25 prism diopters with glasses and 35 prism diopters without, requiring strabismus surgery. He underwent a bilateral medial rectus recession. For 3 years postoperatively, he was well aligned with glasses. However, at his most recent examinations, at 6 years old, he manifested an intermittent exotropia. As with many intermittent exotropes, his control and angle of deviation has varied from visit to visit. The largest angle his intermittent exotropia has been recorded as is 30 prism diopters, whereas subsequent visits have shown exophoric posture. Because of developmental delays, he has not been able to participate in subjective binocular vision assessments. However, his visual acuity has remained central, steady, and maintained in each eye at all visits, never requiring amblyopia treatment.

DISCUSSION

These cases demonstrate accommodative esotropia with onset as early as age 4 months and the significant impact of glasses wear compliance on patient outcome. Accommodative esotropia may be misdiagnosed when first presenting at such a young age. However, because accommodation becomes more precise, reaching adult-like levels, as early as age 3 to 4 months, even age-normal amounts of hyperopia may induce accommodative esotropia at this very young age.6 Therefore, if esotropia is present in a patient with 2 diopters of hyperopia or greater, it has been recommended to first try glasses equivalent to the full cycloplegic refractive correction prior to any surgical interventions.7

In this series of case reports, the decision to prescribe the full cycloplegic refraction was made because of the presence of esotropia. Some practitioners prefer to reduce the prescribed hyperopia in such young infants because of concerns for interrupting emmetropization. However, studies have indicated that patients who present with accommodative esotropia do not emmetropize as an infant without accommodative ET would.8–10 In addition, it has been shown that there is, “a decrease in the odds of reaching +2.00D or less hyperopia by 18 months with increasing levels of hyperopia at 3 months.”8

Risk factors for accommodative esotropia include hyperopia, anisometropia, and abnormal ratio of accommodative convergence to accommodation. Birch has found that anisometropia increases the risk for accommodative ET 7 times in patients with +2.00 diopters of hyperopia and 2 times in children with +3.00 diopters of hyperopia.2 However, patients with +4.00 diopters of hyperopia are at no significant increased risk for accommodative esotropia if they also have anisometropia.2 Those patients with +4.00 diopters of hyperopia are already at a high risk for accommodative esotropia as a result of their significant hyperopia; therefore, anisometropia does not further increase that risk. Having an abnormally high ratio of accommodative convergence to accommodation also increases a patient’s risk for accommodative ET because even low amounts of hyperopia cause a greater amount of convergence. Interestingly, Birch found that a high ratio of accommodative convergence to accommodation alone had no deleterious effect on binocular vision and fine stereopsis.11

Treatment

Conventional treatment for accommodative ET includes prescribing glasses equivalent to the full cycloplegic retinoscopy results, with the goal of relaxing accommodation and eliminating the convergent strabismus while concurrently providing clear vision and reinstating the correct stimulus for improved binocular vision.

Strabismus surgery should not be used to treat accommodative ET because surgery does not treat the underlying refractive cause of the strabismus. If strabismus surgery is performed, the patient could potentially have a consecutive exotropia when also treated with the correct hyperopic spectacle prescription.1 However, those patients with partially accommodative ET may benefit from strabismus surgery that corrects the nonaccommodative component of their esotropia, as seen in case 3.

Contact lenses and refractive surgery are legitimate treatment options for patients who continue to manifest accommodative ET into the teenage years and adulthood as both of these treatment options address the underlying refractive cause of the strabismus. In addition, contact lenses may be considered in young patients who have difficulty with glasses compliance, although parents must be agreeable to the care and maintenance of the contact lenses.

Long-Term Prognosis

Binocular vision development has been shown to initiate at the age of approximately 3 months.12 Those patients with sensitive binocular systems can demonstrate accommodative esotropia at especially young ages. Koc et al showed in their retrospective report that 48.6% of patients presenting with hyperopia greater than 2 diopters and esotropia prior to age 6 months had resolution of their esotropia with glasses alone.12

