To determine whether the time of day at which daily occlusion (patching) is administered - morning (08:00-10:00) versus evening (17:00-19:00) - affects the amount of visual-acuity improvement in the amblyopic eye in children with unilateral amblyopia.

Rationale:

While occlusion therapy remains the mainstay for treatment of childhood amblyopia, existing trials have focused on patching duration, not on the timing of occlusion. Diurnal or chronobiological factors - such as fluctuations in neuroplasticity, attention, compliance, or visual demand during the day - may influence the efficacy of patching. Understanding whether timing matters could help optimize occlusion therapy, improve outcomes, and reduce treatment burden.

Study Type: Prospective, randomized, parallel-group clinical trial.

Participants: Children aged 4-8 years with unilateral amblyopia; amblyopic-eye BCVA between 0.17-0.67 decimal (≈ 6/36-6/9); fellow-eye BCVA ≥ 0.80 decimal; refractive-dominant or strabismic/mixed amblyopia. Parental/guardian consent required.

Randomization & Stratification: Participants randomized 1:1 to "Morning patching" vs "Evening patching" arms. Stratified by age (4-<6 vs >=6-8), baseline visual acuity or amblyopia severity (moderate 6/36-<6/12 vs mild 6/12-6/9), and amblyopia type (refractive-dominant vs strabismic/mixed) - to ensure balance across key prognostic variables.

Intervention: Daily occlusion of the non-amblyopic eye for 2 continuous hours, at assigned time window (Morning: 08:00-10:00; Evening: 17:00-19:00). During patching, child engages in near-vision tasks (reading, puzzles, coloring) for 20-30 min or more. Adherence monitored via parent diary/photos. Spectacle correction (if prescribed) maintained throughout.

Follow-up / Assessments:

Baseline exam (BCVA both eyes, refraction, ocular alignment/strabismus assessment, anterior and posterior segment exam, stereoacuity, instructions on patching/adherence, randomization).

Midpoint follow-up at 3 months (BCVA, adherence, adverse events. Telehealth acceptable if in-person not possible.).

Final follow-up at 6 months (BCVA (primary endpoint), stereoacuity, ocular alignment/strabismus assessment, anterior segment exam, adherence data review, adverse events, patching compliance summary.).

Primary Outcome: Change in best-corrected visual acuity (BCVA) of the amblyopic eye from baseline to month 6.

Secondary Outcomes: Stereoacuity improvement, adherence rate (% of days/patching sessions completed).

Statistical Approach: Analysis of covariance (ANCOVA) comparing mean change in BCVA between arms, adjusting for baseline VA and stratification factors. Subgroup analyses by amblyopia type, baseline severity, age group.

Sample Size / Power (Summary):

Target total enrollment ~100 children (≈ 50 per arm), to provide sufficient power to detect a clinically meaningful difference (≈ 1 line difference in BCVA) between morning and evening patching, while allowing for variability, drop-outs, and stratified analyses.

Duration & Timeline:

Each participant will be followed for 6 months of daily patching. The total study duration (from first enrollment to last follow-up) will depend on recruitment rate; estimated duration ~ 7-9 months including recruitment, follow-up, data cleaning, and analysis.

Significance & Expected Impact:

If timing of occlusion influences visual outcome, this could refine occlusion therapy recommendations - potentially improving efficacy, adherence, and convenience for patients and families. The trial may identify a more effective or practical patching schedule, thereby contributing to evidence-based amblyopia management.

Inclusion Criteria:

• Age: 4-8 years.
• Unilateral amblyopia.
• Amblyopic-eye BCVA decimal 0.17-0.67 (≈ 6/36-6/9).
• Fellow-eye BCVA ≥ 0.80 decimal (≈ 6/7.5 or better).
• Amblyopia type: refractive-dominant or strabismic/mixed.
• Parent/guardian consent obtained.

Exclusion Criteria:

• Bilateral amblyopia.
• Sensory-deprivation amblyopia (e.g., due to congenital cataract, ptosis, corneal opacity).
• Ocular surgery within the past 6 months, or planned surgery during study.
• Likely poor adherence (e.g., due to social, logistic, or family constraints).

Outcome assessments (visual acuity, stereoacuity, ocular alignment) will be performed by trained examiners (e.g., optometrists/orthoptists) who are not involved in randomization, patching-instructions, or adherence monitoring, and who will remain masked to the child's assignment (morning vs evening patching). Allocation will be concealed via a central computer-generated randomization list; the enrolling investigator will not communicate assignment to the assessor. Standard operating procedures (chart, lighting, refractive correction, instructions) will be used uniformly. Data entered in the database will use non-descriptive group codes ("Group A" / "Group B"), and the statistician will remain blinded until the database is locked and primary analysis is complete.