Changes in tear film biochemistry in end of day ocular discomfort with and without contact lenses
An estimated 30% of contact lens (CL) wearers suffer from discomfort which is more common and aggravated in the evening. This work examined changes in tear film proteins and lipids, especially those previously associated with non-contact lens dry-eye or inflammation, for their diurnal variation and their association with comfort during CL wear. Comfort decreased at the end of the day, and this was exacerbated by CL wear. Simultaneous quantification of five proteins (lysozyme, lactoferrin, lipocalin 1, prolactin-induced protein and proline rich 4) in 2.5 microlitres of tears was achieved using a novel method based on selected reaction monitoring (SRM) mass spectrometry. The concentrations of prolactin-induced protein, proline rich protein 4, resolvin D1 and C3a are reported for the first time. Concentrations of lysozyme and lactoferrin, secretory phospholipase A2, bradykinin, prostaglandins, cysteinyl leukotrienes, resolvin D1, phosphatidylcholines, lysophosphatidylcholines, sphingomyelins, phosphatidylserines, cholesterol esters, triacylglycerides, wax esters and free cholesterols did not change during the day, during CLs wear and they were not associated with CL comfort. C3 and C3a levels decreased during the day from morning to evening, implying that the classical complement cascade was not associated with discomfort. An end of day decrease in phosphatidylethanolamines and an increase in the concentration of its breakdown product, lysophosphatidylethanolamines, in normal tears was established in these studies. Tear levels of cholesterol esters increased but only during CL wear. The changes in concentration of these lipids were unrelated to comfort. Lipocalin 1 and proline rich protein 4 increased over the day. An increase in prolactin-induced protein (PIP) was associated with end of day ocular discomfort in lens wear and no lens wear but did not change when comparing asymptomatic and symptomatic CL wearers. Leukotrienes B4 level was higher in evening tears of contact lens wearers compared to non-lens wearers and its level was higher in symptomatic CL wearers compared to asymptomatic lens wearers. Overall, the results of these studies suggest that CL-related discomfort is not related to changes in many proteins or lipids in the tear film, but certain components such as PIP and LTB4 may be partly related to comfort during CL wear.
Mass spectrometry, Contact lens, Discomfort
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