Literature on the benefits of screening and treatment of amblyopia emphasizes the costs of insufficiently treated amblyopic patients who lose their better eye. However, patients with insufficiently treated amblyopia and strabismus who do not lose their better eye only experience a slight decrease in their quality of life, and such patients occur more frequently. We designed and validated a questionnaire for amblyopia and strabismus in order to assess the decrease in quality of life of such patients. Complaints were collected from outpatients and reduced to five domains, pertaining to distance estimation, visual disorientation, problems with social contacts and cosmetic problems, diplopia, and fear of losing the better eye. For these domains 26 questions were formulated that constitute the Amblyopia & Strabismus Questionnaire (A&SQ). The A&SQ, the National Eye Institute Visual Function Questionnaire-25 (VFQ-25) and the Short Form-12 Health Survey (SF-12) were presented to 53 healthy controls, 68 outpatients and a cohort of 174 outpatients born between 1962 and 1972 and treated between 1968 and 1974 for amblyopia and strabismus. The quality of life was best in healthy controls and worst in current outpatients, not only on the SF-12 and the VFQ-25 but also on the A&SQ, demonstrating an acceptable construct validity of the A&SQ. The decrease in the quality of life as measured by the A&SQ was most outspoken in our outpatient group of amblyopia and strabismus patients, less in the cohort that had been treated 30 years previously and least in the healthy controls, demonstrating an acceptable discriminatory validity of the A&SQ.