GSP uses pattern recognition algorithms in order to assess the visual field results of the patient. For “Normal” and “Glaucomatous” visual fields a risk class can be determined by comparing the detected patterns to the visual field patterns stored in the database of the GSP. If the “Pre-perimetric” risk class dominates the bar chart, it means that the pattern of the measured visual field is similar predominantly to the patterns of patients with pre-perimetric glaucoma from the database. Pre-perimetric glaucoma is defined through glaucomatous changes to the optic nerve head and/or the retinal nerve fibre layer without detectable visual field losses. A “Pre-perimetric” result should be followed by a closer monitoring of the patient.