Effective Vision Therapy for Convergence Excess and BVD Mahadani_s

Effective Vision Therapy for Convergence Excess and Binocular Vision Dysfunction: A Case Report

ABSTRACT

Background: Convergence excess (CE) is a binocular vision disorder characterized by an over-convergence response at near distances, leading to symptoms such as eyestrain, headaches, blurred vision, and diplopia. Early identification and personalized management through vision therapy are essential for improving visual comfort and function.

Case Report: A 22-year-old male presented with persistent eyestrain, frontal headaches, and blurred vision during sustained near tasks. A comprehensive binocular vision assessment revealed convergence excess, accommodative lag, and reduced negative fusional vergence. A structured 12-week vision therapy program was implemented, resulting in significant improvements in symptomatology and binocular vision parameters.

Conclusion: This case emphasizes the importance of detailed binocular vision assessment in symptomatic patients and the effectiveness of personalized vision therapy in managing convergence excess and associated dysfunctions.

Keywords: Convergence excess, binocular vision, esophoria, vision therapy, accommodative dysfunction.

Background

Convergence excess (CE) is a binocular vision anomaly where the eyes tend to converge more than necessary during near fixation, resulting in esophoria or esotropia at near. About one-third of children with horizontal strabismus exhibit convergence excess (Arnoldi, 1999). The phrase 'convergence excess esotropia' refers to an esotropia that appears greater at near fixation compared to distance fixation, first defined by Donders in 1864 (Ansons & Davis, 2008; Donders, 1864). Surgery is often eventually needed for most patients with convergence excess esotropia. Convergence excess is often associated with a high accommodative convergence/accommodation (AC/A) ratio, accommodative lag, and reduced negative fusional vergence (NFV) at near. Clinical symptoms commonly include eyestrain, headaches, blurred vision, and intermittent diplopia during tasks that require prolonged near focus, such as reading or computer use (Awadein et al., 2023). The excess of vergence is frequently linked to accommodative insufficiency The eyes are directed inward more than intended to compensate for diminished focus endurance or capability (Mensah, 2016). This results in a disparity between vergence and focus, hence impacting the clarity of binocular vision.

Studies have indicated that CE may impact academic and occupational performance, particularly in populations engaged in extended periods of close work (SCHEIMAN et al., 2005). Vision therapy has been shown to be effective in reducing symptoms, improving NFV, and enhancing accommodative control in patients with CE (Gallaway & Scheiman, 1997). Early diagnosis and tailored therapeutic interventions can significantly improve visual efficiency and quality of life. The management and correction of the disease rely on comprehending the underlying cause in each specific instance and implementing appropriate corrective or alleviative interventions (TAIT, 1956).

Case Report

A 22-year-old male university student presented with complaints of persistent eyestrain, frontal headaches, and intermittent blurring of vision during prolonged reading and digital device use. Symptoms had been present for approximately eight months and were progressively worsening. There was no significant ocular or systemic medical history. Visual acuity was 20/20 in both eyes with no refractive correction required.

Diagnostic Procedure

A comprehensive binocular vision evaluation was conducted, yielding the following findings:

1. Visual Acuity Assessment: Visual acuity was measured using a Snellen chart at both  distance and near, revealing 20/20 vision in each eye.

2. Cover Test: Near and distance cover tests were performed, revealing a 6 prism diopters esophoria at near fixation, orthophoria at distance.

3. Maddox Rod: The Maddox Rod Test was performed to assess phoria, revealing an eso deviation of 5 prism diopters at near.

4. Near Point of Convergence (NPC): The NPC was measured using a pen torch and reg/green goggles, showing an initial break at 5 cm and recovery at 7.5 cm.

5. AC/A Ratio: High 7.9:1 (IPD = 5.5 cm, NFD = 0.4 m, near phoria = +6∆, distance phoria = 0∆)

6. Negative Fusional Vergence (NFV): NFV was measured using a prism bar, revealing a break point of 4 prism diopters of base-in.

7. Positive Fusional Vergence (PFV): PFV was measured using a prism bar, revealing a break point of 12 prism diopters of base-out.

8.     Near Point of Accommodation (NRA): NRA was measured using the push-up method, revealing a range of 3 diopters.

9.     Positive Relative Accommodation (PRA): PRA was measured using the push-up method, revealing a range of 2 diopters.

