Background: 

Convergence insufficiency (CI) is characterized by difficulties with coordinating the eyes to converge and sustain alignment when fixating on proximal objects, leading to symptoms such as ocular strain, diplopia, and headaches. Eso deviation, or esophoria, refers to an inward misalignment of the eyes at rest, which complicates the convergence of the eyes during near tasks. Impaired stereopsis, or depth perception, is common in individuals with convergence insufficiency, as the brain attempts to merge the disparate images from each eye due to deficient binocular vision. In research using established definitions of CI, researchers have documented a prevalence ranging from 4.2% to 6% in educational and clinical environments (ROUSE et al., 1998, 1999; Scheiman et al., 1996). Accommodative dysfunction, another symptom of CI, emerges as an inability to properly alter the focus of the eyes for close vision, causing fuzzy vision and visual discomfort. Numerous research has investigated the occurrence and effect of CI and related visual dysfunctions. Notably, research by (Rouse et al., 2004) , and (SCHEIMAN et al., 2005) have underlined the prevalence of CI and its negative impact on academic performance and quality of life. Furthermore, (Ament et al., 2008) and (Gallaway & Scheiman, 1997) have demonstrated the effectiveness of vision therapy in reducing symptoms and increasing visual performance in people with CI and associated binocular vision problems. These findings highlight the need of early identification and focused management for convergence insufficiency (Lavrich, 2010), eso deviation, diminished stereopsis, and accommodative dysfunction, which improves overall visual comfort and performance during close activities. Considerable uncertainty persists concerning the optimal treatment for CI. Recommended interventions include: base-in prism reading glasses, home-based pencil push-ups, home-based vision therapy/orthoptics, and office-based vergence/accommodative therapy (Chin et al., 1995; Gallaway & Scheiman, 1997; GRISHAM, 1988).

While vision therapy has demonstrated potential in addressing convergence insufficiency (CI) and binocular vision impairment, numerous research gaps remain. The data on the long-term efficacy of these therapies is limited, as most studies do not include extensive follow-up periods. Furthermore, comparison analyses are required to assess the efficacy of various treatment modalities, including office-based therapy in contrast to home-based exercises or prism spectacles. Moreover, the absence of a standardized protocol for vision therapy results in inconsistencies in treatment methodologies and outcomes. Further research is required to investigate the effects of CI on particular demographics, including children with learning disabilities and adults with digital eye strain, as well as to create more accessible and scalable therapeutic alternatives.

Case Report:

A 25-year-old male presented with complaints of eyestrain, intermittent diplopia, and difficulty focusing, especially during prolonged near tasks such as reading and using electronic devices. Visual acuity was 20/20 in each eye. The patient reported no significant ocular or medical history. Based on the reported symptoms, the patient was referred for a comprehensive binocular vision assessment.

Diagnostic Procedure:

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 4 prism diopter exophoria at near fixation.

3. Maddox Rod Test: The Maddox Rod Test was performed to assess phoria, revealing an eso deviation of 2 prism diopters.

4. Stereopsis: Stereopsis was assessed using the Randot Stereotest, revealing reduced stereopsis of 60 seconds of arc.

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

6. Near Point of Convergence (NPC): The NPC was measured using a penlight, showing an initial break at 10 cm and recovery at 7 cm.

7. Near Fusion Range (NFR): The patient's ability to maintain single binocular vision within a range of fusional vergence was assessed, revealing a range of 12 prism diopters of base-out to 8 prism diopters of base-in.

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

9. Negative Fusional Vergence (NFV): NFV was measured using a prism bar, revealing a break point of 8 prism diopters of base-in.

10. Near Point of Accommodation (NRA): NRA was measured using the push-up method, revealing a range of 5 diopters.

11. Positive Relative Accommodation (PRA): PRA was measured using the push-up method, revealing a range of 3 diopters.

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

13. Monocular Estimation Method (MEM): MEM was performed to assess the patient's ability to estimate distance accurately, revealing accurate distance estimation.

