Principal Findings
In this randomized factorial design study, we compared the effectiveness of the use of phone call, mailed letter, as well as mail and phone call combined for engaging patients into booking an appointment for a primary care practice embedded with a teleophthalmology program. We found that calling patients was much more effective than sending a letter; we also found that sending a letter ahead of the phone call did not further increase the likelihood of booking an appointment.Although no studies have examined the effectiveness of these patient engagement approaches in the context of a teleophthalmology program, many have examined their effectiveness in the context of regular in-person screening programs for DR. Our findings are consistent with previous studies examining improving engagement in DR screening, showing that phoning patients is more effective than mailing out letters [