Interactions between ocular surface fluid and cornea related to contact lenses

PURPOSE. TO improve the quantification of damage to the ocular surface, met abolite levels, electrolyte concentrations, and enzyme activities were assa yed in corneal epithelium, stroma and tears. METHODS. In rabbits, rinsing or contact lenses were used to induce microtra uma. For more severe trauma, experimental injuries were induced with 1 N Na OH. Human accidents included epithelial lesions and mild chemical burns. En zymatic test systems and electron dispersive X-ray analyses (EDXA) were emp loyed. Corneal hydration was assessed by wet and dry weights. Interleukins were analysed with ELISA. RESULTS. In contrast to normal eyes, in ocular surface trauma the interacti on between tear fluid and cornea played an important part. After wearing co ntact lenses or rinsing, glucose and lactate levels in the cornea and in te ars increased, and ATP and glycogen in the cornea decreased. After epitheli al lesions, N-acetylglucose aminidase (NAcGA, E.C.3.2.1.50) was released in to the tears. Epithelial defects alone and - much more - rinsing the denude d stromal surface produced an increase of lactate and glucose in tears and a dramatic fall in Na, CI, and S levels in the stroma. Rinsing with phospha te induced corneal calcification. IL-l and IL-6 were increased in human cor neal buttons from patients with trauma and inflammation. CONCLUSIONS. Biochemical analyses may be useful to quantify trauma to the o cular surface.