14. Accommodative Facility: Accommodative facility was assessed using flipper lenses, revealing a facility of 10 cycles per minute.

15. Vergence Facility: Vergence facility was assessed using flipper lenses, revealing a facility of 12 cycles per minute.

Diagnosis: 

The patient was diagnosed with convergence insufficiency, eso deviation, reduced stereopsis, and accommodative dysfunction (Scheiman et al., 2008). These findings indicate impaired binocular vision function, particularly during near tasks.

Prognosis: 

The prognosis for symptom improvement and binocular vision function is favourable with suitable vision therapy. The patient may necessitate continuous monitoring and maintenance therapy to preserve enhancements. Early diagnosis and tailored treatment plans are crucial for achieving optimal outcomes

Treatment Plan:

The treatment plan involved vision therapy sessions twice a week for 12 weeks, divided into three phases:

Phase 1 (Weeks 1-4): Establishing Baseline Measurements and Introducing Basic Vision Therapy Exercises.

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.

1. Baseline Assessment: Comprehensive measurements of convergence ability, accommodation, and fusional vergence will be conducted to establish baseline values for comparison throughout the treatment process.

2. Basic Vision Therapy Exercises:

·  Pencil Push-Ups: The patient will perform pencil push-up exercises to improve convergence ability. This exercise involves focusing on a pencil held at arm's length and slowly bringing it closer to the nose while maintaining single binocular vision.

·  Brock String Exercises: Using a Brock string, the patient will practice convergence and divergence by focusing on beads along the string at various distances.

·  Computerized Vergence Training: Interactive computerized programs will be utilized to provide targeted training for improving fusional vergence and binocular coordination.

Phase 2 (Weeks 5-8): Intensive Vision Therapy for Convergence and Accommodation Skills

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

1. Intensive Convergence Training:

·  Pencil Push-Ups with Accommodation Rock: The patient will perform pencil push-ups combined with accommodation rock exercises to improve convergence ability and accommodation skills simultaneously.

·  Brock String with Accommodative Targets:Advanced Brock string exercises will incorporate accommodative targets to challenge both convergence and accommodation systems.

2. Accommodative Facility Enhancement:

·  Flipper Lenses: Accommodative flipper lenses will be used to improve accommodative facility by gradually increasing the demand for near focus.

·  Near/Far Hart Chart Reading: Reading exercises using near and far Hart charts will be employed to enhance accommodative flexibility and accuracy.

Phase 3 (Weeks 9-12): Advanced Binocular Vision Exercises for Enhanced Stereopsis

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 stereopsis and overall binocular vision function.

1. Advanced Binocular Vision Exercises:

·  Random Dot Stereograms: The patient will engage in stereogram viewing exercises to improve stereopsis and depth perception.

·  Vectograms and Fusion Lock: Advanced fusion exercises using vectograms and fusion lock techniques will be employed to enhance binocular coordination.

2. Continued Monitoring and Refinement:

·  Regular Progress Assessments: Regular assessments of accommodation, vergence, and binocular vision parameters will continue to track progress and make necessary adjustments to the treatment plan.

·  Refinement of Techniques: Therapeutic techniques will be refined and customized based on the patient's response and individual needs to maximize treatment efficacy.

·  By dividing the treatment process into these three phases, we can systematically address specific aspects of the patient's binocular vision dysfunction and progressively work towards improving overall binocular vision function and symptom relief.

Discussion: 

Convergence insufficiency (CI) is a common binocular vision disorder that affects the ability to maintain proper eye alignment during near tasks, leading to symptoms such as eyestrain, diplopia, and difficulty focusing. This case report highlights the effectiveness of a structured 12-week vision therapy program in improving binocular vision function, including convergence, accommodation, fusional vergence, and stereopsis. The patient demonstrated significant improvements in all measured parameters, underscoring the importance of early diagnosis and tailored vision therapy in managing CI and related binocular vision dysfunctions.

Pre & Post Treatment Findings:

Table 1