Intervention and Outcomes
DRY EYE
Enrolled participants were randomized to receive either ATs containing 0.5% CMC (Refresh Plus; Allergan Inc., Dublin, Ireland) or control ATs containing 0.4% PEG (Systane PF; Alcon Labs, Fort Worth, TX, USA). For the purposes of masking, one researcher with no participant contact (Li, Y.) created 80 identical boxes, each labeled with a unique alphanumeric code. Boxes contained 30 similar, unlabeled, and transparent vials of either CMC (n = 40) or PEG (n = 40) ATs. Each alphanumeric code and its contents were recorded on a spreadsheet (Excel 2016; Microsoft, Redmond, WA, USA) and randomly paired with a numerical code (1–80) using a computer algorithm. Required sample size was calculated by power estimates in IBM SPSS 28 (IBM Corp., Armonk, NY, USA) with anticipated 20% participant dropout. The spreadsheet with listed interventions was not accessible to other researchers until completion of the protocol. Enrolled participants received boxes 1 to 80 in order of enrollment and used the alphanumeric box codes for identification. Participants were asked to instill one drop of the given AT in both eyes three times daily for seven days, spaced evenly throughout the day, and to return for follow-up on the seventh day. PEG-ATs were chosen as the control because of their similar physical properties and vial appearance, because saline solution has a noticeably lower viscosity than CMC-ATs.Primary outcomes included alpha diversity, beta diversity, and relative abundance of bacterial genera derived from pooled conjunctival swabs at days 1 and 7 for each participant. Secondary outcomes included the OSDI survey and compliance scores, collected from a computerized survey. Compliance scores were self-reported by participants as the estimated number of AT drops used in each eye daily, with ideal scores at one drops per eye daily although participants may have used more or fewer drops. The OSDI is a validated survey for assessing subjective dry eye symptomatology and quality of life, ranging from a score of 0 indicating no symptoms up to 48 indicating severe symptoms.