[1] NOVA Univ Lisbon, Natl Sch Publ Hlth, Lisbon, Portugal
[2] NOVA Univ Lisbon, Natl Sch Publ Hlth, Publ Hlth Res Ctr, Lisbon, Portugal
[3] Linnaeus Univ Kalmar, Dept Med & Optometry, Kalmar, Sweden
[4] Univ Minho Braga, Low Vis & Visual Rehabil Lab, Dept & Ctr Phys Optometry & Vis Sci, Braga, Portugal
[5] UCL, Inst Ophthalmol, London, England
[6] Peking Univ, Natl Sch Dev, Beijing, Peoples R China