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Editors Selection IGR 21-2
Clinical Examination Methods: Perimetric algorithms - 1
Comment by Kouros Nouri-Mahdavi on:
79200 A New SITA Perimetric Threshold Testing Algorithm: Construction and a Multicenter Clinical Study, Heijl A; Patella VM; Chong LX et al., American Journal of Ophthalmology, 2019; 198: 154-165
Heijl and colleagues are to be commended for a very well-designed study that aims to validate an important addition to the Humphrey Field Analyzer's tool box, a new perimetric testing strategy called SITA Faster (SFR) that leads to a 30% reduction in VF testing time, compared with SITA Fast (SF), without a significant increase in measurement variability. There has been a paucity of innovations in the field of perimetry over the last two decades since the introduction of SITA strategy. In the meantime, measuring rates of change in glaucoma has become a topic of interest in both research and clinical settings; as a corollary, more frequent perimetric testing, especially in the first couple of years after diagnosing glaucoma, has been proposed in the hopes of estimating the rates of change more accurately. Although SITA standard (SS) represented a huge improvement in VF testing time, it can take an average of five to seven minutes to carry out in one eye.
The SFR strategy implements seven modifications of the SITA strategy to shorten the test. The main changes involve modifications to the staircase strategy, stimulus timing and starting threshold at primary points, along with elimination of blind spot and false negative catch trials. In this study, Heijl and colleagues, compared SFR to SF and SS in a group of 126 patients with suspected or definitive glaucoma of varying severity who had the same battery of three tests at two separate sessions. Most of the reported outcome measures were similar among all the testing strategies, other than slightly better VFI, on average, on SFR and SF tests compared with SS. Also, the SS strategy tended to flag about 1.1 (± 3.8) more point at p < 1% level on the PD plot. The investigators did not report whether the performance of the SFR strategy varied as a function of eccentricity, but it is reassuring that the measurement variability did not change as a function of the baseline threshold.
SITA Faster (SFR) that leads to a 30% reduction in VF testing time, compared with SITA Fast (SF), without a significant increase in measurement variability
Overall, the results are promising and given the very short testing time (75 ± 31 seconds) with SFR, I predict that many clinicians will adopt the SFR as the strategy of choice in all patients. In the meantime, I would consider using this strategy in patients who have difficulty in performing well with the SS or SF strategy, the elderly, and young patients with short attention span.
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