NORMAL VISUAL-FIELDS MEASURED WITH OCTOPUS PROGRAM G1 .1. DIFFERENTIAL LIGHT SENSITIVITY AT INDIVIDUAL TEST LOCATIONS

Exact knowledge of the normal variation of visual fields and the influ ence of age upon them is essential to differentiate normal from abnorm al results, e.g., in glaucoma suspects. This study evaluates the norma l variability of differential light sensitivity at individual test loc ations and incorporates a data base of a multicenter study performed w ith Octopus 201 perimeters using Program G1. The 824 fields thus obtai ned included 139 fields of 139 healthy volunteers who had undergone tw o previous visual fields and completed all three phases of the program . Sensitivity decreased linearly with age, an effect which for individ ual test locations ranged between 0.036 and 0.107 dB/year and which be came more pronounced towards the periphery. On average, the age-relate d effects explained only 17% of the interindividual variation (range 4 %-31%). The interindividual variation within a test averaged 4.6 dB2 a nd revealed a moderate, but quadratic increase towards the periphery. The intra-individual short-term variation was considerably lower, aver aging 2.2 dB2. There was a similar modest, quadratic increase of the i ntra-individual variation towards the periphery. The results may help distinguish incipient disease manifestations from normal variation of perimetric results. Furthermore, the results give insight into the cal culation of global visual field indices.