This clinical study investigates whether watching 3D films can help improve the vision of children with residual amblyopia (lazy eye), that is, those children who, despite having undergone usual treatments such as glasses or patching, still maintain some visual deficit. The main objective is to verify whether viewing in 3D is better than viewing in 2D in improving depth vision (stereopsis), visual acuity and ocular alignment. The hypothesis is that 3D films, by providing richer binocular stimuli, will produce greater improvements than the same 2D films.

Children between 4 and 14 years of age with residual, stable and previously treated unilateral amblyopia will be included. Participants will be recruited from the pediatric ophthalmology/optometry clinics of the Mútua University Hospital

The study will be conducted in two locations: the visual examinations will be performed at the Mútua University Hospital in Terrassa, and the film sessions at the Faculty of Optics and Optometry of Terrassa (FOOT, UPC), in rooms prepared with a projector and 3D glasses.

The design is randomized and controlled. In a first phase, the children will be randomly divided into two groups: one group will watch 3 films in 3D and the other will watch the same films in 2D. Then, in a second phase, all participants will watch 3 additional sessions in 3D. Four evaluation visits will be made: before starting, after phase 1, after phase 2 and a follow-up two months later. These visits will measure stereopsis, visual acuity, and ocular deviation with standard optometric tests.

Watching 3D movies is a safe and non-invasive activity; therefore, no significant risks are expected beyond some possible mild and transient discomfort such as eye strain or headache, which will be recorded if it occurs. Potential benefits include improved depth perception and other visual functions, and the results could open the door to new, fun and motivating therapeutic options for other children with amblyopia in the future.

Inclusion Criteria:

• Children aged 4 to 12 years.
• Previous diagnosis of unilateral amblyopia (anisometropic, strabismic, or mixed).
• History of conventional treatment (optical correction, occlusion and/or penalization) with stable visual acuity for at least 6 months.
• Interocular visual acuity difference ≥ 0.2 logMAR (≈ ≥2 Snellen lines).
• Ability to understand and follow age-appropriate basic instructions.
• Parent/guardian consent (and child assent when applicable)

Exclusion Criteria:

• Ocular surgery within the last 6 months.
• Manifest strabismus >15 prism diopters.
• Concomitant ocular pathology that may affect vision (e.g., cataract, nystagmus, ptosis, corneal opacity, retinal disease, optic neuropathy).
• Cognitive or neurological deficits preventing compliance with the protocol.
• Prior intensive exposure to 3D cinema or VR/3D videogames that could act as a confounder.
• Family or child refusal to participate