Comparison of virtual field device to humphrey visual field sita-fast in normal subjects

ABSTRACT

Purpose: Humphrey Visual Field (HVF) testing presents challenges for patients with limited mobility. Virtual reality-based visual field testing could provide a practical and portable alternative for visual field testing. This study examines the agreement between Virtual Field (VF), a virtual reality-based visual field test, and HVF. Methods: HVF SITA-Fast and VF BOLT Threshold were performed on both eyes of 40 normal subjects (age 23-66), right eye tested first. The test strategies were randomized. Subjects wore surgical masks in accordance with COVID-19 protocol. Outcome measures included mean deviation (MD), test time and visual field index (VFI). Each patient completed a survey about their experience. Eight eyes were excluded due to unreliable results (FL >20%, FP> 15%). Results: There was not a statistical difference between the right and left eye data on a paired t-test. P-values for HVF were 0.0824, 0.7206, and 0.5663 for MD, VFI and time respectively. P-values for VF were 0.3743, 0.9821, and 0.9872 for MD, VFI and time respectively. The right and left eyes were pooled for analysis. Average MD values were-0.19 dB for HVF and-2.38 dB for VF. Average VFI values were 99.4% for HVF and 96.2% for VF. Average test times were 176.5 sec for HVF and 194.0 sec for VF. When comparing VF to HVF, VF had mean differences (SD) of-2.18 dB (3.36),-3.2% (7.1) and 17.6 sec (39.7) in MD, VFI and time respectively. 95% CIs [-2.98,-1.40], [-4.89,-1.53], and [8.25, 26.89] respectively. All parameters were level dependent on Bland-Altman analysis with greater bias as the results deviated from normal. The bias in MD (mean difference ±SD) was lower for the 29 eyes that did not require trial lenses (-1.0±2.5 dB) than for the 43 eyes that required trial lenses (-3.1± 4.1 dB). 95% CI [-1.90, -0.04], [-4.33, -1.80] respectively. The difference in bias between the two groups was statistically significant (p=0.0163). There was a statistically significant difference (p = 0.0011) between subjects who reported some level of fogging on VF (61.6%) compared to the subjects who reported some level of fogging on HVF (19.4%). Conclusions: VF results did not agree with HVF results. There was more bias between the two tests when a trial lens was required. More subjects experienced fogging of the trial lens on VF than HVF.