title: A novel technique of contrast-enhanced optical coherence tomography imaging in evaluation of clearance of lipids in human tears.
abstract: OBJECTIVE
  The aim of this work was to gather preliminary data in different conditions of healthy eyes, aqueous tear deficient dry eyes, obstructive meibomian gland disease (MGD) and non-obvious obstructive MGD (NOMGD) individuals, using a new, contrast-enhanced optical coherence tomography (OCT) imaging method to evaluate the clearance of lipids in human tears.
  
  
  METHODS
  Eighty-two adult patients presenting with complaints of ocular irritation were studied for abnormalities of the ocular surface and classified as healthy (n = 21), aqueous tear deficient dry eyes (n = 20), obstructive MGD (n = 15) and NOMGD (n = 26) individuals. A lipid-based tracer, containing an oil-in-water emulsion, was used to obtain an enhanced OCT imaging of the lower tear meniscus. After instillation, a dramatic initial increase of reflectivity of the lower tear meniscus was detected by OCT, followed by a decay back to baseline values over time. Based on this finding, the clearance of lipids was measured in real-time by Fourier-domain anterior segment OCT.
  
  
  RESULTS
  The differences in the clearance of lipids among the four groups as well as the correlations between symptom questionnaire score, standardized visual scale test, fluorescein break-up time, ocular surface fluorescein staining score, Schirmer I test scores were found to be statistically significant. The individual areas under the curve of the clearance of lipids calculated by the receiver operating characteristic curve technique ranged from 0.66 to 0.98, suggesting reliable sensitivity and specificity of lipid-enhanced OCT imaging.
  
  
  CONCLUSIONS
  This new technique of contrast-enhanced OCT imaging of the tear film following lipid-based tracer instillation provides a measure of the clearance of lipids. The quantitative values found are in agreement with other methods of evaluation of the lacrimal system. An improvement of the clinician's ability in the diagnosis and understanding of abnormalities of the ocular surface may be achieved by this simple approach.
authors.affiliation: Department of Surgical Sciences, Eye Clinic, University of Cagliari, Cagliari, Italy.
authors.forename: Pietro Emanuele
authors.initials: PE
authors.lastname: Napoli
authors.affiliation: Department of Surgical Sciences, Eye Clinic, University of Cagliari, Cagliari, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Coronella
authors.affiliation: Department of Surgical Sciences, Eye Clinic, University of Cagliari, Cagliari, Italy.
authors.forename: Giovanni Maria
authors.initials: GM
authors.lastname: Satta
authors.affiliation: Department of Surgical Sciences, Eye Clinic, University of Cagliari, Cagliari, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fossarello
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D002368:Castor Oil / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D005141:Eyelid Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D019793:Fluorescein / Q000378:metabolism; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008297:Male; D008537:Meibomian Glands / Q000378:metabolism; D008875:Middle Aged; D012372:ROC Curve; D011859:Radiography; D013666:Tears / Q000737:chemistry* / Q000378:metabolism; D041623:Tomography, Optical Coherence; D014867:Water / Q000737:chemistry
chemical_list: D003287:Contrast Media; D008055:Lipids; D014867:Water; D002368:Castor Oil; D019793:Fluorescein