Validation of the Iowa Head-Mounted Open-Source Perimeter

Abstract

Purpose: To assess the validity of visual field (VF) results from the Iowa Head-Mounted Display (HMD) Open-Source Perimeter and to test the hypothesis that VF defects and test-retest repeatability are similar between the HMD and Octopus 900 perimeters.

Methods: We tested 20 healthy and nine glaucoma patients on the HMD and Octopus 900 perimeters using the Open Perimetry Interface platform with size V stimuli, a custom grid spanning the central 26° of the VF, and a ZEST thresholding algorithm. Historical data from the Humphrey Field Analyzer (HFA) were also analyzed. Repeatability was analyzed with the repeatability coefficient (RC), and VF defect detection was determined through side-by-side comparisons.

Results: The pointwise RCs were 2.6 dB and 3.4 dB for the HMD and Octopus 900 perimeters in ocular healthy subjects, respectively. Likewise, the RCs were 4.2 dB and 3.5 dB, respectively, in glaucomatous patients. Limits of agreement between the HMD and Octopus 900 perimeters were ±4.6 dB (mean difference, 0.4 dB) for healthy patients and ±8.9 dB (mean difference, 0.1 dB) for glaucomatous patients. Retrospective analysis showed that pointwise RCs on the HFA2 perimeter were between 3.4 and 3.7 dB for healthy patients and between 3.9 and 4.7 dB for glaucoma patients. VF defects were similar between the HMD and Octopus 900 for glaucoma subjects.

Conclusions: The Iowa Virtual Reality HMD Open-Source Perimeter is as repeatable as the Octopus 900 perimeter and is a more portable and less expensive alternative than traditional perimeters.

Translational relevance: This study demonstrates the validity of the visual field results from the Iowa HMD Open-Source Perimeter which may help expand perimetry access.

Figure 1.

Custom visual field testing grid used from the OPI software. Shading indicates the zones used for analysis as discussed in Methods. Zones 1, 2, and 3 were 2.8° to 10°, 11.3° to 20.4°, and 21.4° to 28.2° from center fixation, respectively.

Figure 2.

Pointwise Bland–Altman plots for arm 1 of the study for both the Octopus 900 and HMD perimeters. Both devices were controlled through the Open Perimetry Interface using the ZEST thresholding algorithm, Central 26 grid pattern, and Goldmann size V stimuli. Sensitivities less than 20 dB were censored.

Figure 3.

Pointwise Bland–Altman plots directly comparing the HMD perimeter to the Octopus 900 perimeter. Both devices were controlled through the OPI using the ZEST thresholding algorithm, Central 26 grid pattern, and Goldmann size V stimuli. Sensitivities less than 20 dB were censored.

Figure 4.

HMD frequency-of-seeing curves for central, mid-peripheral, and peripheral locations using Goldmann size V stimuli. Stimulus contrast levels are presented as HFA-equivalent decibels. A ceiling effect is seen for central locations, subsequently lifted with use of a neutral density filter.