Corresponding author at: Department of Medicine and Surgery, University of Salerno, Via Salvador Allende, 84081 Baronissi (SA), Italy. E-mail address: mdebernardo@unisa.it (M. De Bernardo). https://doi.org/10.1016/j.optom.2017.10.001 1888-4296/ © 2017 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. This is an open access article under the CC BY-NC-ND license (http://c...