Effects of Carboxymethylcellulose Artificial Tears on the Eye Microbiome

Sampled 16S rRNA sequences were organized into 'operational taxonomic units' (OTUs) at a 97% sequence similarity threshold, and a phylogenetic tree was constructed from sampled OTUs using the QIIME2 bioinformatics platform. Faith's phylogenetic diversity was used as a measure of species richness, calculated as the sum of all phylogenetic tree branch lengths using the QIIME2 faith_pd plugin. The units for this measure are the number of nucleotide substitutions (phylogenetic distance, i.e. length) per branch, which is a scale measure from zero to infinity. Zero indicates a completely homogenous sample, and higher scores indicate greater species richness.

Sampled 16S rRNA sequences were organized into 'operational taxonomic units' (OTUs) at a 97% sequence similarity threshold. Shannon's diversity index was used as a measure of species diversity, calculated as the sum of -p/ln(p), where p is the proportion of the sample made up of each OTU using the QIIME2 shannon_pd plugin. This measure is a unitless scale proportion ranging from zero to infinity. Zero indicates a completely homogenous sample, and higher scores indicate greater species diversity.

Sampled 16S rRNA sequences were organized into 'operational taxonomic units' (OTUs) at a 97% sequence similarity threshold, and a phylogenetic tree was constructed from sampled OTUs using the QIIME2 bioinformatics platform. Unweighted UniFrac distances were calculated as the number of shared nucleotide substitutions between two samples divided by the number of shared nucleotide substitutions among all samples using the QIIME2 unifrac plugin. The unweighted UniFrac is a unitless scale proportion ranging from zero to one. Greater UniFrac distances indicate greater beta diversity.

Sampled 16S rRNA sequences were organized into 'operational taxonomic units' (OTUs) at a 97% sequence similarity threshold, and a phylogenetic tree was constructed from sampled OTUs using the QIIME2 bioinformatics platform. Weighted UniFrac distances were calculated as the number of shared nucleotide substitutions between two samples divided by the number of shared nucleotide substitutions among all samples using the QIIME2 unifrac plugin, with samples weighted by abundance of species. The weighted UniFrac (weighted by number of duplicate OTUs) is a unitless scale proportion ranging from zero to infinity. Greater UniFrac distances indicate greater beta diversity.

The Ocular Surface Disease Index (OSDI) is a 12-item scale for the assessment of symptoms related to dry eye disease and their effect on vision. Participants conducted a survey before and after intervention, and the difference will be used as the outcome measure. The OSDI ranges from 0 to 48, and a higher score indicates greater ocular surface dryness. If reporting the difference, a more negative change in OSDI indicates greater improvement in dry eye symptoms. Pairwise Wilcoxon signed rank tests were used to compare changes in OSDI between intervention groups at a two-tailed 95% confidence interval.

Patients will be asked 1 week after intervention how many times they administered eye drops each day. This measures compliance with intervention, ranging from zero drops per day to infinite drops per day. If a patient is perfectly compliant, the number of drops should be 3. Mann-U-Whitney tests were used to compare compliance between intervention groups at a two-tailed 95% confidence interval.