Abstract
Purpose :
To examine whether there are differences between the tear lipidomes of evaporative (EDE) and non-evaporative (NEDE) dry eye subjects.
Methods :
Ethics was obtained and the trial was registered (ClinicalTrials.gov Identifier: NCT02871440). Forty dry eye subjectswere recruited and designated as dry-eye based on the Ocular Surface Disease Index®(score >18). Subjects were classified as having evaporative or non-evaporative dry eye based on a cut-off value of 67.2gm-2h for tear evaporation rateat a screening visit (EDE = 17 and NEDE = 23). Tears were collected on three occasions using Schirmer strips. Lipids were extracted and analysed using non-targeted liquid chromatography mass spectrometry (LC-MS). Lipid profiles of tears were compared between different days and groups using linear mixed model.
Results :
Thirteen lipid classes were identified and quantified. Individual lipid species were normalized with respect to total lipid in each sample. The percentage of different lipids in the whole population were lysophosphatidylcholines (Median, IQR; 0.11, 0.03-0.42), phosphatidylcholines (2.09, 0.76-5.90), free cholesterol (0.002, 0-0.02), phosphatidylethanolamines (1.42, 0.19-3.34), lysophosphatidylethanolamines (0.66, 0.08-2.87), phosphatidylserines (0.08, 0.01-0.55), cholesteryl esters (4.41, 0.5-25.93), wax esters (37.14, 1.44-60.16), ceramide (0.20, 0.04-0.79), sphingomyelins (0.27, 0.06-1.23), O-acyl-ω-hydroxy fatty acids (0.25, 0.05-1.66), diacylglycerides (0.55, 0.06-1.47) and triacylglycerides (4.17, 0.28-14.0). The percentage of sphingomyelins was different between groups (NEDE vs EDE, 0.67 [0.13-2.08] vs 0.17 [0.05-0.55]; p = 0.02). The percentage of sphingomyelins was significantly different between collection days in NEDE group only (p < 0.05). No other differences were found.
Conclusions :
There were large variations between subjects but not usually between different collection days. There was only a difference in sphingomyelins between the two groups. The results of this study may help in understanding the nature of different types of dry eye.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.