Detection of field loss and of changes in the disturbed visual field are the 2 important points for the glaucoma patient. Deterioration in visual fields demands a change in therapeutic approach and may be decisive for whether or not surgery is to be carried out. But how accurately can changes in the visual field be determined? With the trial version of an analytical program (Delta) developed by Bebie and Fankhauser, the changes in the 30.degree. visual field (Octopus program no. 31) of 125 eyes in 66 patients with chronic simple glaucoma or ocular hypertension, pseudoexfoliation glaucoma and pigmentary glaucoma were analyzed. The mean age of the patients was 61.2 .+-. 11.3 yr. The mean feature of analytical program Delta is that it allows comparison of 1-6 visual fields as determined by Octopus program no. 31 or 33, observed over a time period A, with 1-6 fields from a time period B, as well as allowing these visual fields to be characterized.