RESUMO
Prolonged and continuous use of contact lenses for as long as 3 or 4 weeks is common in Mexico due to the low socioeconomic status, poor patient education and self-neglect. Furthermore, wearing contact lenses with low oxygen permeability is common due to their low cost. Thus, patients seek ophthalmologic evaluation due to signs and symptoms of overuse such as red eye, discomfort and tearing. In the present study, the effect of wearing soft contact lenses with a low oxygen permeability on the tear fluid composition after 1 day, 1 week and 1 month without removing them was examined. In this prospective clinical trial, several tear fluid biomarkers were measured in 84 non-adapted contact lens wearers (NACLWs), including the pH, electrolytes, osmolarity, pro-inflammatory molecules [interleukin (IL)-8, IL-1ß and interferon (IFN)-γ], total protein (TP) levels and enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and alkaline phosphatase (AP)]. The results indicated that the tear pH was significantly decreased after 1 day and 1 week; however, after 1 month of use, the tear pH level returned to the baseline. Tear electrolyte analysis demonstrated a significant decrease in Na+ at 1 day, 1 week and 1 month and Cl- levels at 1 week and 1 month, and a significant increase in Ca2+ at 1 week and 1 month, K+ at 1 day, 1 week and 1 month, IL-8 at 1 week and 1 month, IL-1ß only at 1 week and IFN-γ at 1 week and 1 month. Furthermore, the study observed an elevation of TP, AST, LDH and AP levels, however, there were no significant changes in ALT. In conclusion, the current study revealed that continuous wearing of soft contact lenses with low oxygen permeability increase tear fluid proinflammatory cytokine levels and enzymes reflecting tissue damage.
