Frontloaded Visual Field Testing in Glaucoma May Improve Reliability

Frontloaded visual field testing (2 tests per eye on the same visit) may improve the reliability and repeatability of perimetric measurements among patients with glaucoma, according to a study published in Ophthalmology Glaucoma. This protocol may save time, establish baseline visual field function, and be optimal for patients with higher false positive rates and abnormally high sensitivity results, according to the report.

“Frontloading visual fields is likely to be useful in several instances,” the study authors explain. “Firstly, to establish an accurate baseline of visual field function in newly diagnosed patients, a cohort inexperienced with perimetry and prone to higher rates of unreliable results as evaluated using conventionally recommended clinical criteria.”

Researchers included 463 participants (eyes, 902; mean age, 63.6 years; 58.3% men) in a prospective study to compared intra and inter visit outcomes of frontloaded visual field testing using the 24-2 Swedish Interactive Threshold Algorithm-Faster (SFR) paradigm test protocol. Among the eyes included in the study, 56.1% were glaucoma suspects, 31.3% had glaucoma, 10.7% did not have glaucoma, and 1.8% had non glaucomatous optic neuropathy. Study participants underwent 2 visual field tests per eye at baseline and at a follow-up visit conducted a mean 265 days later.

Frontloaded visual field testing showed a high degree of correlation for mean deviation (r, 0.83 for baseline and follow-up assessments; P <.0001) and visual field index (baseline: r, 0.79; follow up, r, 0.81; P <.0001).

A comparison of summary and reliability indices between frontloaded visual field tests 1 and 2 revealed worse mean deviation for test 2 during both visits (-1.28 dB vs -1.59 and -1.28 vs -1.74, respectively). Overall, the difference between pooled tests 1 and 2 differed significantly (mean difference [MD], -0.41 dB; P <.0001). However, the differences in pooled tests from baseline and follow up were not significant (MD, -0.08 dB; P =.62).

Similarly, pooled tests 1 and 2 differed significantly for mean visual field index (MD, -0.18%; P =.03) and for eyes with abnormally high sensitivity in the glaucoma hemifield test (3.2% vs 1.6%; P =.002).

More false positives tests occurred during test 1 at baseline (15.2%) and at follow-up examination (15.5%) compared with tests 2 at baseline (8.8%) and follow-up (9.6%).

Researchers highlight the utility of using frontloaded visual field testing for individuals with glaucoma.

“Distinguishing progression from inherent fluctuations of threshold estimates between visual field tests represents a major clinical challenge in glaucoma,” according to the researchers. “Fluctuations in perimetric performance may mask true progression, especially in individuals prone to higher rates of test-retest variability such as worse baseline MD, higher IOP fluctuation, and faster rates of progression. Establishing a
baseline of visual field function in new patients and detecting progression in subsequent visits therefore requires multiple tests to achieve sufficient statistical power for interpretation.”

Study limitations include a high variability in intervals between visits due to the COVID-19-related restrictions and a single center design.