Randomization
After baseline measurements, participants will be randomly allocated (stratified by therapist) to either the intervention or control group, by means of computer-generated tables. Trained OTs employed by the participating low vision multidisciplinary rehabilitation institutions in the Netherlands and in Belgium will provide therapy for older adults with DSL and their communication partner (i.e. the intervention group) according to the newly developed DSL protocol. To prevent unequal distributions of participants in the control and intervention groups among OTs, participants will be stratified within working areas of OTs before randomization resulting in eight strata, one for each of the eight participating OTs (four OTs from Bartiméus, two OTs from Visio and two OTs from Blindenzorg Licht en Liefde). Block randomization will be performed in blocks of two to ensure equal group sizes in each stratum. Randomization will be performed by an independent researcher using a computer-generated allocation scheme so that the researcher who will analyze the data is blinded (trained research assistants will enter all data into a laptop computer using codes). All participants will be informed about the allocation. In case a participant is allocated to the treatment group, an email will be sent to inform the designated OT. Treatment will take place in the participant’s home in 3–5 appointments, depending on the individual needs of the participant and/or proxy. All participants have received low vision rehabilitation and hearing aid fitting before entering the study. Using a waiting list procedure, participants in the control group will be offered treatment after 3-month follow-up measurements.
invited to participate in the RCT. Hearing aid owners will be invited to participate because hearing aids, and making optimal use of hearing aids, are an important part of the DSL protocol. In addition, by selecting hearing aid owners with hearing problems by using information from the questionnaire, patients with both objective hearing loss (reimbursement of hearing aids from a hearing loss of at least 35 dB) and self-reported hearing disability will be selected; these patients are expected to be motivated and the most suitable for rehabilitation [48]. Moreover, due to time constraints, it is not possible to wait for patients to fit hearing aids in order to be able to take part in the trial; this procedure may take months due to the required testing period and possible reimbursement.
Written information will be sent to eligible patients and informed consent will be signed prior to inclusion. It is expected that about 1500 patients need to be screened to include 124 eligible participants in the trial. Patients who are unable to comprehend or respond to questions due to cognitive impairment, or have insufficient knowledge of the Dutch language, will be excluded from the study. Table 1 summarizes the inclusion/exclusion criteria.