1. From the Health Economics and Decision Science, University of Sheffield, Sheffield, United Kingdom; the2Catalan Agency for Health Technology Assessment and Research, Catalan Health Service, Catalan, Spain; and the
2. From the Health Economics and Decision Science, University of Sheffield, Sheffield, United Kingdom; the
3. Departments of Orthoptics and
4. Ophthalmology, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom.