After participant allocation, telephonic follow up will be made during both periods of the trial with a frequency that is dependent on the intervention group of the patient in that period. Participants in the HBE group will be called weekly for 2 weeks, and then will be called biweekly for a month, until each period of 6 weeks has ended. In contrast, patients in the control group will be called every three weeks along each period. With the purpose of verifying both HBE adherence and correct use of wooden prisms, every participant will be asked to send a photograph of the bed head legs during the follow-up telephone call. The photograph will be received by the researcher via e-mail or smart-phone and will be encoded and saved in a hard disk. At the end of the first period, RDQ and SF-36 questionnaires will be applied and researchers will store the returned prisms during washout period. When washout period has ended, RDQ and SF-36 questionnaires will be applied again in order to be sure of the absence of any carry-over effect in the group initially allocated to HBE. Finally at week 14, RDQ, SF-36 and Patient Preference questionnaires will be administered to complete study ending outcome assessments.