Washed Microbiota Transplantation for Dry Eye Disease: A Hypothesis-Generating Observation
Background: Dry eye disease (DED) is a multifactorial ocular surface disorder characterized by a loss of tear film homeostasis. The "Gut-Eye Axis" reveals that the gut microbiome can influence the eye by modulating systemic immune and inflammatory status. We report a case of DED treated with washed microbiota transplantation (WMT) and describe the associated clinical and microbiological observations.Case Presentation: A 52-year-old male who suffered from chronic urticaria and evaporative DED was treated with three courses of WMT. Another 59-year-old male with evaporative DED was treated with preservative-free topical artificial tears as a reference case. Clinical parameters, including the Ocular Surface Disease Index (OSDI), Schirmer test I, non-invasive average break-up time (NIABUT), and tear meniscus height (TMH) and meibomian gland evaluations were evaluated in both patients before and after therapies. Conjunctival swabs and fecal samples from the index case, and conjunctival swabs from the reference case, were collected pre- and post-therapy for 16S rRNA gene sequencing. The patient receiving WMT showed marked clinical improvement, evidenced by increased TMH and NIABUT, and a decreased OSDI score. Changes were observed in the composition of both the ocular surface and gut microbiota of the index case after WMT. At the genus level, bacteria such as Bacteroides and Prevotella increased in relative abundance. Concurrently, the relative abundance of the phylum Firmicutes decreased in both ocular and gut microbiota. The reference case treated with topical artificial tears exhibited clinical improvements in Schirmer test I, TMH and NIABUT; however, no significant changes were observed in the ocular surface microbiota.Conclusions: This case study generates the hypothesis that WMT may exert therapeutic effects in evaporative DED, possibly through systemic immunomodulation and microbiota remodeling. These observations warrant further investigation in controlled studies.