Abstract
Purpose :
The commonly used Humphrey Field Analyser (HFA) shows high measurement variability in glaucoma patients, notably at the borders of scotomas, making it difficult to determine if a scotoma is stable or shows progression. It has previously been suggested that this variability may in part be due to gaze instability. By using an eye tracker that compensates for gaze instability, the Compass fundus perimeter (CMP) might lower the variability at scotoma borders. We therefore aimed to determine the test-retest variability of the CMP at the edges of glaucomatous scotomas and compare it with that of the HFA.
Methods :
One eye from each included glaucoma patient was tested with the CMP (24-2 ZEST) and the HFA (24-2 SITA standard) at each of three study days (screening, baseline and follow-up visit) and stratified by mean deviation (MD) into a mild (-6 dB ≤ MD), moderate (-12 dB ≤ MD < -6 dB) or advanced glaucoma stage (MD < -12 dB). Two CMP VF tests were performed at the screening visit for learning purposes. To identify the scotoma borders for each eye, the total deviation plot of the HFA test from the screening visit was used (Figure 1). To assess test-retest variability, the mean absolute difference of the scotoma border points (SBP, i.e., the test points on either side of the scotoma edges) between the baseline and follow-up VF test (3-10 days between tests) was calculated.
Results :
29 eyes (31% women, median (IQR) age 64 (56-72) years) were included for analysis. Median (IQR) time between baseline and follow-up visit was 7 (5-7) days. There were no statistically significant differences in mean absolute SBP difference between the CMP and HFA for all stages combined (1.8 vs 1.9 dB, P = 0.42, Wilcoxon signed ranks test) nor for each glaucoma stage separately (mild: 1.6 vs 1.7 dB, P = 0.70, moderate: 1.8 vs 1.9 dB, P = 0.55, advanced: 1.9 vs 2.2 dB, P = 0.051, Wilcoxon signed ranks test). Figure 2 shows a scatter and density plot of the absolute SBP differences between CMP and HFA.
Conclusions :
CMP and HFA are equally variable at the edges of scotomas with 24-2 VF testing, suggesting that fixation stability with the CMP eye tracker has no advantage over the HFA for detecting progressing scotomas in glaucoma patients by 24-2 VF testing. Studies are warranted to further evaluate the added value of fixation stability on lowering VF test-retest variability in glaucoma patients.
This is a 2021 ARVO Annual Meeting abstract.