Methods of mathematical differentiation in tonography

Our bulbar-compressure isotonographical method was applied to 28 normal and 40 glaucomatous eyes. This method was carried out twice on all patients using two pressure gradients: Pt=Po+10 and Pt=Po+30. Also, the outflow facility (C) was determined by Grant's tonography. Thus, 3 C-values were obtained with 3 varying pressure differences (Pt-Po=deltaP). With this differential tonography the mathematical determination and the graphic representation of a real C-value (Cdiff) by deltaP=O are possible. With normal eyes the average C-values were indirectly proportional to the pressure differences. This relationship was found to be directly proportional on glaucomatous eyes. The tonographical coefficients Po/Co-4, P3/CL3-7, Po-10/Co-4, and Po/Cintegral were calculated on 104 normal and 312 glaucomatous eyes. The results show small differences between the average values of the various coefficients for normal and glaucomatous eyes. The percentage of the pathological values on glaucomatous eyes varies from 57.4% to 67.3%. The diagnostic efficiency of the tonography is increased by the determination of Cdiff (percentage of positive values=70%) and the calculation of Po/Cdiff value (95%).