Impact of duration of contact lens wear on the structure and function of the meibomian glands

Purpose: To investigate the effects of the duration of contact lens (CL) wear on the meibomian glands (MGs), eyelid and tear film. Methods: This was a cross-sectional study of CL wearers and non-wearers (NWs) aged between 18 and 35 years. The sample comprised of: (i) Three groups of CL wearers of different duration profiles (short, moderate and long experience of CL wear); (ii) a group of previous CL wearers (PWs) who had ceased wear for at least 6 months prior to the present study; (iii) healthy non-wearers as a control group. Study procedures were conducted in the order from least invasive to most invasive as follows: symptom assessment, lipid assessment, non-invasive break-up time, tear meniscus area, tear osmolarity and evaporation, Phenol red thread, MG expressibility, ocular surface and eyelid assessments, meibography, Marx line and lid wiper assessment using lissamine green. For statistical comparison of continuous data, one-way analysis of variance was used with Bonferroni post-hoc correction, where appropriate. Kruskal-Wallis test and Pearson Chi-Square respectively were used for ordinal and categorical variables. Results: A total of 100 participants (49 males and 51 females; mean age +/- SD: 25.4 +/- 4.1) were enrolled across the five groups, such that each was composed of 20 age/sex matched individuals. Significant differences between the study groups were found for MG expressibility (p < 0.001), number of plugged orifices (p = 0.001), number of expressed orifices (p < 0.001), MG dropout (p = 0.001), Marx line score (p < 0.001), palpebral redness (p = 0.003), and roughness (p = 0.002), non-invasive break-up time (p < 0.001), Phenol red thread (p = 0.005), and tear meniscus area (p = 0.029). For all these variables, the NW group was statistically different from all other groups. Duration of wear was not a significant factor, except for Marx line score which was different in PWs compared to those with longer experience of CL wear (p = 0.03) Conclusion: Alterations to MG morphology and function accompany contact lens wear. Although these changes onset during the first 2 years of wear, prolonged CL exposure beyond this point does not appear to be associated with further modification. Cessation of wear for at up to 6 months does not lead to resolution.