Near Vergence Training for Distance Control in Intermittent Exotropia

Inclusion criteria

• 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.

Exclusion criteria

• 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).