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Editors Selection IGR 21-3

Clinical Examination Methods: Comparing Perimetric Approaches I

Comment by David Crabb & Giovanni Montesano on:

90421 A Comparison of the Visual Field Parameters of SITA Faster and SITA Standard Strategies in Glaucoma, Lavanya R; Riyazuddin M; Dasari S et al., Journal of Glaucoma, 2020; 29: 783-788

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Static automated perimetry (SAP) is one of the cardinal examinations in the diagnosis and follow-up of glaucoma. Despite its widespread use and its paramount importance in measuring people's real visual function, SAP has seen little innovation since first conceived. Nonetheless, the need for improvements is felt strongly by clinicians and patients alike, especially on one crucial aspect: reducing test time.

Lavanya et al. evaluate SAP examinations obtained with a Humphrey Field Analyzer (HFA, Zeiss Meditec, Dublin, CA, USA) using two different implementations of the Swedish Interactive Thresholding Algorithm (SITA), SITA-Standard and SITA-Faster, in a cohort of healthy participants (eight eyes) and glaucoma patients (89 eyes). Results from SITAStandard are usually regarded as a reference standard for glaucoma care, but SITA-Fast and its latest iteration, SITA-Faster, are designed to produce results in a shorter test time. Results from Lavanya et al. confirm this; median test duration was 55% shorter with SITA-Faster. The authors then partially address an important clinical question: are the results of the two tests equivalent? The conclusion is a resounding maybe.

The conclusion is a resounding maybe.

Despite good agreement in terms of global indices and sensitivity values, their results provide no information on the relative diagnostic ability of the two strategies. Evaluation of test-retest variability was performed on a smaller subset (11 eyes), too few to draw any reliable conclusions. Since perimetric measurement variability (noise) hampers the accurate detection and monitoring of glaucomatous visual field damage, assessing the average agreement between the two tests is useful but not conclusive to assess equivalence in clinical practice.

We should reflect on how such shorter test times are achieved. As noted by the authors, the original SITA-Fast traded speed for some accuracy by altering the termination criteria for the test. Instead, SITA-Faster further shortened the assessment by eliminating ancillary checks, such as blind spot presentations and false negative catch trials, both long been deemed to not be clinically useful.¹ There is no reason why these same modifications could not be applied to the original SITA-Standard, achieving faster tests without compromising precision. As a clinical community, we need to shape and drive technological innovation, willing to sacrifice the necessary amount of accuracy for practicality, but not more.

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