Abstract
Purpose :
Optoretinography (ORG) is a novel and non-invasive method for assessing human retinal function and is the optical analogue to electroretinography (ERG), a well-established method for measuring retinal function. Several implementations of ORG using optical coherence tomography (OCT) have been reported. We present progress on a clinically-compatible realization of ORG, wherein a custom-built OCT system is configured to operate similarly to the specifications of commonly-available OCT devices. We demonstrate an ability to extract intensity-based and phase-sensitive measurements of cone photoreceptor in the human retina in vivo.
Methods :
A custom-built spectral domain OCT prototype in the 830nm range was integrated with a visible stimulus channel to perform simultaneous OCT-ORG recording. The stimulus was centered at 550nm, delivered in a flood-illumination manner, and configured to bleach 15% of photopigment. OCT volumes were acquired over 4 seconds in an M-mode fashion (i.e., line scan) at several retinal eccentricities: 2, 4, 6, and 8 degrees nasal from the fovea. The line of retina imaged was approximately 500um in size and sampled at 250 A-scans/B-scan at a B-scan rate of 400Hz, and the power at the cornea was measured to be 0.4mW. Serially acquired OCT B-scans were registered via bulk-motion correction. The outer retinal layers were automatically segmented, and their time-wise amplitude and phase signals extracted for ORG analysis. Velocity-based phase measurements were extracted for each layer to estimate optical path length changes, and intensity-based analysis of the specified layers over time was also conducted.
Results :
Two healthy human volunteers were imaged. Pupil dilation was not required. Each subject was dark-adapted for 3 minutes before OCT imaging. We observed intensity and phase-based changes in the ISOS and COST layers in response to the visible light stimulus. Phase-based measurements suggested a contraction followed by an elongation of the cone photoreceptor layer after stimulation, in line with findings published in the literature.
Conclusions :
This study used a clinically-compatible implementation of OCT-based optoretinography to probe cone photoreceptor function in healthy human retinae. Our work in the near future will apply this experimental setup to patients with retinal degeneration.
This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.