Comparison of Compass and Humphrey Perimetry: Test-Retest Variability at Glaucomatous Scotoma edges

The Compass perimeter, despite its integrated eye-tracking, demonstrated similar variability at scotoma borders with 24-2 visual field testing in glaucoma patients compared to the conventional Humphrey Field Analyzer.

Increased variability at the borders of glaucomatous scotomas measured with the Humphrey Field Analyzer (HFA) has been partly attributed to gaze instability. The Compass perimeter (CMP), which incorporates eye tracking to compensate for gaze instability, may reduce variability at scotoma borders. This study determined the test-retest variability (TRV) at scotoma borders measured with the CMP and compared it with that of the HFA.

One eye of each glaucoma patient was tested with both the CMP (24-2 ZEST) and the HFA (24-2 SITA standard) during three visits (screening, baseline, and follow-up). Eyes were stratified by mean deviation (MD) into mild (MD >-6 dB), moderate (-12 dB ≤MD <-6 dB) or advanced glaucoma (MD <-12 dB). Scotoma borders were identified using the HFA total deviation plot from the screening visit. TRV at scotoma edges was defined as the mean absolute difference of scotoma border points (SBP) between baseline and follow-up visual field (VF) tests (3-10 d apart). TRV was compared between devices using the Wilcoxon signed-rank test.

29 eyes (31% women; median [IQR] age 64 [56-72] years) were included. Mean (SD) time between baseline and follow-up was 6.4 (1.3) days. No statistically significant differences in SBP-TRV were found between CMP and HFA for all glaucoma stages combined (1.8 vs. 1.9 dB, P=0.42) or within individual stages.

CMP and HFA show comparable variability at scotoma borders with 24-2 VF testing, indicating no significant advantage of CMP eye tracking in reducing scotoma edge variability.