Abstract
Purpose :
The reliability of a scientific measurement is usually estimated from variability across repeated measurements, with standard error (SE) estimating variability in the mean. However, conventional visual field tests are labor intensive, so it is not practical to collect repeated measurements. New at-home tests with redesigned psychophysical procedures have recently made it practical for patients to undertake a “bundle” of 10 tests at home within a period of 5-14 days (Deiner, Damato, & Ou, 2020. Ophthalmology 127:1258) for which a mean and SE can be computed.
Methods :
Patients from the UCSF Glaucoma Clinic were provided a mobile VR headset (Oculus Go, Facebook Inc) running Vivid Vision Perimetry (VVP) software (Vivid Vision Inc, San Francisco, CA). Patients received virtual training while at home and were then asked to perform VVP 10 times within a two-week period at intervals of approximately four months. Tested field locations were arrayed in the Humphrey 24-2 layout. Each location was tested four times per test with a fixed-contrast stimulus chosen to be close to threshold at locations having a sensitivity of 15 dB in conventional HVFA. Percent seen was the dependent variable.
Results :
Between April 2020 and October 2021, 24 patients took 1472 tests in 142 bundles, each containing 5 to 15 tests apiece (mean 10.3, SD 1.9). Percent seen varied from 0% to 100% depending on sensitivity at the location, corresponding to a dynamic range of approximately 5 to 25 dB (HVFA). Mean sensitivity (MS) for each of the 1472 tests was percent seen across 52 locations, not including near the blind spot. Bundle SE was 1.2% on average (std dev 0.9%), corresponding to a test-retest variability of 0.24 dB in HVFA units for the bundle, which compares favorably with the test-retest variability of HVFA in glaucomatous eyes, usually estimated between 0.5 and 1.0 dB. 21 of the bundles contained an outlier (interquartile test); it was generally worse, not better, than the bundle mean. Data review suggested that a change in MS of > 2 SE be used to detect changes in vision.
Conclusions :
The SE for a bundle of visual field tests provides a clinically practical objective measure of test reliability. It quantifies the statistical difference between test epochs when monitoring progressive field loss in diseases like glaucoma.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.