Comparison of lacrimation kinetics in dry eye patients and normals

A 100 mm long and 5 mm wide filter paper strip enclosed in a transparent plastic sheath to prevent evaporation was used to determine the time dependence of wetting of the strip in the anesthetized eyes of dry eye patients and age-matched normals. Prior to the measurements, the paper strips were extracted by lipid solvents and marked at every millimeter length. Wetted length data were plotted against time and the resulting wetting curves were analyzed to obtain the time dependence of the tear secretion rate during lacrimation. Every eye studied exhibited an exponentially decaying tear secretion rate that could be characterized by three kinetic parameters per cycle: the initial and final tear secretion rates and the secretion decay coefficient. The eyes of the sicca patients showed a much simpler lacrimation pattern than did the controls: 60% of the dry eyes exhibited a one-cycle lacrimation pattern while only 5% of the normal group did so. The tear secretion kinetic parameters characterizing the lacrimation pattern reduced to one-cycle were compared. Both the dry eyes and the control eyes started to lacrimate at about the same high initial secretion rate. However, the lacrimation rate was found to decrease faster and to a lower final rate in dry eye patients as opposed to normal controls.