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Boon or a Bane: Strengths and Pitfalls of Novel Glaucoma Testing Algorithms

Evaluation of visual field (VF) damage remains a mainstay for the clinical diagnosis of glaucoma and assessment of its progression. Recently, new concepts on visual field testing are emerging — to the delight of everyone in the industry.

On Day 4 of the 52nd Annual Scientific Congress of The Royal Australian and New Zealand College of Ophthalmologists (RANZCO Brisbane 2022) during his Glaucoma Update Lecture, Dr. Pradeep Ramulu from the Johns Hopkins Wilmer Eye Institute in the US presented novel concepts in evaluating functional damage in glaucoma, offering evidence-based insights on how to better integrate visual field reliability data into clinical decision making.

Coming in Fast and Furious

Fast or faster glaucoma testing algorithms are able to complete testing in less time, and real-world data has confirmed the advantage of significant speed by comparing faster versus standard test duration. Nevertheless, Dr. Ramulu noted that there may be some pushback against using faster algorithms, as they are thought to be inherently less accurate, show patterns of damage that are not the same, and won’t detect progression as accurately or quickly.

“One study assessing reliability suggested Swedish Interactive Thresholding Algorithm (SITA) Faster is much less reliable than SITA Standard,” he said. Seed point bias described with prior generations of visual field algorithms is more common with SITA Faster.

“You need to be aware of abnormal test quadrants that tested normal with SITA Standard when switching to SITA Faster,” he noted. “False positives are also more common at value range and stage of the disease where they are least impactful. However, limited evidence suggests that these differences in reliability matter.”

Most importantly, according to a study he found, the variability in Standard-Faster VF pairs is similar to Standard-Standard VF pairs whether in mild, moderate or advanced glaucoma.

He added that SITA Faster increases the degree of ‘normal’ in the visual field, but the progression of detection is similar between SITA Standard and SITA Faster. Nevertheless, the benefits of 24-2c over SITA Faster 24-2 are unclear. “There is no evidence of better overall sensitivity or specificity or ability to detect progression,” he shared.

Reliability vs. Speed

Dr. Ramulu thought that the limitations with unreliability need to be weighed against the benefits of faster testing.

“A bottleneck for glaucoma clinics is usually the wait for VF testing — for example, when several patients needing testing arrive in a cluster,” he said. “In my personal experience, the average patient wait time per clinic drops five to 10 minutes with SITA Faster. Assuming you have one wrong decision due to SITA Faster, in 10 clinic days, there will be 25 to 50 hours saved for every one wrong decision.”

In terms of whether the new SITA test pattern of 24-2c is better than the traditional 24-2 field, Dr. Ramulu said that there is no evidence of better overall sensitivity or specificity, or ability to detect progression.

“It only adds about 30 seconds per test, and it probably does pick up more central defects. However, in one study of 25 glaucoma eyes and 25 normal eyes, it did not diagnose glaucoma better,” he shared.

VF in glaucoma is only part of the story. Other aspects to consider are the symptomatic worsening of vision, worsening results on testing and whether the IOP is above target. Based on these points, I make a decision on whether to decrease or continue to the same treatment, use advanced medications, consider laser trabeculoplasty, increase follow-up frequency or consider/push for surgery,” he concluded.

Editor’s Note: A version of this article was first published in Issue 4 of CAKE & PIE POST (52nd RANZCO Brisbane 2022 Edition). The 52nd Annual Scientific Congress of The Royal Australian and New Zealand College of Ophthalmologists (RANZCO Brisbane 2022) was held virtually from February 26 to March 1. Reporting for this story took place during the event.

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