JAN 06, 2022
Investigators studied whether changing test strategies from Swedish Interactive Thresholding Algorithm (SITA) Standard to SITA Faster had an effect on visual field (VF) performance and would vary according to glaucoma severity.
This retrospective, longitudinal, study included 421 patients (766 eyes) with manifest or suspected glaucoma undergoing a sequence of VF examinations during routine care. Patients first received SITA Standard followed by SITA Standard again, and then SITA Standard followed by SITA Faster (mean of 13.9 months between tests). Intra-eye comparisons were made between the first 2 and last 2 tests. Difference in the change in mean deviation between the second and first examinations (∆MD) was calculated as the primary dependent variable, with the primary independent variable being the VF sequence (Standard-Standard or Standard-Faster). The main outcome measure was the difference in ∆MD between the Standard-Standard and Standard-Faster sequences, stratified by disease severity.
While there was no significant difference in ∆MD between the Standard-Faster and Standard-Standard sequences in eyes with mild glaucoma (−0.23 dB), the Standard-Faster sequence was associated with a 0.87 dB difference in ∆MD compared with the Standard-Standard sequence in eyes with moderate glaucoma, and a 1.49 dB difference in ∆MD in eyes with advanced glaucoma. The SITA Faster tests had a shorter mean test duration than the SITA standard tests but also a greater percentage of false positives.
Limitations of the study include the potential for selection bias, the possibility of a learning effect for exam-naïve patients without prior perimetric testing experience, and that ∆MD was the only metric used to monitor disease progression.
Changing the testing strategy from SITA Standard to SITA Faster in eyes with moderate or advanced glaucoma may cause difficulty in detecting worsening disease in those with more severe disease at baseline. As a result, clinicians should consider this patient population when choosing a testing strategy. One reason SITA Faster resulted in increased MD in eyes with moderate and advanced glaucoma is that higher sensitivity and MD values are found with faster perimetric tests, and these are amplified in eyes with more severe disease due to visual fatigue. Faster tests also may underestimate MD more than standard or full threshold tests, and there may be increased error-related factor cutoffs with SITA Faster than with SITA Standard. The overlap in the distribution of ∆MD between the two sequences and individual variance in ∆MD make it difficult to account for differences in testing strategy.