Swedish Interactive Threshold Algorithm for central visual field defects unrelated to nerve fiber layer

Purpose To evaluate the characteristic appearance of induced central visual field defects unrelated to the nerve fiber layer on standard automated perimetry using the Swedish Interactive Threshold Algorithm (SITA), and to compare the findings to the appearance on existing Full Threshold (FT) and FASTPAC (FP) algorithms. Methods Thirty right eyes of 30 healthy young participants were examined using four Humphrey 24-2 program algorithms: FT, FP, SITA-Standard (SS), and SITA-Fast (SF). Central visual field defects were induced using a high-density white opacity filter centered on a plano lens. The test duration, fovea threshold, mean sensitivity (MS), mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and defect size and depth were compared among all algorithms. Results The mean test duration was 21 % to 71 % shorter (p<0.01), the fovea threshold 0.9 to 2.6 dB higher (p<0.05), MS 1.1 to 1.7 dB higher (p<0.05), MD 0.84 to 1.48 dB higher, PSD 0.33 to 0.60 lower, and VFI 2 % higher (p<0.05) on SS and SF than on FT and FP. The defect size was approximately four points larger and the defect depth 127 to 156 dB shallower on SS and SF than on FT and FP (p<0.01). Conclusions Central visual field defects unrelated to the nerve fiber layer were wider and shallower and global indices were higher on SITA than on conventional FT and FP. These findings indicate that careful attention is required when converting from FT and FP to SITA.