Morphology and Repeatability of Automated Perimetry using Stimulus Size VI: A Comparison with Sizes III and V

Abstract

 

Purpose:

 

To describe the visual field of normal subjects using Humphrey perimetry with size VI stimuli and to compare size VI thresholds and retest variability with perimetry using sizes III and V stimuli.

 

Methods:

 

We tested one eye of 60 normal subjects with the Humphrey full threshold algorithm using sizes V (1.72°) and VI (3.44°) stimuli and with SITA-Standard™ using size III stimuli (0.43°). The patients were retested 1-4 weeks later. We compared the mean scores, concentric zones, and point-wise sensitivities among the sizes and their retest variability. Repeated measures ANOVA on Ranks was performed with the dependent variable as sensitivity (dB) of average sensitivity of each eccentric zone.

 

Results:

 

The mean sensitivities were size III: 30.2 ± 1.1; V: 34.4 ± 1.0 and VI 36.0 ± 1.0 (p < 0.001 with all Tukey post hoc paired comparisons significant). Significant differences between the groups were also present for each eccentric zone except 0° for size V vs. size VI. The mean difference on retest across test locations was 1.55 dB ± 1.37 for size III, 1.36 dB ± 1.23 for size V, and 1.27 dB ± 1.15 for size VI. The difference in variability between size III, V and size VI increased with eccentricity, with size III increasing more than the larger stimulus sizes but statistical significance for this difference was not reached. (Figure).

 

Conclusions:

 

The retest variability in normal subjects is slightly less for sizes V and VI full threshold testing compared with size III SITA-Standard™ results and for larger sizes there is a minimal increase with eccentricity.  

 

Keywords: perimetry • visual fields