Comparison of glaucomatous visual field defects using standard full threshold and Swedish interactive threshold algorithms

Objectives: To compare the severity, size, and depth of glaucomatous visual field defects using standard full threshold (FT), Swedish interactive threshold algorithm (SITA) standard (SS), and SITA fast (SF) algorithms of the Humphrey perimeter. Methods: A prospective observational case series of 77 patients with glaucoma performed FT, SS, and SF 30-2 white-on-white testing programs on the same day on 2 occasions for 1 month. The severity of defects was compared using the mean deviation, pattern standard deviation, Advanced Glaucoma Intervention Study, and Hodapp-Anderson-Parrish severity scores. The sizes of defects were compared using the total number of abnormal points on the pattern deviation plot that fit standard criteria for glaucomatous visual field defects. The depths of the defects were compared using the sum of the threshold values for points identified in the pattern deviation plot as fitting criteria for glaucomatous defects. Results: The mean deviations were slightly better using the SS (-9.6±7.1 dB) or the SF (-9.1±6.7 dB) algorithm compared with the FT algorithm (-10.3± 7.1dB) (P<.005). There were no significant differences in pattern standard deviations between SS (8.6±4.0, P=.08) and SF (8.1±3.6, P=.19) compared with FT (8.3±3.3), although the pattern standard deviation was higher in SS fields compared with SF fields (P<.001). Advanced Glaucoma Intervention Study scores were slightly better when the SS (7.5±5.6) or SF (7.2±5.4) algorithm was used compared with the FT algorithm (8.6±5.4) (P<.001). The sizes of glaucomatous defects were slightly larger using the SS (20.9±10.7) algorithm compared with the FT algorithm (19.2±10.9) (P=.004) but not the SF algorithm (20.0±10.6) (P=.11). The depth of defects measured by the SS (220.4±108.0 dB) and SF (219.8±101.3 dB) algorithms was significantly shallower compared with that measured by the FT algorithm (152.3±79.1 dB) (P<.001). There were no significant differences in Hodapp-Anderson-Parrish severity scores among algorithms (P=.12). Conclusions: Glaucomatous defects are measured significantly shallower using the new SITA algorithms but are approximately the same size and severity compared with FT measurements, Care should be taken when using threshold values to compare glaucomatous defects in a patient when converting from FT to SITA algorithms.