Purpose: To determine the effect of an exogenous lipid supplement on the clinical, functional and biochemical aspects of tear film lipid layer in habitual contact lens wearers
Methods: 40 habitual soft contact lens wearers (16 symptomatic, 24 asymptomatic) were recruited to a double-masked, randomized crossover trial with a baseline with no intervention, and 2 intervention visits after using an emulsion drop containing phosphatidylglycerol (PG) or a saline drop as a placebo. Participants used the drops 3 times a day for two weeks with a 24-hour washout period between the intervention and placebo visits. Visits occurred following 14 days of use after 6-8 hours of lens wear. All participants wore Air Optix® contact lenses. Contact lens wear comfort, stability of the tear film (NISDT) and tear evaporation rate (TER) were assessed with lenses in situ. Basal tears (10 μl) were collected to characterize the tear lipidome and to analyze the concentration and activity of phospholipase enzyme (sPLA2) and the concentration of malondialdehyde (MDA).
Results: Symptomatic compared to asymptomatic wearers showed shorter NISDT at baseline (4.2vs6.8 sec p=0.002) and with the placebo drop (2.7vs3.9 sec p=0.03) but not with the use of the lipid drop (4.2vs4.6 sec p>0.05). Symptomatic compared to asymptomatic wearers had higher concentrations of lysophosphatidylethanolamine in tears with the lipid drop (12.2vs5.2 pmol/ μl p=0.04). As the NISDT increased (R2=0.03 p=0.05) and TER decreased (R2=0.08, p=0.001), lens wear comfort improved. An increased concentration of lysophosphatidylcholine reduced comfort (R2=0.12 p=0.03). With longer duration of NISDT, the TER decreased (R2=0.04 p=0.02), the concentration of sPLA2 (R2=0.09 p=0.003) and free cholesterol (R2=0.18 p=0.008) reduced. As the TER increased, there were higher levels of sPLA2 (R2=0.08 p=0.006) and MDA (R2=0.14 p=0.004) in the tears.
Conclusions: Compared with placebo, exogenous phospholipid drops improved the tear film stability in symptomatic wearers. However, the concentration of degraded lipids remained higher in symptomatic wearers compared to asymptomatic wearers with the use of lipid drop. Among the habitual contact lens wearers, improved contact lens wear comfort was associated with longer tear film stability, reduced tear evaporation rate and a lower concentration of degraded lipids.