Accommodative ET has 3 main outcomes following treatment with hyperopic correction: orthophoria, decompensation, or consecutive exotropia.13 If the patient is aligned with spectacle correction within a few months of onset of the esotropia, then long-term visual prognosis is good because of the correct stimulus for development of binocular vision and equal visual stimulation to each eye, decreasing the likelihood of amblyopia. However, there have been reports that 13% to 48% may decompensate to have a nonaccommodative esotropia in addition to the accommodative esotropia.1 This decompensated esotropia can result in loss of stereopsis and amblyopia. Those patients who are younger at the age of onset (2.5 years or younger) of the refractive accommodative esotropia, have oblique muscle dysfunction, delayed onset of treatment, or preexisting amblyopia are considered to be more likely to decompensate.11 Mohan and Sharma report that 10 years after initial correction of fully accommodative esotropia, 79% of patients had orthophoria or microesotropia (<10pd), 13% had consecutive exotropia, 5% decompensated to become a partially accommodative esotropia, and 3% converted to a high ratio of accommodative convergence to accommodation esotropia.14

As seen in case 1, initiating glasses at a young age ultimately led to good binocular vision, excellent eye alignment, and no amblyopia. In case 2, despite reportedly excellent compliance, the patient does not have perfect fusion, although she does maintain some level of stereopsis. However, as seen in case 3, if a patient has difficulty with glasses wear during the critical period of binocular vision development, the patient’s refractive accommodative esotropia is likely to decompensate. Of note, 2 of the presented cases were patients born prematurely. It has been reported that patients born prematurely are more likely to have abnormal binocular development.4 However, as seen in case 1, we may be able to help a patient have more typical binocular vision development if we intervene at first onset of esotropia. In addition, case 3 was complicated by the diagnoses of cerebral palsy and periventricular leukomalacia, which are known to negatively impact binocular vision development, and likely contributed to his decompensation.

Impact on Binocular Vision

Because accommodative esotropia presents at the average age of 2.5 years, this strabismus can have a significant impact on a patient’s stereoacuity development. The ideal accommodative esotropia patient presents to clinic while the esotropia is still intermittent and binocular vision is not significantly harmed. Unfortunately, this is often not the case. Birch, et al explains, “Periods of constant esotropia of >4 months duration, due to failure of spectacle treatment and/or noncompliance with spectacle wear, are associated with permanent stereodeficits even in patients who have normal stereoacuity at the onset of esotropia; thus, periods of abnormal binocular experience also may contribute to subnormal stereoacuity outcomes in accommodative esotropia.”11 Therefore, early treatment of accommodative esotropia, within 3 months of development of constant esotropia, is most beneficial to the development of fine stereopsis.14 Birch found that those patients with a constant esotropia greater than 4 months were 4.6 times more likely to have abnormal stereopsis compared with those patients who had a constant ET for 0 to 3 months.14 In addition, those patients whose constant esotropia lasted longer than 4 months were 33 times more likely to have no stereopsis compared with those with constant esotropia lasting 0 to 3 months.14

The clinical significance of these findings is demonstrated in the 3 cases presented in this series. Even patients who present to clinic within the recommended time frame of onset of esotropia may not achieve bifoveality. The reasons for this are multifactorial. First, there may be an inherent abnormality found in these patients’ binocular vision development, perhaps because of genetic variations.1 Also, for perfect stereoacuity development, the patient must be aligned during the majority of their binocular development period, which is most sensitive between the ages of 3 months and 4 years.7 It is unlikely that a patient will never lose, break, or refuse their glasses during this period of their life. Although the patient presented in case 2 reliably wore her glasses, there were short periods of time throughout her younger years in which she did not wear glasses, and she now has microesotropia. As seen in case 3, even a short period of glasses refusal can lead to a significant decompensation in esotropia.

CONCLUSION

This case series shows the importance of recognizing the clinical presentation of early onset refractive accommodative esotropia, prior to the age of 12 months, and correcting the angle of deviation with the full cycloplegic hyperopic spectacle prescription as soon as possible after the onset of deviation. Early treatment is the key to achieving the long-term goals of good binocular vision and eliminating amblyopia. It is important to monitor all accommodative esotropes regularly throughout the amblyogenic years, especially during the first 4 years of life when binocular vision is most vulnerable, to ensure patients have the correct spectacle prescription and maintain orthophoria. However, practitioners should also be mindful that even with the most compliant patients, bifoveal fusion may not be achievable, and alignment to microesotropia may be the ideal patient outcome.

TAKE HOME POINTS

  • Accommodative esotropia may have onset as early as 3 months of age.

  • One factor that determines binocular vision outcome in refractive accommodative esotropia is time between condition onset and treatment initiation (glasses) as well as compliance with glasses.

  • Even with the most compliant patients, those with accommodative esotropia may never achieve bifoveality.