Near Vergence Training for Distance Control in Intermittent Exotropia

NCT07642687 | Recruiting

• 1 other identifier: HSEARS20251213004
• Study Type: interventional
• Target: 42
• Locations: 1 country
• Sites: 1

Brief Summary

Intermittent Exotropia (IXT) is a common type of eye misalignment where one eye periodically turns outward, and control is typically much worse when looking at objects far away than close up. However, most currently available training programme are focused on near-viewing tasks. The goal of this clinical trial is to investigate if a new, structured, home-based near eye training program works to improve distance eye alignment control in children and young adults with IXT. The main questions the study aims to answer are:

• Does a 12-week near eye training program improve a participant's ability to control their eye alignment when looking at a distance?
• Does using a special reading glasses during near training help to control distance eye alignment better than doing the training without the reading glasses?
• Do the benefits of this eye training last after the training has stopped? This is a two- phase, single- masked (examiner masked), randomized clinical trial with crossover design. The entire study duration is about 24 weeks. A total sample size of 42 participants, aged 6 to 25 years with diagnosed Basic (distance deviation is within 10 prism diopters of the near deviation) or Divergence excess (distance deviation is at least 10 prism diopters greater than the near deviation) IXT, will be recruited. In Phase I (Weeks 0 to 12), participants will be randomly allocated into one of three groups, with 14 individuals in each group:
• Group 1 does eye training while wearing special plus-power reading glasses that remove the need to focus up close, mimicking how the eyes look at a distance.
• Group 2 does the exact same eye training but wears regular distance glasses without the special reading addition.
• Group 3 serves as a control group that does not do training during the first 12 weeks, but will receive the training in the second phase. In Phase II (Weeks 13 to 24), which is a crossover phase, groups 1 and 2 will stop training to see if the visual improvements last, while group 3 will be re-randomized into two subgroups (group 3A, with special plus-power reading glasses, and group 3B with regular glasses with distance correction) that will undertake daily eye training for 12 weeks to ensure ethical treatment access. All participants will have a final eye exam at 24 weeks. During home training, participants will:
• Wear standard glasses provided by the study.
• Practice daily, home-based eye exercises for 12 weeks using a standardized software program on a computer or tablet.
• Complete 3 training sessions every day, lasting 7 minutes per session.
• Wear red-blue 3D glasses during training and press arrow keys or swipe the screen to play a visual game that dynamically changes in difficulty. Preliminary test and binocular vision assessment with fixed and uniform sequence will be performed at baseline visit, 6th week interim visit, 12th and 24th week evaluation. All eye examinations will be carried out in The Optometry Centre (A034), the School of Optometry, The Hong Kong Polytechnic University. The following data will be statistically analyzed. The primary outcome data is distance Office Control Score (OCS) at 12-week visit. Secondary outcomes data include change in deviation angle, near and distance stereopsis and patient- / parent- reported health-related quality-of-life questions at 12-week.

Conditions

Intermittent Exotropia

Outcome Measures

Primary Outcomes (1)

• Change of Distance Office Control Score

  Objective and quantitative office control scale, based on the frequency of deviation and the recovery speed followed by occlusion. Ranged from 0 to 5, with score 0 represents the best control (phoria with excellent control), and score 5 represents the worst control (constant exotropia during the 30-second observation)

  Baseline, 6-week, 12-week and 24-week

Secondary Outcomes (5)

• Change of exodeviation magnitude angle

  Baseline, 6-week, 12-week and 24-week

• Change of Distance stereoacuity

  Baseline, 6-week, 12-week and 24-week

• Change of Near stereoacuity

  Baseline, 6-week, 12-week and 24-week

• Change of Quality of Life (QoL) measures - Chinese Intermittent Exotropia Questionnaire (CIXTQ) for children aged 5 to 17 and parents of children aged 2 to 17

  Baseline, 12-week and 24-week

• Change of Quality of Life (QoL) measures - The Chinese Adult Strabismus Quality of Life Questionnaire (CAS-20) for adult participants aged 18 or above

  Baseline, 12-week and 24-week

Study Arms (3)

Active training group with reading glasses

ACTIVE COMPARATOR

Receiving training in Phase I (Weeks 0 to 12), stop training in Phase II (Weeks 13 to 24) to study the effect persistence

Other: Home-based near eye training program

Active training group without reading glasses

ACTIVE COMPARATOR

Receiving training in Phase I (Weeks 0 to 12), stop training in Phase II (Weeks 13 to 24) to study the effect persistence

