Early Intervention in Refractive Accommodative Esotropia: A Case Report

Abstract:

Background: Refractive accommodative esotropia is a common strabismic condition caused by uncorrected hypermetropia, leading to excessive accommodative convergence and esodeviation. If left untreated, it can result in amblyopia and impaired binocular vision. Early diagnosis and intervention with optical correction and occlusion therapy play a crucial role in preventing long-term visual deficits.

Case Report: A 9-year-old female presented with complaints of dim vision and difficulty seeing the blackboard for six months. Clinical evaluation revealed bilateral hypermetropia (+6.50 DS), significant esotropia, and bilateral ametropic amblyopia. Full hyperopic correction was prescribed to reduce accommodative demand, and part-time patching therapy (2:1 ratio for OD:OS) was initiated to improve visual acuity. Follow-up assessments showed significant improvement, with visual acuity reaching OD: 6/9 and OS: 6/6, and esodeviation reducing to orthophoria for distance and minimal deviation for near. Patching was discontinued, and the patient was advised to continue spectacle correction with regular monitoring.

Conclusion: This case highlights the effectiveness of early optical correction and occlusion therapy in managing Refractive accommodative esotropia and amblyopia. Timely intervention not only restores visual acuity but also helps maintain binocular single vision and long-term ocular alignment. Regular follow-ups are necessary to monitor treatment stability and prevent recurrence.

Keywords: Refractive accommodative esotropia, hypermetropia, amblyopia, binocular vision

Background:

Accommodative esotropia is the most common form of all childhood strabismus (Mohney, 2001; Mohney & Huffaker, 2003). In accommodative esotropia, excessive convergence arises either from a physiological response (accommodative convergence) to significant hypermetropia or an aberrant response (elevated accommodative convergence to accommodation ratio) to mild hypermetropia (Birch, 2003). Timely diagnosis and suitable optical correction can enhance binocular vision and prevent amblyopia. Numerous investigations on the treatment results of accommodative esotropia have encompassed individuals exhibiting either a high accommodative convergence to accommodation (AC/A) ratio or those with partially accommodative esotropia (Black, 2006; Mohney et al., 2011; Mulvihill et al., 2000). The mean onset age of accommodative esotropia is 2.5 years, with a broad spectrum ranging from three months to seven years (Baker & Parks, 1980; Berk et al., 2004; Pollard & Greenberg, 2002). The overall incidence of Accommodative esotropia is 50.3 cases per 100,000 children younger than 19 years (Mohney, 2007). Accommodative esotropia can be entirely refractive (no strabismus persists after correcting hypermetropia) or partially refractive (the esotropia diminishes with refractive correction but remains evident). Additional complicating factors, including vertical deviations (predominantly inferior oblique overaction accompanied by superior oblique underaction) and amblyopia, may be present as causes, effects, or associations with esotropia (Liang & Fricke, 2006). The accurate differential diagnosis of esotropia is crucial for effective therapy of the deviation. The differential diagnosis of AET includes pseudo-esotropia, infantile or congenital esotropia, sensory esotropia, acquired nonaccommodative esotropia, incomitant esotropia, and esotropia in the neurologically impaired child (Rutstein, 2008).

Refractive accommodative esotropia, or fully accommodative esotropia, is characterized as an esotropia that is completely cured at both distance and near when the patient uses a hyperopic correction. With timely and suitable therapy in 90% of all instances, normal binocular vision with high-grade stereopsis (60 seconds of arc or better) is most likely (Wilson et al., 1993). It generally starts as an intermittent and fluctuating esotropia. Parents often see that their child's eyes are aligned at times but converge when the child is fatigued or concentrating on nearby objects. Eyeglasses are prescribed based on the severity of hyperopia, and any accompanying amblyopia is also addressed (Mulvihill et al., 2000). Certain ophthalmologists, however, recommend early surgical surgery for this condition (Gobin, 1991).

Although many research has examined refractive accommodative esotropia and bilateral ametropic amblyopia therapy, the long-term success of various approaches is unknown. Most research focuses on early optical correction and patching therapy, but limited is known about patching duration and whether atropine penalization or other amblyopia treatments work as well. While full hyperopic correction is the conventional treatment, partial hyperopic correction may improve adaption and minimize glasses need in some individuals. Studies rarely follow up after childhood, therefore the long-term stability of binocular vision post-treatment is another significant gap. Further study is needed to assess the neuroplasticity of binocular vision recovery, the relevance of modern optical therapies such bifocal and progressive addition lenses (PALs), and the psychosocial effects of early esotropia correction on children's development. Gaps can be filled to improve treatment and patient outcomes.

Case Report:

A 9-year-old female was referred for squint evaluation with complaints of dimness of vision, difficulty seeing the blackboard for the past 6 months. Her parents also noticed an inward deviation of her eyes. She had no history of previous ophthalmic consultation, spectacle use, ocular disease, trauma. Her parents reported no abnormal birth history. 

Diagnostic Procedure:

1. Visual Acuity Testing: The patient's unaided visual acuity was assessed using a Snellen chart for both distance and near vision. In this case, the right eye (OD) had a visual acuity of 4/60, which improved to 6/60 with a pinhole, while the left eye (OS) had a visual acuity of 6/60, improving to 6/18 with a pinhole. Near visual acuity was N8 at 30 cm in both eyes.

2. Objective Refraction: Objective refraction using retinoscopy showed high hypermetropia (+6.00 DS in both eyes).

3. Subjective Refraction: After objective refraction, subjective refraction was conducted to determine the best-corrected visual acuity. The final prescription was OD: +4.50 DS (VA 6/60) and OS: +6.00 DS (VA 6/18).

