MODEL FOR OCULAR TEAR FILM FUNCTION

Blepharitis patients have a number of disturbances in their tear film associated with meibomian gland dysfunction that affect evaporation an d tear osmolarity. We tested a series of 156 consecutive patients, wit h a presumed diagnosis of blepharitis, dry eye, or allergic disease, a nd a series of 72 normals. We compared their tear film characteristics using tear osmolarity, tear volume, tear production (fluorophotometri c and Schirmer test), tear turnover (decay constant), tear evaporation , and meibomian gland function evaluated by gland drop-out, expressed lipid viscosity, and volume. Of the 156 patients tested, we found 37 h ad only dry eye, 10 had only allergic disease, 73 had meibomian gland dysfunction and dry eye, and 36 had only meibomian gland dysfunction. We created a model of the relative influence some of these factors had on each other using their correlation coefficients. The highest corre lations for osmolarity were Schirmer test (-0.44), lipid volume low (- 0.44), lipid viscosity high (0.39), gland drop-out (0.39), and tear ev aporation (0.36). With regression analysis we accounted for 47% of the total variation in osmolarity, but only 17% of the variation in tear evaporation. We also present our classification system for blepharitis and dry eye patients based on our measurable physiologic parameters.