Other: Home-based near eye training program

Control group

NO INTERVENTION

No training will be received in Phase I (Weeks 0 to 12); Will receive training in Phase II of the study (Weeks 13 to 24) to ensure ethical treatment access

Interventions

Home-based near eye training program OTHER

Standardized home-based near vergence training platform with data visualization tools and communication platforms

Active training group with reading glasses; Active training group without reading glasses

Eligibility Criteria

• Age: 6 Years - 25 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• Age and Diagnosis: Participants must be aged 6 to ≤ 25 years at the time of screening, with a confirmed clinical diagnosis of either Basic or Divergence Excess (DE) Intermittent Exotropia (IXT).
• Ocular Alignment Magnitude: Distance exodeviation measuring between 10 and 40 prism diopters (pd) inclusive, determined by the prism and alternate cover test (PACT).
• Distance-Near Disparity Limits: Near exodeviation must not exceed the distance exodeviation by more than 10 pd (to exclude Convergence Insufficiency type exotropia).
• Baseline Distance Control: A baseline distance IXT Office Control Score (OCS) between Grade 2 and Grade 4 inclusive, based on the mean of 3 standardized assessments.
• Baseline Near Control: A baseline near IXT control score less than or equal to the distance IXT control score, based on the mean of 3 standardized assessments.
• Visual Acuity: Best-corrected visual acuity (BCVA) of Logarithm of the Minimum Angle of Resolution (logMAR) 0.1 or better in each eye at both distance and near fixation.
• Sensory Status: Measurable near stereoacuity of 400 arc seconds or better on the Preschool Randot stereoacuity test.
• Refractive Correction Stability: Compliance with wearing a stable, appropriate spectacle correction for ≥ 4 months prior to formal baseline assessment if the participant meets any of the following refractive thresholds:
• Myopia \< -0.50D spherical equivalent (SE) in either eye.
• Hyperopia \> +2.50D SE in either eye.
• Anisometropia \> 1.00 SE.
• Astigmatism \> 1.50D cylinder in either eye.
• Treatment History: No history of prior non-surgical interventions for IXT, including patching, vision therapy/orthoptics, or overminus lens therapy (≥ 0.50 D).
• Surgical History: No prior history of strabismus surgery, extraocular muscle botulinum toxin injections, intraocular surgery, or refractive surgery.
• Trial Commitment: No planned strabismus surgery or conflicting ocular therapies during the 24-week study period.

You may not qualify if:

• Amblyopia and Co-morbid Strabismus: Presence of amblyopia, nystagmus, restrictive strabismus, or paretic strabismus.
• Vertical Misalignment: Presence of an associated vertical ocular deviation \> 5 pd.
• Significant Pathologies: Co-existing significant ocular disease or neurological disorders (e.g., cerebral palsy) that could confound oculomotor or sensory evaluations.
• Confounding Medications: Regular use of systemic or topical ocular medications known to alter accommodative or vergence function within the 3 months prior to screening (including, but not limited to, atropine, pirenzepine, or systemic anti-epileptic agents).

Sponsors & Collaborators

• The Hong Kong Polytechnic University: lead

Study Sites (1)

The Optometry Clinic, The Hong Kong Polytechnic University

Hong Kong, Hong Kong

RECRUITING

Related Publications (2)

• Mohney BG, Holmes JM. An office-based scale for assessing control in intermittent exotropia. Strabismus. 2006 Sep;14(3):147-50. doi: 10.1080/09273970600894716.

  PMID: 16950743 BACKGROUND

• Ma MM, Kang Y, Scheiman M, Chen Q, Ye X, Pan L, Deng J, Su G, Zhang G, Chen X. Office-based vergence and anti-suppression therapy for the treatment of small-to-moderate angle intermittent exotropia: A randomised clinical trial. Ophthalmic Physiol Opt. 2024 Mar;44(2):356-377. doi: 10.1111/opo.13264. Epub 2023 Dec 26.

  PMID: 38146812 BACKGROUND

Central Study Contacts

Horace Ho-yin Wong, MClinOptom, BSc (Hons) Optom

CONTACT

852-63384048; horace.wong@polyu.edu.hk

Tsz Wing Leung, PhD

CONTACT

852- 27664268; jeffrey.TW.leung@polyu.edu.hk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Study Record Dates

• First Submitted: June 3, 2026
• First Posted: June 11, 2026
• Study Start: June 1, 2026
• Primary Completion (Estimated): June 1, 2028
• Study Completion (Estimated): December 1, 2028
• Last Updated: June 11, 2026

Record last verified: 2026-05

Locations

HK (1)