Potential Role of Ocular Surface Microbiome in Dry Eye: Microbial Interactions and Symptom Alleviation

Study design and sample collection This study is randomized, double-blind, and prospective trial. The inclusion criteria were as follows: patients aged 19 years or older with symptoms of dry eye syndrome. A total of 50 participants were randomly assigned to either the CsA group (n = 25, cyclosporine A twice a day and hyaluronic acid twice daily) or the control group (n = 25, hyaluronic acid four times daily). 0.05% cyclosporine A (Cyporin N Eye Drops, Taejoon Pharm, Republic of Korea) and 0.15% hyaluronic acid (New Hyaluni Eye Drops, Taejoon Pharm) were used in this study. Blinding was maintained by separating the examiner and the sample collector. Exclusion criteria included the use of topical ocular drops or systemic medication (such as systemic steroids, immunomodulators, and tetracyclines) that could influence study outcomes, as well as the presence of conjunctivitis, anterior blepharitis, Demodex infestation, parasitic eye infections, unresolved ocular trauma, healing disorders of the ocular surface (OS), a history of penetrating keratoplasty, contact lens use, or any ophthalmic surgical procedure within three months before baseline. Additionally, subjects with a single functional eye, pregnant or breastfeeding women, and those at risk of pregnancy without contraception were excluded. Clinical data and OS samples were collected at baseline before eye drop administration (V1) and at 4 weeks (V2) and 12 weeks (V3) after treatment initiation (Fig. 1a). Of the 50 participants at V1, 21 participants from each group completed follow-up at V2, while 14 participants in the CsA group and 18 participants in the Newhyaluni group remained at V3. OS samples for microbiome analysis were obtained from the inferior conjunctival sac using sterile mixed cellulose ester (MCF) membrane (Millipore, Merck). OS samples were collected from 13 participants in the CsA group and 13 participants in the Newhyaluni group. All OS samples were stored at -80 °C until DNA extraction for micro