The Effectiveness of Visual Training in Convergence Insufficiency Patients

The Effectiveness of Visual Training Using Prisms on Visual Symptoms and Binocular Vision in Convergence Insufficiency Patients

Convergence insufficiency (CI) is one of the most common binocular vision disorders. The prevalence of CI ranges from 3% to 6% in school-aged children. CI symptoms include visual fatigue, headache, blurred vision, and diplopia and could be caused while using near-distance viewing. These symptoms might become more severe with increasing need to perform near-distance tasks. Long-term visual symptoms could result in a negative impact on learning behaviors and work performance in patients. Nowadays, visual training is the main type of management for CI patients clinically; however, the existing training protocol required patients to make several visits to the clinic for visual training, which might increase the burden for patients and result in higher failures in training. Therefore, this study will use a simple training method by utilizing prisms for CI patients to train at home, then compare visual symptoms and binocular vision after the training. In stage I of this study, investigators will recruit 60 symptomatic CI participants aged 9 to 30 years old to do a 6-week visual training with the prisms (15 min/time, 3 times/week). The post-training outcomes will be collected at week 4 and week 6. In stage II, all of the participants will be randomly divided into the "stop training group" and the "continue training group." The participants in the "continue training group" will have the same 6-week prism training and in the "stop training group" will stop all the prism training during this period. The final post-training outcomes of all the participants will be collected again at week 12. In this study, investigators will investigate the effectiveness of the prisms training for 6 weeks and for 12 weeks on visual symptoms and binocular vision in CI patients, and evaluate whether the training effect will be affected by stopping training after 6 weeks.

Study Overview

• Status: Completed
• Conditions: Convergence Insufficiency
• Intervention / Treatment: Behavioral: Visual training

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Taiwan
  • Taipei county, Taiwan, 100225
    • National Taiwan University Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 5 years to 26 years (Child, Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. The overall score of CI symptom survey ≥ 16 (9-18 years old) or ≥ 21 (19-30 years old)
2. The break point of near point of convergence (NPC) ≥ 6 cm
3. Exophoria at near distances be at least 4∆ higher than at far distances
4. Near positive fusional vergence (PFV) ≤ 15∆ or failing Sheard's criterion at near.

Exclusion Criteria:

1. The best corrected visual acuity (BCVA) of < 20/25 in each eye at far and near distances
2. Amblyopia patients or the difference of BCVA between the two eyes ≥ 2 lines
3. Constant strabismus patients
4. History of strabismus surgery or refractive surgery
5. Systemic diseases that would affect binocular vision
6. Acquired brain injury or neurological disorder.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Health Services Research
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Stop training group; Home-base prism training during week 1-6 --> then stop training during week 7-12 --> endpoint data collected at week 12	Behavioral: Visual training; Visual training is the main type of management for CI patients clinically; however, the existing training protocol required patients to make several visits to the clinic for visual training, which might increase the burden for patients and result in higher failures in training. Therefore, this study will use a simple training method by utilizing prisms for CI patients to train at home, then compare visual symptoms and binocular vision after the training.
Experimental: Continune training group; Home-base prism training during week 1-12 --> endpoint data collected at week 12	Behavioral: Visual training; Visual training is the main type of management for CI patients clinically; however, the existing training protocol required patients to make several visits to the clinic for visual training, which might increase the burden for patients and result in higher failures in training. Therefore, this study will use a simple training method by utilizing prisms for CI patients to train at home, then compare visual symptoms and binocular vision after the training.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Binocular vision and visual function evaluation	Change from baseline best corrected visual acuity: distance visual acuity measured for each eye at a distance of 6 m and at near 40 cm for each eye will be measured using Snellen charts. NPC and the amplitude of accommodation will be measured using Royal Air Force (RAF) rule. Stereoacuity will be measured by the Random dot stereotest.	12 weeks for each participant

Collaborators and Investigators

• Sponsor: National Taiwan University Hospital
• Investigators: Principal Investigator: Tzu-Hsun Tsai, PhD, National Taiwan University Hospital

Study record dates

Study Major Dates

• Study Start (Actual): March 6, 2023
• Primary Completion (Actual): June 26, 2024
• Study Completion (Actual): June 26, 2024

Study Registration Dates

• First Submitted: October 25, 2022
• First Submitted That Met QC Criteria: November 2, 2022
• First Posted (Actual): November 3, 2022

Study Record Updates

• Last Update Posted (Actual): December 3, 2024
• Last Update Submitted That Met QC Criteria: November 28, 2024
• Last Verified: March 1, 2023

More Information

Terms related to this study

• Keywords: Visual training; Prism; Binocular vision
• Additional Relevant MeSH Terms: Central Nervous System Diseases; Nervous System Diseases; Eye Diseases; Cranial Nerve Diseases; Strabismus; Ocular Motility Disorders
• Other Study ID Numbers: 202207058RINB

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No