The Closed Eye Harbors a Distinct Microbiome in Dry Eye Disease: A Randomized Clinical Trial of the Efficacy of a Saline Rinse Upon Awakening

Abstract

Purpose : Neutrophils are known to populate closed eye tears, potentially as a response to entrapped microbiota. This study sought to characterize the closed eye microbiome over the course of a therapeutic trial testing the effectiveness of an eye wash upon awakening as a therapy for dry eye disease.

Methods : A prospective clinical trial involving 36 normal and 36 dry eye subjects was conducted, and subjects were randomized to perform daily eye washes with phosphate buffered saline at awakening for one month, or for once every two weeks. Aliquots were taken from tear washes at baseline and after one month of eye washes upon awakening. Illumina MiSeq metabarcoding was performed using the microbial 16S rRNA gene. After removing any samples with < 1000 reads and any sequences aligned to Chloroplasts or Cyanobacteria, the relative abundance was normalized using a log₂ transformation of cumulative-sum scaling. Microbial community composition alpha diversity was characterized using the evenness, richness and Shannon indices and beta diversity was examined using principal coordinates analysis (PCoA), redundancy analysis (RDA) and canonical correspondence analysis (CCA). Differences in beta diversity were quantified using PERMANOVA with 999 permutations of Bray-Curtis dissimilarity and relative abundance using ANOVA adjusted for false discovery. Spearman correlation network analysis was used to examine microbial community interrelatedness.

Results : The closed eye microbiome of the dry eye is different from randomized controls. The alpha diversity of the dry eye is increased (richness ANOVA f =4.8 p =7.5 x10^-5, evenness ANOVA f =13 p =2.1x10^-12, Shannon ANOVA f = 12 p =5.9 x10^-12) and the beta diversity differs (PCoA PERMANOVA R² =0.21 p =0.00033, RDA variance =95.25 f =3.71 p =0.001, CCA chi² =0.16 f =3.64 p =0.001) between individuals with dry eye as compared to controls without dry eye. The closed eye microbiome does not significantly change with daily eye wash (PERMANOVA R² =0.0156 P =0.271).

Conclusions : The closed microbiome of the dry eye is distinct from controls and remains distinct despite a month of daily non-pharmacologic wash.

This is a 2020 ARVO Annual Meeting abstract.

 

Fig. 1. Patients with dry eye have a different microbiome. (a) Alpha diversity. (b) Beta Diversity. (c) Relative abundance. (d) Spearman network analysis.