Smartphone Perimetry: Comparison to Standard Automated Perimetry and Assessment of Size-Modulation Strategy with Frequency-Of-Seeing Curves in Healthy Subjects

Abstract

Purpose : Standard automated perimetry (SAP) is a critical visual function assessment tool with well-known limitations; using a smartphone as a perimetry platform could enable inexpensive and home testing, with optimized strategies. Using a method comparison study, we tested the hypotheses that thresholds measured with the Iowa Head Mounted Display perimeter (HMD) agree with a standard perimeter, and that modulating size instead of luminance would produce well-correlated thresholds.

Methods : Fifteen healthy subjects ages 22-33 underwent head-mounted display (HMD) perimetry using the Open Perimetry Interface App on a commercial smartphone, and SAP on the Octopus 900 (O900). Testing was performed at three visual field locations with a stimulus size of 0.43 degrees (Goldmann III) on the HMD and the O900, using the method of constant stimuli. Size-modulation testing was performed at fixed luminance of 1cd/m².

Frequency-of-seeing curves (FOS) were fit from the response data; contrast- or size-threshold was defined as the log(contrast) or log(area) at 50% probability of seen. Statistical analysis included Bland-Altman analysis of threshold agreement between the O900 and HMD, mean threshold and variability comparison with t-test, and linear correlation between luminance-and size-thresholds.

Results : Limits of agreement between HMD and SAP using luminance modulation at comparable backgrounds were -2.9dB to 3.0dB. Thresholds were not different between modalities (mean threshold difference -0.37±1.2dB, p=0.37), with comparable variability. Standardized major axis regression between luminance- and size-thresholds with the HMD showed slope of –6.21 db/log(deg²) (95% CI -5.59—6.91), R²=0.91, p<0.0001.

Conclusions : Contrast thresholds using the HMD showed excellent agreement with the O900. Our results help validate the Iowa HMD perimeter and reiterate the usefulness of FOS curves for such comparisons. Size-modulation, which allows greater stimulus increment resolution on a smartphone display, correlated strongly to contrast modulation. Further testing with glaucoma patients will help determine the usefulness of size-modulation for digital perimetry with smartphone hardware.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure: (A) Comparison of luminance thresholds derived from frequency of seeing curves (B) Pointwise standardized major axis regression comparing size-modulation to luminance-modulation.