Abstract
Purpose :
Detecting early photoreceptor impairment, particularly in degenerative retinal diseases, is challenging in clinical practice. To address this challenge, this study advances split-spectrum amplitude-decorrelation optoretinography (SSADOR) using ultrahigh-speed swept-source optical coherence tomography (SS-OCT). This technology allows for measuring photoreceptor light responses over a record 3 mm x 3 mm field of view at high topographical resolution (~85 um) for the first time, all without the need to resolve and track individual photoreceptor cells. We investigate the wavelength dependency of the SSADOR response, which is expected to reflect the cone spectral sensitivity and their respective density.
Methods :
We designed and built a prototype SS-OCT using a 1 MHz rapid wavelength tunable laser (Thorlabs, Inc., 70 nm bandwidth at 1060 nm), offering an axial resolution of ~7 µm in air. A flash pattern consisting of four colored quadrants (640 nm, 522 nm, 450 nm, and white) was used, as illustrated in the lower left inset of Fig. 1 (A). The scanning pattern includes 5 repeated volumes, with 600 A-scans/B-scan and 600 B-scans/volume. The acquisition time for each volume was 0.6 s. The 0.2-second flash coincides with the beginning of the third OCT volume, resulting in two pre- and two post-flash volumes. Calculating OCT signal variations within the photoreceptor outer segment, the SSADOR algorithm isolated and measured the magnitude of photoreceptor response.
Results :
Four healthy volunteers were recruited. SSADOR imaging was successful in all subjects, demonstrating consistent and reproducible measurements. Figure 1 illustrates a representative SSADOR response map over the parafovea from the 4 colored stimuli presented simultaneously. The red and green stimuli induce comparable responses, while the blue region exhibits the lowest response. The combined red, green, and blue stimuli (white) induced the strongest ORG response compared to individual stimuli.
Conclusions :
The study presents an advanced ultrahigh-speed SS-OCT system to investigate macular optoretinography. The integrated SSADOR algorithm enhances sensitivity to minute changes, enabling photoreceptor response measurement over the largest reported optoretinography field-of-view to date. The advancement potentially leads to a paradigm shift in ophthalmic examination, providing an objective and quantifiable biomarker for macular vision function.
This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.