Abstract
Purpose :
Stimulus-evoked photoreceptor outer segment (OS) change has been proposed as an intrinsic optical signal (IOS) source for retinal functional optoretinography (ORG). However, conflicting reports exist regarding light-driven OS elongation and shrinkage. This study aims to verify the light-driven photoreceptor OS shrinkage and light scattering dynamics in human retina.
Methods :
This study has been approved by the Institutional Review Board at University of Illinois Chicago, adhering to the Declaration of Helsinki. Each subject provided informed consent. A custom FF-SS-OCT system with polarization control was developed for selective parallel and cross-polarization imaging. Our recent study shows that the parallel-polarization OCT can sensitively detect ballistic photons from layer-like structures, such as the 1st outer retina band external limiting membrane (ELM), the 2nd band inner/outer segment (IS/OS) junction, and the 3rd band photoreceptor tip, while cross-polarization OCT is dominated by multiply scattered photons. This study employs both parallel and cross-polarization OCT to characterize the OS length changes and light scattering dynamics in light and dark-adapted stages. Stimulation-evoked OS length changes and light scattering dynamics were also evaluated.
Results :
Figure 1 shows representative parallel and cross-polarization OCT intensity profiles acquired at 2o foveal eccentricity, under light and dark conditions. Parallel-polarization OCT revealed that the photoreceptor OS (distance between 2nd to 3rd band) appears to shrink but the sub-retinal space (distance between 3rd to 4th band) increases in light conditions. However, cross-polarization OCT revealed elongated distance between 2nd to 3rd band. Magnitude of the cross-polarization OCT, dominated by multiply scattering light, was observed to be significantly affected by the light condition.
Conclusions :
Parallel-polarization OCT robustly detects the IS/OS junction and OS tip location under light and dark conditions to verify the light-driven photoreceptor OS shrinkage. Whereas, reliable detection of IS/OS junction and OS tip by conventional OCT can be impacted by multiply scattering light. Moreover, magnitude of the cross-polarization OCT can be significantly affected by the light condition. Comparative parallel and cross-polarization OCT promise robust evaluation of light-driven OS length changes and light scattering dynamics.
This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.