Measuring and modeling entoptic patterns induced by structured states of light

Abstract

Purpose : Perception of uniformly polarized light in the form of a Haidinger’s Brush may be sensitive to macular pigment changes that occur early in retinal degeneration, but this phenomenon is difficult to see and offers limited clinical utility. Structured light enables larger and more detailed entoptic images that can be used in psychophysical tasks. The aim of this study was to model psychophysical data relating to the spatial extent of structured light entoptic images to estimate macular pigment optical density (MPOD). This method may allow for the rapid spatial profiling of macular properties, enabling earlier disease detection.

Methods : Orbital angular momentum (OAM) states of light were used to induce a series of entoptic azimuthally varying fringes (3, 8, 11, 13, and 18 fringes) which rotated clockwise or counterclockwise. Similarly, we created entoptic ring patterns with periods of 0.90°, 1.35°, 1.80°, and 2.15°, moving inward or outward from the center. The center of the stimuli was masked and the mask radius varied using a staircase algorithm to estimate 71% accuracy for discrimination of motion direction (n = 24 participants with normal vision). The threshold radius was converted to degrees of visual angle using a retinal image taken with structured light. Spatiotemporal energy modeling of the psychophysical data allowed us to model differences in the contrast and radius of entoptic percepts by varying the radius and amplitude of MPOD.

Results : Entoptic threshold image sizes ranged from 1° to 15°. For the OAM states, average percept radius increased by 0.4° for each additional fringe (R² = 0.91). The radial ring state's apparent radius decreased by 2.3° as the ring period increased by 1° of visual angle (R² = 0.86). Spatiotemporal energy modeling suggested that individual variance in performance can be predicted by varying the MPOD distribution used to generate entoptic images.

Conclusions : Spatiotemporal energy modelling suggests that individual differences in entoptic image size can be attributed to differences in MPOD.

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

 

(Left) Pattern size from the staircase estimator, varying the number of azimuthal fringes on the x-axis. (Right) Modeling results for entoptic azimuthal fringes compared to data from one subject.

 

(Left) Pattern size from the staircase estimator, varying the period of concentric rings on the x-axis. (Right) Modeling results for entoptic radial rings compared to data from one subject.