Abstract
Purpose :
OCT-based optoretinography (ORG) has revealed light-evoked changes in photoreceptor outer segment (OS) length. These are thought to be partly osmotically driven, and may cause water movement outside the OS as well. Here we use a custom, proto-clinical OCT-ORG system to measure changes in the subretinal space (SRS). Changes in SRS volume could be linked to clinically significant factors such as permeability of the RPE-Bruchs complex, and may be an independent assay of retinal health and disease.
Methods :
A previously described OCT system [Vienola et al., Optica, 2022] was used to image three normal retinas after dark adaptation. A 554 nm wavelength LED flash was used, which stimulated the majority (L and M) of cones equally. Serial B-scans were obtained at 400 Hz, with a visible flash delivered after 40 ms. Measurements were performed 2 degrees from the foveal center. Resulting B-scans were divided into rolling blocks of 5, phase corrected using a histogram approach, and used to determine phase velocities of the IS/OS, COST, and RPE layers. The relative velocities were used to determine rates of length change in the OS and SRS at multiple ROIs. By tracking these over time, changes could be observed in response to the stimulus flash. This study adhered to the Declaration of Helsinki.
Results :
As shown in Fig. 1, the SRS exhibits an expansion during ~5ms after the flash, followed by a slower contraction. These changes are complementary to the OS changes.
Conclusions :
We have measured ORG responses of OS and SRS using standard OCT, showing that layers of the retina other than OS exhibit light-evoked changes in volume. Whether they are complementary in disease-affected retinas is unknown and a topic for future investigation, as are the responses of these layers at rod-dominant eccentricities and to flicker stimuli.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.