10.  Amplitude of Accommodation (AOA): AOA was measured using the push-up method, revealing an amplitude of 12 dioptres.

11.  Monocular Estimation Method (MEM): MEM was performed to assess the patient's ability to estimate distance accurately, revealing +1.25 D lag

12.  Accommodative Facility: Accommodative facility was assessed using flipper lenses, revealing a facility of  6 cycles per minute (cpm) binocular with ±2.00 D flippers

13.  Vergence Facility:  Vergence facility was assessed using flipper lenses, revealing a facility of 8 cycles per minute with 12∆ BO / 3∆ BI flippers

14.  Stereopsis: 40 seconds of arc (Randot Stereotest)

15.  Extraocular Movements (EOM): EOM were assessed to rule out any muscle weakness or restriction.

Diagnosis

The patient showed

·  Significant esophoria at near

·  High AC/A ratio

·  Difficulty clearing minus lens

·  Accommodative lag

·  Reduced negative fusional vergence

These findings confirmed a diagnosis of convergence excess predominantly affecting near visual tasks, correlating with the patient’s symptoms.

Prognosis

The prognosis for visual comfort and binocular vision function was considered favorable with a structured vision therapy plan. The patient was highly motivated, and good compliance was anticipated. Early diagnosis and tailored treatment plans are crucial for achieving optimal outcomes

Treatment Plan

A 12-week in-office vision therapy program, supported by home exercises, was initiated. The plan was divided into three progressive phases:

Phase 1 (Weeks 1–4): Foundational Vision Therapy

During the initial four weeks of treatment, the primary focus will be on establishing baseline measurements and introducing fundamental vision therapy exercises. This phase is essential for understanding the patient's current binocular vision status and laying the groundwork for subsequent therapy.

·  Brock String Exercises for vergence awareness: Brock string exercises were incorporated to enhance divergence control. The patient focused on the farthest bead while maintaining single binocular vision, encouraging the eyes to align more comfortably for distance. This exercise was performed daily to reinforce divergence habits. 

·  Base-in training with loose prisms: Divergence training was initiated using loose prism glasses to reduce the patient’s excessive convergence tendency. The patient practiced relaxing convergence while viewing a target through base-out prisms, gradually increasing the prism power as tolerance improved

·  Computerized vergence training program: Interactive vergence training software (e.g., HTS) was incorporated, providing dynamic visual stimuli to enhance vergence flexibility and vergence break/recovery thresholds.

·  Accommodative rock with ±2.00 D flippers: Binocular accommodative facility was trained using ±2.00 diopter flipper lenses while the patient read N8 print at 40 cm. This improved both accommodative response and the patient's ability to switch focus across various distances, addressing the accommodative lag noted during baseline testing.

·  Barrel Card and Hart Chart: The Barrel card, used monocularly and binocularly, encouraged awareness of near-point alignment and promoted voluntary divergence. Concurrently, the Hart Chart was employed at both near and distance to stimulate accommodative-vergence accuracy through alternating distance tasks.

 Phase 2 (Weeks 5-8 ): Vergence and Accommodation Strengthening

During weeks five to eight, the focus will shift to intensive vision therapy aimed at strengthening divergence and accommodation skills. The goal is to further enhance binocular vision function through targeted exercises and activities.

·  Vectograms with base-in demand: The patient worked with vectograms (e.g., Quoit) and red-green tranaglyphs, gradually increasing base-in prism demands to improve NFV and simultaneous vergence facility. Fusional lock cues were reduced over time to challenge binocular fusion.

·  Bug on string exercise: This kinaesthetic-based activity enhanced the patient’s proprioceptive awareness of eye posture. While visualizing an imaginary "bug" crawling along a string away from their nose, the patient practiced slow, conscious divergence, facilitating internal control of convergence relaxation.

·  Near-Far Hart Chart Reading: The patient alternated reading words between a near Hart chart (held at 40 cm) and a distant one (at 3–4 meters). This activity trained accommodative flexibility and vergence transitions, reinforcing coordination between systems.

·  Aperture rule training: Divergence ability was further enhanced through use of the Aperture Rule with 2-aperture cards. Starting with easier divergence targets (e.g., cards 1–4), the patient progressed through increasing levels of base-in demand over time, with improvements noted in fusion duration and clarity.