4. Cycloplegic Refraction: The results indicated OD: +6.50 DS and OS: +6.50 DS, which was slightly higher than the subjective refraction values. This procedure is particularly important in children with accommodative esotropia, as it prevents over-accommodation from masking the full extent of hypermetropia.

5. Orthoptic Evaluation: The cover test (CT) indicated right esotropia, which changed to an alternate convergent squint during the alternate cover testing. The prism bar cover test (PBCT) measured the deviation, revealing 28Δ base-out (BO) for distance and 40Δ BO for near without corrective lenses. The deviation decreased to 18Δ BO for distance and 32Δ BO for near with the use of glasses. These tests facilitated the confirmation of the diagnosis of refractive accommodative esotropia and evaluated the extent of misalignment.

6. Ocular Motility: Ocular motility was evaluated to rule out any restrictions or muscle weaknesses. The patient demonstrated full extraocular movements in both eyes, indicating no mechanical limitations or paralytic components contributing to the esotropia. 

7. Anterior and Posterior Segment Examination: A detailed slit lamp examination of the anterior segment and fundus examination of the posterior segment were performed. Both were within normal limits (WNL), ruling out structural abnormalities or pathologies that could contribute to the visual complaints. Central fixation was confirmed in both eyes using an ophthalmoscope grid pattern, indicating no fixation anomalies.

Diagnosis:

The patient was diagnosed with Refractive Accommodative Esotropia accompanied by Bilateral Ametropic Amblyopia, resulting from uncorrected hyperopia that induced excessive accommodative convergence and inward ocular deviation. The diagnosis was confirmed by diminished esodeviation with complete hyperopic correction, the existence of binocular single vision, and normal ocular health. Timely management was crucial to avoid prolonged vision deterioration and preserve binocular function.

Prognosis:

The prognosis for refractive accommodative esotropia is generally favorable with timely intervention. Full correction of hypermetropia and patching therapy can lead to significant improvement in visual acuity and alignment of the eyes. However, long-term follow-up is essential to monitor for recurrence and ensure the maintenance of binocular single vision.

Treatment plan:

 1. Refractive Correction (Glasses): The patient was given spectacles with the full cycloplegic refraction prescription (+6.50 DS in both eyes) to relax accommodation and reduce excessive accommodative convergence. Glasses help realign the eyes, improve visual acuity, and prevent further progression of amblyopia.

 2. Patching Therapy: To address the bilateral ametropic amblyopia, part-time patching therapy was initiated. The patching regimen followed a 2:1 ratio (OD: OS), with the right eye patched for twice as long as the left eye, totalling 4-6 hours daily. 

 3. Follow-Up and Monitoring: The patient was scheduled for regular follow-ups to monitor progress. At the 2-week follow-up, visual acuity had improved to OD: 6/24 and OS: 6/9p, and the deviation reduced to 12Δ BO for distance and 18Δ BO for near. By the 1-month follow-up, further improvement was noted, with visual acuity reaching OD: 6/9 and OS: 6/6, and near deviation reduced to 8Δ BO. 

4.  Parental Counseling: Parents were educated about the importance of compliance with glasses and patching therapy. They were informed about the potential risks of non-compliance, such as persistent amblyopia and recurrence of esotropia. Parental involvement is crucial to ensure the child adheres to the treatment plan, especially in cases requiring long-term management like amblyopia and strabismus.

5.  Long-Term Management: The patient was advised to continue wearing the prescribed glasses and attend follow-up visits every 6 months. Long-term management is essential to ensure the stability of ocular alignment and visual acuity. Regular monitoring helps detect any changes in refractive error or recurrence of strabismus, allowing for timely intervention if needed.

Discussion:

Refractive accommodative esotropia is a prevalent etiology of childhood strabismus, frequently linked to unaddressed hypermetropia. The patient exhibited significant hypermetropia and esotropia, resulting in amblyopia. The prompt administration of complete hyperopic correction and occlusion therapy led to significant enhancement in visual acuity and ocular alignment. The treatment goal is to align the eyes early, improve visual acuity, and maintain binocular single vision. In this case, full hyperopic correction significantly reduced the esotropia and improved visual acuity. Patching therapy addressed the amblyopia, leading to successful outcomes. This instance underscores the significance of early refractive correction and amblyopia treatment in children. Consistent follow-up and parental education are essential to guarantee compliance and eliminate recurrence.

Conclusion:

This case emphasizes the significance of immediate attention in refractive accommodative esotropia. Comprehensive hyperopic correction, occlusion therapy, and parental guidance were crucial in attaining favorable visual results. Optometrists play a crucial role in the early identification and care of these instances, facilitating the development of normal binocular function in children and preventing long-term visual problems. Prolonged monitoring is crucial to detect recurrence, preserve binocular single vision and quality of life

This report possesses multiple limitations. As a single case study, the results may not be applicable to all patients with refractive accommodative esotropia and amblyopia. The short follow-up duration (1 month) constrains the evaluation of long-term outcomes, including the stability of ocular alignment and visual acuity. The lack of a control group or comparison analysis complicates the identification of the most effective treatment method. Advanced diagnostic instruments, including OCT, were not employed, and genetic or systemic causes were not investigated. The psychosocial effects of the disease and its treatment on the patient and family were not considered. reducing these limitations in subsequent investigations might enhance the comprehension and management of Refractive accommodative esotropia and amblyopia.

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