The frequency distribution of the glaucoma tolerance limit

The probability of having glaucoma may be expressed by the quotient p = (number of eyes with glaucomatous damage)/(total number of eyes). p has been calculated for different IOP levels, within a total population and also within groups with and without pseudo-exfoliation (PE). The resulting quotients were plotted versus IOP. Random irregularities were reduced by regression analysis, using the equation for the logistic distribution. The resulting sigmoid curves demonstrated that the probability p of having glaucomatous damage at a certain IOP is highest in the PE group. In the total material, the glaucoma probability p was 0.5 at IOP = 27.1 mmHg, and at IOP = 25.3 and 28.0 mmHg in the groups with and without PE, respectively. The frequency distributions of the glaucoma tolerance limit have been computed from the glaucoma probability curves.