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Editors Selection IGR 24-1

Clinical Examination Methods: Suprathreshold Perimetry revisited

Comment by Kouros Nouri-Mahdavi on:

Monitoring of advanced glaucoma remains a major unmet need in the field of diagnostics. Clinicians have mostly relied on changing to a larger stimulus size or focusing on the remaining central visual field (VF) to monitor such patients. Denniss and colleagues lay the foundation for a completely different approach to this problem, namely measuring the remaining VF using a suprathreshold strategy at higher resolution. They compare the performance of two candidate strategies in a simulation study to that of Humphrey's Full Threshold (FT) strategy.

The first algorithm, Spatial Binary Search (SpaBS), presents 20-dB stimuli at each standard 24-2 VF location and creates new points at the border of the seen/unseen points until all neighboring locations are matched with regard to their seen/unseen response or until tested points are adjacent. The second algorithm, SupraThreshold Adaptive Mapping Procedure (STAMP), presents 20-dB stimuli at (new) locations where acquired information (entropy) would be maximized. Testing was stopped after a fixed number of presentations estimated as 50%‐100% of a SITA Standard test. Measurements were carried out down to 1.5° resolution with both approaches. Interpolated data from FT VFs were used as the external standard. The percentage of locations in the simulated VF whose seen/unseen status matched that of the reference VF and repeatability and accuracy averaged over 200 repeated simulations were then compared.

Overall, the STAMP strategy, regardless of time restrictions imposed, had higher accuracy and repeatability than SpaBS and performed similarly to FT strategy. Visual field MD values did not affect performance of the two algorithms. STAMP repeatability began to exceed that of FT strategy when STAMP used more than 70% of the number of presentations a SITA Standard test would make. The researchers concluded that the SpaBS approach was not worthy of further consideration. STAMP could potentially provide high-resolution spatial measurements of the VF with a test duration 50% to 70% of SITA standard.

The suprathreshold approach proposed by Denniss et al. is promising and certainly worth further investigation in glaucoma patients; it may add an important tool to our armamentarium for monitoring glaucoma in advanced stages. Variants of this strategy could be used in earlier stages of glaucoma for assessing VF regions beyond the customary 24°, which have been largely ignored after switching to automated perimetry. One could also imagine using a sliding-scale cutoff for this strategy depending on the baseline measured sensitivity.

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