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Ocular Surface Microbiome in Dry Eye Patients

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ClinicalTrials.gov Identifier: NCT02161341
Recruitment Status : Completed
First Posted : June 11, 2014
Last Update Posted : October 31, 2018
Information provided by (Responsible Party):
Louis Tong, Singapore National Eye Centre

Brief Summary:
The ocular surface is the first line of defence of the eye, it is therefore where external threats are sensed, and potential insults neutralised. Over the course of evolution, various microbes, especially bacteriae, have come to colonise the ocular surface as commensals. The commensals have a role to maintain the homeostasis of the ocular surface. 1 The innate immunity of the ocular surface is very active, and consists of active mechanisms to suppress inflammation 2. For example, there exist macrophages, dendritic cells, suppressor cells, regulatory cells, B cells, IgA, lysozyme, anti-microbial peptides and barriers against external agents. The normal commensals of the ocular surface maintain a basal level of activation of innate defence by stimulating the pattern recognition receptors on ocular surface epithelial cells. This normal composition of microbes is important since inflammation and infection will result if there is introduction of a pathogenic strain that overcomes the flora, or if a dominant strain secretes excessively immunogenic products, such as the exotoxin A of Staphylococcus which triggers marginal keratitis, a form of type IV hypersensitivity. The flora load of microbiome could also influence tear function as a higher flora load was found to be associated with increased mucin degradation 3 and reduced globet cell densitiy 4. Previous studies [I'm not sure which studies these are] at SERI/SNEC also point to the importance of microbes. For example, in dry eye patients, there is increased lysophospholipids in the tear, and this may contribute to inflammatory mediators such as arachidonic acid and other metabolites. The lysophospholipids are formed by phospholipase A2 reactions, and the latter may be microbial in origin. Since dry eye is a known inflammatory disease of the ocular surface, this is one way that microbes can contribute to the pathology.

Condition or disease
Dry Eye

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Study Type : Observational
Actual Enrollment : 82 participants
Observational Model: Case-Control
Time Perspective: Cross-Sectional
Official Title: Exploratory Study on the Ocular Surface Microbiome and Correlation to Clinical Parameters
Study Start Date : June 2014
Actual Primary Completion Date : October 2018
Actual Study Completion Date : October 2018

Primary Outcome Measures :
  1. bacterial microbiome [ Time Frame: 1 day ]
    Determine the composition of the bacterial microbiome of the human ocular surface in normal volunteers and dry eye patients

Secondary Outcome Measures :
  1. Gene expression [ Time Frame: 1 day ]
    Determine the bacterial gene expression (bacterial transcripts) found in the human ocular surface.

  2. Clinical characteristic [ Time Frame: 1 day ]
    Characterise any feature of the microbiome that may be linked to clinical characteristics such as age, status of tearfilm, Meibomian gland dysfunction, exposure to environmental stimulation such as smoking, etc

Biospecimen Retention:   Samples Without DNA
Microbiome swab will be collected from the inferior fornix of the lower eyelids to determine composition of the bacterial microbiome of the human ocular surface in normal volunteers and dry eye patients

Information from the National Library of Medicine

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Ages Eligible for Study:   21 Years to 85 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Sampling Method:   Non-Probability Sample
Study Population
Dry eye patients and healthy normal volunteers

Inclusion Criteria:

  • Subjects must be 21 years or older
  • Willing to perform all the eye examinations in this study

Exclusion Criteria:

  • Known history of thyroid disorders (diagnosed by physician).
  • Known history of Sjogren syndrome or rheumatoid arthritis (diagnosed by physician).
  • No ocular surgery within the last 3 months and LASIK within 1 year.
  • Ocular surface diseases such as pterygium, or obvious lid/orbital disease with lagophthalmos.
  • Any other specified reason as determined by clinical investigator.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02161341

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Singapore Eye Research Institute
Singapore, Singapore, 168751
Sponsors and Collaborators
Singapore National Eye Centre
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Responsible Party: Louis Tong, Clinician-Scientist, Senior Consultant, Singapore National Eye Centre
ClinicalTrials.gov Identifier: NCT02161341    
Other Study ID Numbers: R1146/48/2014
2014/520/A ( Other Identifier: SingHealth Centralised Institutional Review Board )
First Posted: June 11, 2014    Key Record Dates
Last Update Posted: October 31, 2018
Last Verified: October 2018
Keywords provided by Louis Tong, Singapore National Eye Centre:
Bacterial microbiome
Gene expression
Additional relevant MeSH terms:
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Dry Eye Syndromes
Keratoconjunctivitis Sicca
Lacrimal Apparatus Diseases
Eye Diseases
Conjunctival Diseases
Corneal Diseases