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E.I. Pearce, L.C. Thai, A. Tomlinson; Changes in tear physiology during the first three months of contact lenses wear . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1579.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The introduction of a contact lens acts as an insult to the tear film. This longitudinal study aims to establish how the tear film of naïve subjects adapts within the first three months of daily contact lens wear. A battery of tear physiological tests was used to assess this adaptation. Methods: Nineteen pathology free subjects (age 31.5 ± 6.7 years), with no history of contact lens wear were recruited. All subjects were fitted with biweekly disposable lenses (etafilcon A) in a daily wear modality. The following parameters were assessed with a new lens in situ at each visit: tear thinning time (TTT, HirCal grid), tear film evaporation rate (TFER, modified Servo Med Evaporimeter) and tear turnover rate (TTR, Fluorotron Master fluorophotometer). Two tear samples were collected by micropipette. One was used to assess osmolality (Clifton Technical Physics Instrument) and the other was analysed for levels of soluble mucin, immunoglobulins, lactoferrin, lipocalin and lysozyme, using size exclusion high performance liquid chromatography (SE–HPLC). All measurements were made at the following time points: first day of wear (D1) and at the end of first week (W1), first month (M1) and third month (M3). Results: All data were tested for normality (Anderson–Darling test). A repeated measure ANOVA was used for the normally distributed data. No significant differences were observed during adaptation for TTT (p = 0.65), TFER (p = 0.64), osmolality (p = 0.54) and TTR (p = 0.81). A non–parametric Friedman Test was used to analyse the tear protein data and significant differences (p < 0.05) were detected. A post–hoc Wilcoxon signed ranks test, with a Bonferroni correction for multiple comparisons, showed significant changes. When compared to D1 levels, the following significant increases in concentration were observed: mucin at M1, immunoglobulins at M3, lactoferrin at M1 and M3, lipocalin at M1 and M3 and lysozyme at W1, M1 and M3. Conclusions: This study shows that the eye does not fully adapt to the insult caused by contact lens wear. It is true that after three months of wear, tear stability, evaporation and production rate showed no change from that seen initially. The one exception was tear composition, where significant increases in tear protein levels were observed with adaptation to lens wear. Therefore, tear composition adapts to lens wear but these changes are not sufficient to be reflected in the functional behaviour of the tear film.
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