[Documentation of glaucomatous visual field defects in threshold and suprathreshold perimetry]

In contrast to normal subjects, the individual stimulus threshold for differential light sensitivity (DLS) in glaucoma patients fluctuates considerably. The sensitivity and the size of the defect are correlated: with a higher individual stimulus threshold, i.e. when sensitivity deteriorates, the number of defects decreases. Conversely, when the individual stimulus threshold drops, i.e. when sensitivity improves, the number of defects recorded increases. The trend is the same with extensive Grade 3 defects. This correlation between sensitivity and defect size means that the number and depth of individual defects change constantly, due to the fluctuation of the individual stimulus threshold. In follow-up examinations test positions with permanent defects (a defects) can be distinguished from those where defects have been detected several times, but not permanently (b defects) and, respectively, only once in 2 1/2 years (c defects). Defects must therefore be classified not only according to depth, but also according to behaviour at individual test positions. Such a classification can be accomplished by tabulating all newly numbered test positions and the defects identified there. After 5 visual field examinations the defects are then classified as a, b, or c defects. They are then identified by colour symbols and transferred to a test position chart representing a synopsis of 5 visual fields. The chart not only permits exact topographical analysis but also furnishes information on certain structural features of the glaucomatous visual field: stable nuclear areas of a defects surrounded by fluctuating peripheral defects (b defects) or concomitant c defects. After a further 1 1/2-2 years, 5 more follow-ups are summarized, classified and transferred to a follow-up test position chart. Comparison of these two test position charts furnishes information of major prognostic value.