Quantitative comparison of static perimetric strategies in early glaucoma:Test-retest variability

Purpose: The aim of this study is to describe and compare test-retest varia bility of threshold-related suprathreshold and threshold examination strate gies. Methods: Threshold-related suprathreshold and FASTPAC threshold central vis ual field examinations were performed twice (test and retest) within a 4-we ek period on 322 subjects with early to moderate primary open-angle glaucom a and glaucoma suspects. For both strategies, defects were quantified by a count, or score, of the number of defective locations within the field as a whole and by hemifield, thereby providing a simple measure of defect exten t. This quantification was obtained for the suprathreshold strategy at thre e suprathreshold increments (5, 8, and 12 dB) and for the full threshold st rategy at two levels of pattern deviation probability, although absolute fu ll threshold defect depth was not considered. Mean test-retest score differ ences and spread of score differences were used to describe variability. An index of relative variability was used to compare the two visual field exa mination strategies. Results: Marked degrees of defect extent variability were found to exist in both suprathreshold and FASTPAC examination strategies. In general, the su prathreshold strategy exhibited lower test-retest variability of defect ext ent than the FASTPAC strategy. Suprathreshold test variability was dependen t on the suprathreshold increment. FASTPAC examination Variability was inde pendent of defect depth when analyzed on the basis of pattern deviation pro bability values and was also found to be independent of the area of visual field loss. Conclusions: Suprathreshold examination techniques may provide a reliable p erimetric alternative to thresholding strategies for monitoring individuals with early and moderate glaucoma, although they may not be suitable for in dividuals with advanced glaucomatous visual field loss.