Lipid, lipase and lipocalin differences between tolerant and intolerant contact lens wearers.
OBJECTIVE
Tear volume is reduced in symptomatic contact lens wearers, evaporation of the ocular tear film may be a cause. In this study we have focussed on symptomatic or intolerant subjects and compared their tear film lipid-related features to those tolerant to soft contact lens wear.


METHODS
Fourteen tolerant and 10 intolerant to lens wear subjects were recruited for this study. Intolerance to lens wear was defined as experiencing dryness symptoms in the first 6 hours of lens wear and consequently not being regular lens wearers. Lipid layer appearance was graded on a 0-5 scale, meibomian gland obstruction was observed, and the McMonnies questionnaire completed. Tears were collected without reflex stimulation. Degraded lipid (tear aldehyde content), secretory phospholipase A2 enzyme (sPLA2) concentration and activity and lipocalin concentration were analysed using spectrophotometry to quantify colour reactions and enzyme linked immunosorbent assays. Statistical results were calculated using non-parametric tests (median +/- interquartile range) or chi-squared test.


RESULTS
Degradation of polyunsaturated fatty acids and related esters leads to the by-products, malondialdehyde and 4-hydroxy-2(E)-nonenal. Intolerant subjects were found to have significantly (p = 0.004) higher concentrations of these by-products in their tears (0.85 +/- 1.0 microM; n = 9) compared to tolerant subjects (0.15 +/- 0.15 microM; n = 10). Intolerant subjects (1.86 +/- 0.05 ng/microl; n = 9) had significantly more (p = 0.047) sPLA2 enzyme in their tears compared with tolerant subjects (1.80 +/- 0.08 ng/microl; n = 12) and significantly more enzyme activity (p = 0.012). Intolerant subjects had significantly higher amounts of lipocalin in their tears (2.40 +/- 1.5 microg/microl; n = 10, p < 0.001) compared to tolerant subjects (0.45 +/- 0.85 microg/microl; n = 13).


CONCLUSIONS
Changes to the components of the tear film, however small, can disturb the nature and dynamics of the tear film. Increased lipases, degraded lipids and lipocalins in the aqueous tear film potentiates intolerance to contact lens wear and was associated with increased McMonnies dry eye history scores and symptoms scores.
Glasson
M
M
Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Kensington, Australia.
Stapleton
F
F
Willcox
M
M
D000328:Adult; D002352:Carrier Proteins / Q000378:metabolism*; D016022:Case-Control Studies; D019411:Clinical Laboratory Techniques; D003261:Contact Lenses / Q000009:adverse effects; D003262:Contact Lenses, Extended-Wear / Q000009:adverse effects*; D015352:Dry Eye Syndromes / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D008049:Lipase / Q000378:metabolism*; D050356:Lipid Metabolism; D054835:Lipocalin 1; D008297:Male; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011446:Prospective Studies; D012016:Reference Values; D013666:Tears / Q000378:metabolism*
D002352:Carrier Proteins; C518443:LCN1 protein, human; D054835:Lipocalin 1; D008049:Lipase; D010741:Phospholipases A; D054467:Phospholipases A2