Transverse chromatic offsets with pupil displacements in the human eye: sources of variability and methods for real-time correction

Abstract

Tracking SLO systems equipped to perform retinally targeted stimulus delivery typically use near-IR wavelengths for retinal imaging and eye tracking and visible wavelengths for stimulation. The lateral offsets between wavelengths caused by transverse chromatic aberration (TCA) must be carefully corrected in order to deliver targeted stimuli to the correct location on the retina. However, both the magnitude and direction of the TCA offset is dependent on the position of the eye's pupil relative to the incoming beam, and thus can change dynamically within an experimental session without proper control of the pupil position. The goals of this study were twofold: 1) To assess sources of variability in TCA alignments as a function of pupil displacements in an SLO and 2) To demonstrate a novel method for real-time correction of chromatic offsets. To summarize, we found substantial between-and within-subject variability in TCA in the presence of monochromatic aberrations. When adaptive optics was used to fully correct for monochromatic aberrations, variability both within and between observers was minimized. In a second experiment, we demonstrate that pupil tracking can be used to update stimulus delivery in the SLO in real time to correct for variability in chromatic offsets with pupil displacements.

Eye tracking-based estimation and compensation of chromatic offsets for multi-wavelength retinal microstimulation with foveal cone precision

“…This relationship was experimentally confirmed in previous studies [14,18], and applied to a method to infer TCO from pupil position, yet without focusing on the precision necessary to target single cones [19]. We here employ high-resolution eye tracking to demonstrate that transverse chromatic offsets can be compensated in real time to ensure cell sized precision during single cell psychophysical experiments on cones of the central fovea or rods.…”

“…Many eye trackers use pupil coordinates such as its center to report absolute eye position, and the pupil center has been shown to coarsely correlate with objective measures of TCA [14,18,19]. For precise estimates of TCA, however, the location of the TCA-inducing beams relative to the eye’s optics - and not its pupil - is more relevant [24].…”

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

“…The practical implications are that one can achieve foveal cone resolution in both 543 nm and 680 nm spectral channel when the correction is informed by the measurements of the eye's ocular aberrations at 940 nm. This study shows the practical limits of the different spectral channels and that both 680 nm and 543 nm imaging can be used for structural foveal imaging, psychophysical experiments in the fovea [11] and measuring and correcting for TCA [13,14].…”

“…corneal curvature). The transverse chromatic aberration, or TCA, of the eye has also been studied [9,10] and recently objective techniques to measure it [11,12] and correct it [13,14] have been employed. The extent to which the high order aberrations of the eye change with wavelength is less studied.…”

Ray tracing 3D spectral scenes through human optics models

“…The ISET3d in each row show the TCA at 0, 8 and 15 eccentricity. The two rows were calculated after modifying the anterior chamber depth (ACD) of the Navarro eye within anatomical limits (Rabsilber et al, 2006;Boehm et al, 2018). (B) The ACD is set to 3.29 mm.…”