Phase 3 (Weeks 8–10): Integration and Binocular Stability

In the final phase of treatment, weeks nine to twelve will focus on consolidating gains made in previous phases and transitioning to more advanced binocular vision exercises to enhance overall binocular vision function.

·  Lifesaver cards: Lifesaver cards were used to practice fusion and anti-suppression in free space without instrument assistance. The patient reported significant improvement in maintaining fusion, and this exercise helped bridge the gap between clinical tasks and daily visual demands.

·  Jump vergence training with variable fixation distances: Using alternating near and far fixation targets (including letter charts and flashing stimuli), the patient performed rapid shifts in focus and vergence. The activity promoted quick and accurate adjustment of ocular alignment under naturalistic viewing conditions.

·  Eccentric circles and Free space fusion cards: The patient practiced divergence with eccentric circle cards to further solidify base-in fusion ability. These activities required precise alignment of free-space targets, enhancing fusional accuracy and stereopsis.

·  Task oriented visual stimulation: In the final weeks, therapy incorporated real-life tasks such as reading small-print material, sketching architectural diagrams, and screen-based activities. During these tasks, the patient used strategies learned in earlier phases (e.g., taking divergence breaks, applying flipper lens training) to reinforce stable visual comfort during prolonged near work.

Pre & Post-Treatment Findings

Discussion

Convergence excess is often underdiagnosed in routine clinical practice, especially in young adults presenting with non-specific symptoms such as eyestrain and headaches. In this case, a detailed binocular vision assessment revealed CE associated with accommodative lag and fusional vergence deficits. A personalized vision therapy program led to significant symptomatic relief and functional improvement, reinforcing the importance of individualized, evidence-based intervention strategies. Vision therapy for convergence excess should be regarded as a successful treatment modality, either in conjunction with additional lenses or as a standalone intervention for patients who choose not to use lenses or find them impractical (Gallaway & Scheiman, 1997). Also, (GRISHAM et al., 1991) and (Wick, 1977) each reported a case of convergence excess that showed increased NFV and reduces symptoms after vision therapy.

Research by Gallaway & Scheiman (1997) has demonstrated the efficacy of vision therapy in CE, particularly in improving NFV and accommodative control. This case adds further support to the clinical value of structured in-office therapy for convergence excess.

Conclusion

This case underscores the importance of comprehensive binocular vision assessment in symptomatic individuals and demonstrates that structured vision therapy can yield significant improvements in convergence excess. Early diagnosis and an individualized approach are key to enhancing visual efficiency and overall quality of life.

This case report has several limitations. Firstly, accommodative function was assessed only through subjective clinical methods without objective confirmation such as dynamic retinoscopy or autorefractor measurements. Additionally, cycloplegic refraction was not performed, which could have ruled out latent hyperopia influencing the high AC/A ratio. The absence of long-term follow-up limits insight into the sustained efficacy of the management plan. Moreover, no advanced imaging or functional eye-tracking tools were used to further analyze binocular vision behavior. As a single case, the findings cannot be generalized to a broader population.

References

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Awadein, A., Gouda, J., Elhilali, H., & Arnoldi, K. (2023). Convergence Excess Esotropia: Review. Journal of Binocular Vision and Ocular Motility, 73(4), 131–159. https://doi.org/10.1080/2576117X.2023.2261155

Donders, F. C. (1864). On the anomalies of accommodation and refraction of the eye. New Sydenham Society.

Gallaway, M., & Scheiman, M. (1997). The efficacy of vision therapy for convergence excess. Journal of the American Optometric Association, 68, 81–86.

GRISHAM, J. D., BOWMAN, M. C., OWYANG, L. A., & CHAN, C. L. (1991). Vergence orthoptics: validity and persistence of the training effect. Optometry and Vision Science, 68(6), 441–451.

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TAIT, E. F. (1956). Some factors in the diagnosis and treatment of accommodative convergence excess. The American Orthoptic Journal, 6, 90–97. https://doi.org/10.1080/0065955x.1956.11981171

Wick, B. (1977). Binocular vision therapy for general practice. Journal of the American Optometric Association, 48(4), 461–466.

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