The cumulative frequency distribution curve of the eye pressure

Knowledge of the probability of having glaucoma at different levels of eye pressure is a prerequisite for estimating at which eye pressure levels preventive pressure-lowering treatment ought to be applied. The glaucoma tolerance may not be the same in all population groups. Calculation of tolerance distribution curves may be performed if the frequency distribution curves of pressure in eyes with and without glaucoma are known. Regression analysis has been performed to compute curves approaching the cumulative frequency distribution of the eye pressure in different subgroups. Results of a population study including subjects greater than or equal to 65 years of age have been used. An equation describing an asymmetric sigmoid curve has been applied in the curve fitting procedure. The derivative of this equation was used to describe the noncumulative frequency distribution curves. The analysis has been performed in subgroups consisting of normal eyes, glaucomatous eyes, eyes with and without pseudo-exfoliation.